滇杨(Populus yunnanensis)对增强紫外辐射、干旱和喷施脱落酸的生态生理响应

目前，随着全球气候变化的加剧，水分短缺更加明显。在干旱与半干旱地区，水分胁迫是影响植物存活和生长的主要限制因子。同时，随着大气平流层中臭氧浓度的减少，过量的紫外辐射(UV-B)到达地球表面，一些地区的植物不可避免地受到增强UV-B 和水分胁迫的共同作用。文献表明在UV-B 增强的情况下，干旱表现为减弱或增强UV-B 对植物的影响，这与种、品种有一定的相关性。另外，脱落酸(ABA)是近年来研究报道最多的信息调控物质，与植物抗旱性途径有较大的关系，但其对植株抗UV-B 的影响还有待于研究。本论文以滇杨(Populus yunnanensis)为模式植物，从形态和生理方面研究了增强UV-B、干旱和脱落酸对它的影响，并探讨了UV-B 与干旱的互作效应以及喷施脱落酸对植株抗旱性和抗UV-B 能力的影响。主要研究结果如下：1. 增强的UV-B 和干旱胁迫都影响了滇杨的形态生长和生理生化反应。它们都导致了滇杨植株的株高、基茎、整株叶面积、平均叶面积、总生物量和净光合速率的显著降低，使得叶片增厚，过氧化物酶(GPX)活性升高，脯氨酸和花色素苷含量增加，膜脂过氧化程度增大。不同的是干旱显著降低了植株叶片数目，增大了根/冠比(Rs)、细根/总根比(Ft)、提高了内源ABA 含量、碳同位素(δ13C)以及紫外吸收物质含量和超氧化物歧化酶(SOD)的活性，而UV-B 对它们没有影响。干旱与UV-B 的复合作用加剧了任一单独胁迫对植株的抑制，表现为更小的株高、基茎、整株叶面积、平均叶面积、总生物量，更低的光合作用和更高的MDA 含量。而且UV-B 辐射降低了干旱胁迫下生物量分配的可塑性，表现为降低了干旱情况下的Rs 和Ft，ABA 的含量也显著下降，复合胁迫下脯氨酸含量和过氧化氢酶(CAT)的活性比任一单独胁迫时都要低。这些实验结果表明，增强的UV-B 与干旱的复合胁迫加剧了对植株的抑制作用。II2. 干旱情况下同时施加外源ABA 提高了植株的根/冠比、细根/总根比和单位面积叶重，即提高了干旱胁迫下植株对生物量分配的可塑性。而且外源ABA 使干旱胁迫下的长期用水效率、ABA 含量、脯氨酸含量、GPX 活性进一步增加，并有效调节了活性氧代谢的平衡，抑制了受旱植株MDA 的增加。结果表明，外源ABA 的喷施提高了滇杨植株的抗旱性。3. 在增强的UV-B 情况下，外源ABA 加剧了UV-B 对滇杨形态生长的抑制效果，表现为进一步降低了滇杨植株的整株叶面积、平均叶面积、单位面积叶重和总生物量，而且ABA 还降低了UV-B 胁迫下的净光合速率和脯氨酸的含量，增大了MDA 的含量。通过以上的数据我们可以看出，外源ABA 虽然提高了滇杨植株的抗旱性，但却加剧了UV-B 胁迫对植株的抑制作用。Currently, drought is one of the most serious environmental stresses. In arid and semi-aridregions, drought is a major constraint imposed on tree survival and growth. The decrease ofozone layer leads to a significant increase in ultraviolet-B (UV-B, 280-320 nm) radiationreaching the earth surface. In some places, plants suffer both UV-B and water stresssimultaneously. Their combination will increase or decrease the sensitivity of plants to UV-Bstress which lies on the species. On the other hand, abscisic acid (ABA), as a plant homoneand growth regulator, is better for plants resistant to drought stress, but it is uncleared aboutthe relationship between exogenous ABA and supplemental UV-B. In the present study, weemployed Populus yunnanensis Dode as a model species to characterize the growth andecophysiological responses of woody plants to supplemental UV-B, drought and exogenous ABA. The results are as follows:1. Both supplemental UV-B and drought affected the morphological, physiological andbiochemical responses of P. yunnanensis. They decreased the plant height, basal diameter,total leaf area, average leaf area, biomass and photosynthesis, and increased specific leaf mass,the activity of guaiacol peroxidase (GPX), the content of proline, anthocyanins andmalondialdehyde (MDA). However, drought decreased the leaf number and increasedroot/shoot ratio, fine root/total ratio, the activity of superoxide dimutase (SOD) and thecontents of ABA, carbon isotope composition (δ13C), UV-absorbing compounds. Whilesupplemental UV-B had no effects on them. The combination of drought and UV-Baugmented the growth inhibtion acting as further lower plant height and smaller basaldiameter, leaf area, biomass and higher MDA content. And compared with drought stress,root/shoot ratio and fine root/total root ratio decreased under the combination stresses. The photosynthesis, proline content and Catalase (CAT) activity became lower under combinationstresses than that of either stress lonely. According to these results, we suggested that,compared with the effect of stress lonely, the combination of supplemental UV-B and droughtdid not mitigate the harmful effect, but augmented it.2. Under drought conditions, exogenous ABA increased root/shoot ratio, fine root/total rootratio and the specific leaf mass. That was to say exogenous ABA increased plant plasticityunder drought conditions. Also ABA content, proline content, activity of GPX and δ13C wereenhanced further. In addition the enhancement of MDA was restrained. So the resultssuggested that exogenous ABA increased the seedling capacity of resistance to drought.3. Under supplemental UV-B conditions, exogenous ABA augmented the growth restrain ofUV-B to seedlings, which acted as further decreased leaf area, specific leaf mass and biomass.Compared with UV-B stress alone, proline content and photosynthesis were decreased andMDA content was increased under the combination of UV-B and ABA. These resultssuggested that although exogenous ABA increased the seedling capacity of resistance todrought, it augmented the growth restrain of supplemental UV-B to P. yunnanensis.

遮荫与外源脱落酸喷施对青杨(Populus cathayana Rehd.)不同种群抗旱性的影响

杨树具有分布广、适应性强的特征，在生态环境治理和解决木材短缺方面均占有重要位置。青杨(Populus cathayana Rehd.)是青杨派树种的重要成员之一，也是生长较迅速、易繁殖的重要杨树资源。本研究选取了来自不同气候地区的青杨两种群为材料，采用植物生态学、生理学和生物化学的研究方法，系统地研究了青杨对干旱与遮荫、干旱与外源脱落酸(ABA)喷施的生长、形态、生理和生化响应及种群间差异，研究成果可为我国干旱半干旱地区的造林以及生态恢复提供理论依据和科学指导。主要研究结论如下：1.青杨在干旱胁迫下的适应机制为：生长性状及生物量的分配变化：干旱胁迫下虽然植株生长受抑，株高、基茎及各部分生物量都显著减小，但有相对较多的生物量向根部分配，根/冠比以及细/粗根比增加。青杨对干旱胁迫的光合作用表现为：干旱胁迫降低了青杨的净光合速率、蒸腾速率、气孔导度以及光合氮利用效率，提高了瞬时用水效率。干旱还引起了活性氧的产生，使得膜脂过氧化产物丙二醛(MDA)增加，同时也增强了植物抗氧化酶系统(如超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)活性的增加)及非酶系统的能力(如抗坏血酸(AsA)含量的增加)。干旱降低了植物叶片的相对含水量，而促进了渗透调节物质(游离脯氨酸及可溶性糖)的积累，增加了植物的渗调能力。干旱下青杨两种群的内源ABA含量显著增加，碳同位素组分(δ13C)也显著提高。这些结果证明植物遭受干旱胁迫后发生一系列的形态、生理和生化响应，这些变化能提高植物在干旱下的存活和生长能力。2.青杨两种群对干旱胁迫反应的种群差异：与来自湿润地区的汉源种群相比，来自干旱地区的乐都种群在干旱条件下生物量向根系分配的可塑性更强，同时具有更强的抗氧化系统能力，所受到活性氧的伤害也更少，并且累积更多的脯胺酸和ABA，具有更高的δ13C。这些都说明了乐都种群对干旱的适应性比汉源种群更强。两种群对干旱的响应差异应归于它们的用水策略的不同：汉源种群来自湿润地区，采用了耗水型的用水策略，抗旱能力较弱；而乐都种群，来自干旱地区，通常采用节水型的用水策略，有更强的抗旱能力。3.遮荫对青杨两种群抗旱性的影响：遮荫对青杨抗旱性的影响决定于遮荫程度的不同，我们的结果表明中度的遮荫可以有效的提高干旱下植物的生长，对干旱胁迫有明显的缓解作用，具体体现在中度遮荫下受旱植物的叶片相对含水量得到提高，使得植物体内水分状况得到了改善；光合速率并未降低，植物光合氮利用效率增加，说明中度的遮荫并未明显限制植物的碳获得；抗氧化酶活性与膜脂过氧化产物MDA含量的同时降低，说明中度遮荫下所受到的活性氧伤害减少；中度遮荫下的ABA及δ13C的变化也不如在全光下变化明显，这也说明中度遮荫缓解了干旱胁迫。但是重度的遮荫却对干旱胁迫有明显的加剧作用，主要表现在重度遮荫降低了植物的光合速率，严重抑制了植物的生长；同时重度遮荫下脯胺酸含量和抗氧化酶活性的急剧下降，导致了植物渗调能力的下降及膜脂过氧化产物MDA的显著升高；重度遮荫还显著降低了内源ABA的累积和δ13C，降低了植物的抗旱能力。此外，青杨两种群在对干旱和遮荫的响应中，也表现出种群差异。汉源种群，来自湿润且年日照辐射较少的地区，表现出相对更强的耐荫性和需水性。而乐都种群，来自干旱且年日照辐射丰富的地区，表现出相对更强的耐旱性和需光性。这说明了植物对环境胁迫的耐受性是其长期适应原生境的结果，并且来自不同气候地区的两种群在面临环境胁迫时会采取不同的生存策略。4. 外源ABA喷施对青杨两种群抗旱性的影响：外源ABA的喷施可以提高两种群的抗旱性，具体表现为外源ABA喷施促进了青杨根系的生长，显著提高了干旱下植物的根/冠比和细/粗根比，减少了比叶面积；在生理生化方面，外源ABA降低了干旱下植物叶片的气孔导度，降低了蒸腾速率和净光合速率，但提高了瞬时用水效率，提高了叶片的相对含水量，增加了干旱下植物的保水能力。外源ABA进一步增加了干旱下植物内源ABA的积累，促进了植物渗调物质如脯胺酸和可溶性糖的积累，增加了抗氧化酶系统(如SOD、APX、CAT)的活性和非酶系统AsA的含量，降低了活性氧(如超氧阴离子(O2和过氧化氢(H2O2))对植株的伤害。此外，外源ABA还进一步提高了干旱下植物的δ13C，提高了植物的长期用水效率，由此提高了植物的抗旱能力。另一方面，两种群对外源ABA和干旱的响应也有所差别。来自湿润地区的汉源种群，对干旱较为敏感，所受干旱的影响也较大，而外源ABA的喷施对汉源种群抗旱性的提高作用也更为突出。乐都种群，由于其长期适应干旱地区的生长，本身已具有较强的抗旱能力，因此外源ABA喷施对其抗旱性的提高不如对汉源种群的效果明显。由此我们可以得出对于一些抗性弱或干旱敏感的物种或者种群，可以采用外施ABA的方法来提高其抗性。Poplars play an important role in lumber supply, and are important component ofecosystems due to their wide distribution and well adaptation. Populus cathayana Rehd.,which belongs to Populus Sect. Tacamahaca Spach, is one of the most important resources ofpoplars for its fast growth and reproductive. In this study, different populations of P.cathayana were used as experiment material to investigate the adaptability to drought stressand population differences in adaptability, and the effects of shade and exogenous abscisicacid (ABA) application on the drought tolerance. Our results could provide a strongtheoretical evidence and scientific direction for the afforestation, and rehabilitation ofecosystem in the arid and semi-arid area, and provide a strong evidence for adaptivedifferentiation of different populations, and so may be used as criteria for species selectionand tree improvement. The results are as follows:1. A large set of parallel response to drought stress: Drought stress caused pronouncedinhibition of the growth and increased relatively dry matter allocation into the root. For thetwo populations, the shoot height, basal diameter and total biomass were decreased but theroot/shoot ratio and fine root/coarse root ratio were increased under drought conditions；Drought stress caused pronounced inhibition of photosynthesis, decreased the stomatalconductance, transpiration rate, and photosynthetic nitrogen-use efficiency (PNUE) butincreased the instantaneous water use efficiency. Drought significantly improved the levels ofreactive oxygen species and malondialdehyde (MDA) and to induce the entire set ofantioxidative systems including the increase of activities of superoxide dismutase (SOD),ascorbate peroxidase (APX), catalase (CAT) and ascorbate (AsA) content. Drought decreased the leaf relative water content (RWC) but improved the capability of osmotic adjustmentindicated by the higher proline accumulation. Drought also increased the ABA content andcarbon isotope composition (δ13C), which indicating the long period water use efficiency wasimproved under drought. These results demonstrate that there are a large set of parallelchanges in the morphological, physiological and biochemical responses when plants areexposed to drought stress; these changes may enhance the capability of plants to survive andgrow during drought periods.2. Difference in adaptation to drought stress between contrasting populations of P.cathayana: Compared with the Hanyuan population (wet climate), the Ledu population (dryclimate) showed higher root/shoot ratio and water use efficiency, exhibited higherantioxidative systems capability thus resulting in less oxidative damage, accumulated moreABA and free proline content under drought conditions. The results suggested that there weredifferent water-use strategies between the two populations. The Ledu population, whichcomes from dry climate region, with higher drought tolerance, may employ a conservativewater-use strategy, whereas the Hanyuan population, which comes from wet climate, withlower drought tolerance, may employ a prodigal water-use strategy. These variations indrought responses may be used as criteria for species selection and tree improvement.3. The effects of shade on the drought tolerance: The reduction in the availability of lightand water affected the morphological and physiological responses of the two P. cathayanapopulations. In addition, the light environment modified the growth responses of P.cathayana seedlings to varying water environments in different ways depending upon theintensity of the light levels considered. There is an apparent alleviation to drought effects bymoderate shade in P. cathayana seedlings, as indicated by the higher leaf RWC, and unchanged net photosynthesis and PNUE, as well as by the lower antioxditative enzymeactivity, MDA, ABA and δ13C levels, which implied moderate shade did not significantlylimited the carbon acquisition or inhibited the plant growth, but ameliorated the detrimentaleffects of drought. On the other hand, an apparent aggravation to drought effects by severeshade was also observed, as indicated by the pronounced decrease of plant growth and net photosynthesis, the lower total biomass, ABA level, δ13C, free proline content andantioxditative enzyme activity and higher MDA accumulation. By contrast, the twopopulations showed different responses to shade and drought. The Hanyuan population,which comes from a riparian basin having a relatively wet climate and less annual solarradiation, is more sensitive to drought but more tolerant to shade. The Ledu population, whichcomes from a mountainous plateau with less rainfall and with more annual solar radiation, ismore tolerant to drought but more sensitive to shade. The results demonstrated that theendurance of plants to stress is a result of long-term evolution and adaptation to theenvironment, as suggested by the different strategies employed by the P. cathayanapopulations originating from contrasting habitats when they were exposed to drought andshade.4. The effects of exogenous ABA application on the drought tolerance: For bothpopulations under drought conditions tested, exogenous ABA application significantlyimproved the root/shoot ratio, fine root/coarse root ratio, and decreased the specifical leaf area.On the physiological and biochemical traits, exogenous ABA application significantlydecreased stomatal conductance, transpiration rate and net photosythesis but increased theinstance water use efficiency and leaf RWC. On the other hand, exogenous ABA applicationsignificantly increased endogenous ABA, proline, solube sugar and AsA content, as well asSOD, APX and CAT activities, thus reduced the damage of reactive oxygen species. Moreover,the long period water use efficiency as indicated by δ13C was also improved by exogenousABA application. In additionally, there was different responsive between the two populationsto drought and exogenous ABA application. The Hanyuan population, which comes from wetclimate region, is more sensitive to drought, and the effect of exogenous ABA is moreobviously than that in the Ledu population, which comes from dry climate region and is moredrought-responsive. Therefore, we can use exogenous ABA application to improve theresistance of plants, especially for the drought- sensitive species or populations.

中国西部亚热带常绿阔叶林木本植物小枝功能生态学初步研究

常绿阔叶林以其富饶的生物资源、丰富的生物多样性和巨大的生态与环境效益引起了人们越来越大的重视，它的研究已成为国际植被科学界关注的主题之一。我国分布着世界上面积最大的亚热带常绿阔叶林，在世界植被中具有重要地位，它的分布表现出明显的地带性差异，存在着多样的植物群系及其对应的气候特征。但是在植物功能性状领域，与全球范围其它生物群系相比，常绿阔叶林物种的研究较少，其功能性状间、功能性状与环境间的关系尚不清晰。 本研究以常绿阔叶林木本植物的当年生小枝为对象，试图从小枝水平上的生物量分配格局、叶片大小与数量的权衡关系、小枝茎的构型效应、叶片元素化学计量学，以及小枝大小的成本与效益分析等方面，较为系统地揭示小枝水平上的植物功能性状间及其与气候间的关系。因此，在华西雨屏带内部的不同纬度设置峨眉－青城－雷波－平武的温度梯度进行比较，并对有降水差异的川西南偏湿性（雷波）与偏干性常绿阔叶林（西昌）进行对比研究，同时在不同山体进行不同海拔梯度的比较研究。 本文主要研究结果如下： （1）小枝生物量分配格局叶水平上，叶片重－叶柄重（Y轴vs.X轴,下同）呈斜率小于1的异速生长关系，表明叶柄对叶内部的生物量分配影响显著。小枝水平上，叶和茎的生物量以及它们与小枝总生物量间基本呈等速生长关系，表明大的小枝或大叶物种不一定在叶生物量的分配上占优势。不同生活型间，在小枝或者茎的生物量一定时，常绿物种叶片的生物量比例较落叶物种稍高。与温度和水分较优越（峨眉及其低海拔）的生境相比，在相对低湿（螺髻）与低温（平武）的生境中的植物会减少对叶的投入而增加对支撑部分的投资比例。 （2）小枝叶片大小与数量的权衡无论是不同气候带还是不同生活型以及不同海拔梯度，叶片大小与出叶强度基本都是呈负的等速生长关系，表明了叶片大小－数量在小枝水平上的权衡。在不同气候梯度的对比中，叶片数量（出叶强度）一定时，高温和高水分生境（峨眉）比低温（平武）和低湿（螺髻山）生境中的物种的叶片大小（质量和面积）更大，表明不同生境的比较中，小的叶片可能具有较高的出叶强度和更高的适合度收益。“出叶强度优势”（Leafingintensitypremium）假说可能不适宜解释不同生境物种叶片大小差异。 （3）小枝茎的构型效应虽然茎长和茎径与叶片大小都呈正相关关系，与出叶强度都呈负相关关系，但茎长/茎径比与叶/茎生物量之比呈负相关关系；与叶片的大小呈负相关关系，与出叶强度呈正相关关系。这说明小枝构型能影响小枝叶/茎生物量分配和叶大小－数量的权衡关系。其影响机制可能是小枝内部的顶端优势。另外，茎长/茎径比在低湿和低温等不利生境中的植物中较高，而在降水和温度较适宜环境中较低。 （4）叶片C、N、P化学计量学N含量和P含量，C/N比和比叶重（LMA,leafmassperarea）呈正的等速生长关系，而N和LMA，P和LMA呈负的等速生长关系。在LMA一定时，C/N比随着生境胁迫压力的增加而降低，N、P含量随着生境压力的增加而增加。在P含量一定时，N含量随着生境压力的增加而降低，即N/P比在生境条件较优（峨眉及其低海拔）时较高。常绿和落叶植物叶片的N/P比没有差异，在LMA一定时，常绿植物的N、P含量较高、C/N比较低。总之，植物的C、N、P化学计量学特征受叶片属性如LMA与气候，及其相互作用的影响。 （5）小枝大小的代价与效益分析、TLA与小枝总重总叶面积（TLA,totalleafarea，Y轴，下同）与总叶重（X轴）均呈斜率小于1的异速生长关系，TLA与小枝横切面积呈斜率为1的等速生长关系。表明叶片面积的增加总是小于叶重和小枝总重的增加，随着小枝的增大，它的叶面积支撑效率下降。在热量和降水优越的生境（峨眉及其低海拔）中，相同小枝重或者相同茎横切面积的小枝，其叶面积支撑效率较低湿与低温环境下（螺髻山、平武及高海拔）的高。 总体上，本文初步研究了小枝水平上可能存在的以下三种权衡关系：叶－茎生物量分配权衡；叶片大小－数量的权衡；小枝茎长－茎径的权衡关系，以及气候要素等对这三种权衡关系的影响。在此基础上，我们还讨论了这些权衡关系的可能形成机制，及其与物种生态适应的联系。本研究丰富了生活史对策中关于权衡关系的研究内容，为我国常绿阔叶林功能生态学研究积累了材料。 Evergreen broad-leaved forests are attracting much more attention from vegetation ecologists than ever before because of their abundant nature resource and biological diversity, and also great ecological benefits. China has the largest distribution of subtropical evergreen broad-leaved forests (temperate rainforests) that are typical and representative in the world. The forests span over more than ten degrees in latitude and more than 30 degrees in longitude, providing an ideal place to study plant functional ecology, i.e., the climatic effect on plant functional traits and the relationship between the traits. However, relative to the other biomes, there are few studies addressing functional ecology of the plant species from subtropical evergreen broad-leaved forests. In this study, I focused on the leaf size-twig size spectrum of the woody species of subtropical evergreen broad-leaved forests in southwestern china. I collected data on leaf size and number, twig size in terms of both mass and volume, and stem architecture from five temperate mountains, and then I analyzed the relationships between leaf and stem biomass and between leaf size and number, the effect of stem length/diameter ratio on biomass allocation and on the relationship between leaf size and number, leaf C:N:P stoichiometry, and the twig efficiency of supporting leaf area in relation to twig size. I also addressed the climate effect on the spectrum. The temperature gradient from warm to cool sites was represented by Emei Mountain, Qingchengshan, Leibo, and Pingwu, and the rainfall gradient was assumed to emerge from the comparison between Leibo (High) and Luojishan (Low). In addition, altitudinal effects were analyzed with comparisons between low and high altitudes for each mountains. My main results are as follows. Isometric relationships were found between leaf mass and twig mass and between lamina mass and twig mass, suggesting that the biomass allocation to leaves or laminas was independent of twig mass. Petiole mass disproportionably increase with respect to lamina mass and twig mass, indicating the importance of leaf petioles to the within-twig biomass allocation. In addition, the investigated species tended to have a larger leaf and lamina mass, but a smaller stem mass at a given twig mass at favorable environments including warm and humid sites or at low altitude than unfavorable habitats, which might be due to the large requirements in physical support and transporting safety for the species living at unfavorable conditions. Moreover, the evergreen species invested more in leaves and laminas than the deciduous at given stem or twig biomass within any specified habitats. Negative, isometric scaling relationships between leaf number and size broadly existed in the species regardless of climate, altitude, and life forms, suggesting a leaf size/number trade-off within twigs. Along the climatic gradients, at given leaf number or leafing intensity, the leaves were larger in the favorable environments than the poor habitats. This suggested that the fitness benefit gained by small leaves could be larger than that with high leafing intensity in the stressful sites. I concluded that the “leafing intensity premium” hypothesis was not appropriate to interpreting between-habitat variation in leaf size. Both stem length and diameter were positively correlated to leaf size but negatively correlated to leafing intensity. The ratio of stem length to diameter was negatively correlated to leaf mass fraction, and it was negatively correlated to leaf size but positively correlated to leafing intensity. This suggested that the stem architecture influenced twig biomass allocation and the relationship between leaf size and number. The mechanism underlying the architectural effect might lie in the apical dominance within twig. Moreover, the ratio was greater in unfavorable habitats but smaller in favorable environments. Positive, isometric relationships were found between N and P contents per leaf mass, and between C/N ratio and leaf mass per area (LMA), but N and P contents scaled negatively to LMA. C/N ratio decreased but N and P increased with increasing habitat stress at a given LMA. N content declined with increasing habitat stress at given P content. These indicated that N/P and C/N were higher but LMA was lower in favorable habitats than in the other circumstances. The evergreen and deciduous species were non-heterogeneous in N/P, but the evergreen species have higher N and P contents and lower C/N than the deciduous ones. In general, C:N:P stoichiometry were related to both climatic conditions and other important functional traits like LMA. Total leaf area (TLA) allometricly scaled to leaf mass with a slope shallower than 1, similar to the relationship between TLA and total twig mass (leaf mass plus stem mass), suggesting that TLA failed to keep pace with the increase of leaf mass and twig size. However, TLA scaled isometricly to twig cross-sectional area. Thus, it could be inferred that the twig efficiency of displaying leaf area decreased with increasing twig size. In addition, the efficiency at a given twig size was large in favorable than unfavorable habitats. In general, in this preliminary study, I studied three tradeoff relationships within twigs, i.e., between leaf and stem biomass, between leaf number and size, and between stem length and diameter, as well as the climatic effect on the relationships. I discussed the mechanisms underlying the tradeoff relationships in view of biophysics and eco-physiology of plants. I believe that this study can serve as important materials advancing plant functional ecology of subtropical forest and that it will improve the understanding of life history strategies of plants from this particular biome.

青杨(Populus cathayana Rehd.)雌雄植株对干旱胁迫的生理生态响应差异

随着全球气候变暖和温室效应加剧，干旱和荒漠化成为威胁人类生存和发展的主要 灾害，许多被子植物对干旱胁迫的生理、生态和生化响应已逐步得以报道，但很少有开 展干旱胁迫对雌雄异株植物的影响方面的研究。由于这类植物在长期进化过程中已经在 生长、性比、生殖格局、空间分布、资源配置和生物量分配等方面形成了明显的性别差 异，因此，干旱胁迫必将对其雌雄植株产生不同的生理生态影响。本研究以青杨为模式 植物，采用植物生态、生理及生物化学等研究方法，系统研究青杨雌雄植株在常温、增 温以及喷施外源脱落酸的条件下对干旱胁迫的响应，揭示其在生长形态、生物量分配、 光合作用、用水效率和生理生化等方面的性别间差异。主要研究结果如下： 1. 青杨雌雄植株对干旱胁迫的综合响应。 与较好水分条件相比，干旱胁迫显著降低了青杨雌雄植株的光合作用和生长发育， 影响了许多生理生化过程，并导致雌雄植株在生长发育、气体交换、用水效率、膜脂抗 氧化和抗氧化系统酶活性方面表现出显著的性别间差异。在较好水分条件下，雌雄植株 之间在株高、基径、生物量、净光合速率、蒸腾速率、用水效率以及丙二醛、脱落酸和 游离脯氨酸等生化物质含量方面均无显著差异。但在干旱胁迫下，雄株在生长发育、气 体交换、水分利用效率、膜脂过氧化保护和抗氧化系统酶活性方面均显著高于雌株，表 现出比雌株更高的株高、基径、叶面积、总叶片数、总生物量、总色素含量、类胡萝卜 素含量、净光合速率、蒸腾速率、羧化效率、光系统II最大光化学效率、内在水分利用 效率、碳同位素组分、过氧化氢酶和过氧化物酶活性等，而在CO2补偿点、比叶面积、 叶绿素a/b、丙二醛、脱落酸和超氧化物歧化酶活性等指标上显著低于雌株。与雌株相比， 雄株表现出更高的干旱胁迫适应能力，而雌株的生长发育和生理生化过程更易遭受干旱 胁迫的影响。 2. 干旱胁迫下的青杨雌雄植株对增温处理的综合响应 与环境温度相比，增温在干旱胁迫前后均显著促进了雌雄植株的生长发育、气体交 换，降低水分利用效率，影响生化物质含量，并促使青杨雌雄植株之间在干旱胁迫下表 现出显著的差异。在较好水分条件下，增温导致雌株的株高、基径、叶面积、总叶片数、 总生物量和超氧化物歧化酶活性显著高于雄株，而用水效率、丙二醛、脱落酸和游离脯 氨酸、抗坏血酸过氧化物酶和过氧化物酶活性低于雄株。在干旱胁迫下，增温将导致雄 株的株高、基径、叶面积、总生物量、净光合速率、蒸腾速率、气孔导度、总色素含量、 相对含水量、过氧化氢酶和抗坏血酸过氧化物酶活性等显著高于雌株，而光系统II 最大 光化学效率、内在水分利用效率、碳同位素组分、丙二醛、脱落酸、游离脯氨酸和超氧 化物歧化酶活性显著低于雌株。与雄株相比，水分较好条件下的增温有利于促进雌株的 生长发育，并在生理生态特征上优于雄株。而干旱胁迫下的增温则加剧了水分胁迫强度， 致使雌株的生长发育遭受比雄株更多的负面影响。 3. 干旱胁迫下的青杨雌雄植株对喷施外源脱落酸处理的综合响应 与对照相比，在干旱胁迫下喷施外源脱落酸可显著增加青杨雌雄植株的生长发育、 气体交换、降低水分利用效率，影响了生化物质含量，并导致青杨雌雄植株之间在干旱 胁迫下表现出显著的生理生态差异。在干旱胁迫下，喷施外源脱落酸致使雌株的株高、 叶面积、叶干重、细根干重、总生物量、净光合速率、蒸腾速率、气孔导度、光系统II 最大光化学效率、非光化学淬灭系数、相对含水量、总光合色素、类胡萝卜素、脱落酸、 超氧化物歧化酶和过氧化物酶活性的增加量显著高于雄株，而根重比、根冠比、细根/ 总根、比叶面积、内在水分利用效率、碳同位素组分、丙二醛、脯氨酸、过氧化氢酶和 抗坏血酸过氧化物酶活性等指标的减少量上显著低于雄株。与对照相比，干旱胁迫下的 喷施外源脱落酸则一定程度能减缓植株遭受胁迫的压力，促进植株生长和气体交换，减 少了植株体内的过剩自由基数量，并促使雌株的生长发育和光合能力显著提高，增强其 抗干旱胁迫能力。 With development of global warming and greenhouse effect, drought and desertification have been became main natural disasteres in resent years. Studies on ecophysiological responses of most angiosperm species to environmental stress have been reported, but little is known about dioecious plant responses to drought stress. Since significant differences on growth, survival, reproductive patterns, spatial distribution, as well as resource allocation between males and females of dioecious plant have been formed during evolutionary process, sexual different ecophysiological responses should be caused by drought stress. In this experiment, Populus cathayana Rehd. was used as model plant to study the sex-related responses to drought by using the ecological, physiological and biochemical methods under normal atmospheric temperature, elevated temperatures and exogenous abscisic acid (ABA) application treatment respectively, and to expose the sexual differences in growth, biomass allocation, photosynthesis, water use efficiency and some biochemical material contents in the males and females of dioecious plant. The results are follows: 1. A large set of parallel responses of males and females of P. cathayana to drought stress Compared with well-watered treatment, drought significantly decreased growth and photosynthesis of P. cathayana individuals, affected some physiological and biochemical processes, and induced males and females to exhibit obvious sexual differences in growth, gas exchange, water use efficiency, lipid peroxidation protection and antioxidant defenses enzyme system. Under well-watered treatment, there were no significant sexual differences in height growth (HG), basal diameter (BD), dry matter accumulation (DMA), net photosynthesis rate (A), transpiration (E), water use efficiency (WUE), and malondialdehyde (MDA), abscisic acid (ABA) and praline (Pro). However, under drought stress, males were found to exhibit higher HG, BD, leaf area (LA), total leaf number (TLA), DMA, total chlorophyll contents (TC), carotenoids content (Caro), A, E, carboxylation efficiency (CE), the maximum efficiency of PSII (Fv/Fm), intrinsic water use efficiency (WUE ), carbon isotope composition (δ13C), catalase (CAT), peroxidase (POD) and lower CO2 compensation point (Γ), specific leaf area (SLA), chlorophyll a/b ratio (Chla/Chlb), MDA, ABA and superoxide dismutase (SOD) than females. The results suggest that males possess greater drought resistance than do females and females suffer more negative effect on growth and development, physiological and biochemical processes than males under drought stress. 2. A large set of parallel responses of drought-stressed males and females of P. cathayana to elevated temperatures Compared with environmental temperature, elevated temperature treatment significant increased growth and gas exchange, decreased water use efficiency, changed some biochemical material contents of P. cathayana individuals, and induced males and females to exhibit obvious differences under drought stress. Under good water condition, elevated temperature treatment caused females to show significant higher HG, BD, LA, TLN, DMA, SOD activity, and great lower WUE, MDA, ABA, Pro, ascorbate peroxidase (APX) and POD than do males. On contrary, under drought condition, elevated temperature treatment induced males to exhibit higher HG, BD, LA, DMA, A, E, stomatal conductance (gs), relative water content (RWC), CAT, APX activity but lower Fv/Fm, WUE, δ13C, MDA, ABA, Pro, SOD activity than do females. The results suggest that females will benefit from elevating temperature under good water condition by possessing better ecophysiological processes than that of males, but will suffer from greater negative effects than do males when grown under drought stress with elevated temperature treatment. 3. A large set of parallel responses of drought-stressed males and females of P. cathayana to exogenous ABA application Compared with controls, exogenous ABA application under drought greatly increased growth and gas exchange, decreased water use efficiency, changed some biochemical material contents in P. cathayana individuals, and induced males and females to exhibit obvious sexual differences under drought. Under drought stress, exogenous ABA application induced females to exhibit more increases in HG, LA, leaf weight (LW), fine root weight (FRW), DMA, A, E, g, Fv/Fm, non-photochemical quenching coefficient (qN), RWC, TC, Caro, ABA, SOD, POD s activity than males, but to show lower decreases in root/weight ratio (RWR), root mass/foliage area ratio (RF), fine root/total root ratio (FT), SLA, WUE, δ13C, MDA, Pro, CAT, APX than males. The results suggest that exogenous ABA application under drought stress will eliminate negative damages caused by drought stress at a certain extent，promote the growth and gas exchange of plant and decrease the number of superfluous 1O2 in plant cells of males and females of P. cathayana. Furthermore, exogenous ABA application promoted more drought resistance in females than in males by increasing more growth and photosynthetic capacity in females under drought stress.

干旱胁迫与施N条件下白刺花（Sophora davidii）幼苗生长及其适应机制

干旱环境常常由于多变的降水事件和贫瘠土壤的综合作用，表现出较低的生产力和较低的植被覆盖度。全球性的气候变暖和人类干扰必将使得干旱地区缺水现状越来越严竣。贫瘠土壤环境中已经很低的有效养分含量也将会随着干旱的扩大而越来越低。干旱与半干旱系统中不断加剧的水分与养分的缺失将严重限制植物的生长和植被的更新，必然会使得已经恶化的环境恶化速率的加快、恶化范围的加大。如何抑制这种趋势，逐步改善已经恶化的环境是现在和将来干旱系统管理者面临的主要关键问题。了解干旱系统本土植物对未来气候变化的适应机制，不仅是植物生态学研究的重要内容，也对人为调节干旱环境，改善干旱系统植被条件，提高植被覆盖度具有重要的实践意义。 本研究以干旱河谷优势灌木白刺花（Sophora davidii）为研究对象，通过两年大棚水分和施N控制实验和一个生长季野外施N半控制实验，从植物生长－生理－资源利用以及植物生长土壤环境特征入手，系统的研究了白刺花幼苗生长特性对干旱胁迫和施N的响应与适应机制，并试图探讨施N是否可调节干旱系统土壤环境，人工促进干旱条件下幼苗定居，最终贡献于促进植被更新实践。初步研究结论如下： 1）白刺花幼苗生长、生物量积累与分配以及水分利用效率对干旱胁迫和施N处理的适应白刺花幼苗株高、基径、叶片数目、叶面积、根长、生物量生产、相对含水量和水分利用效率随着干旱胁迫程度的增加而明显降低，但地下部分生物量比例和R/S随着干旱胁迫程度的增加而增加。轻度施N处理下幼苗株高、基径、叶片数目、叶片面积和生物量生产有所增加。但重度施N处理下这些生长指标表现出微弱甚至降低的趋势。严重干旱胁迫条件下，幼苗叶面积率、R/S、相对含水量和水分利用效率也以轻度施N处理为最高。 2）白刺花幼苗叶片光合生理特征对干旱胁迫和施N处理的适应叶片光合色素含量和叶片光合效率随着干旱胁迫程度的增加而显著降低，并且PS2系统在干旱胁迫条件下表现出一定程度的光损害。但是比叶面积随着干旱胁迫程度的增加而增加。在相对较好水分条件下幼苗净光合速率的降低可能是因为气孔限制作用，而严重干旱胁迫条件下非气孔限制可能是导致幼苗叶片光合速率下降的主要原因。叶片叶绿素含量、潜在光合能力、羧化效率、光合效率以及RUBP再生能力等在施N处理下得到提高，并因而改善干旱胁迫条件下光合能力和效率。虽然各荧光参数对施N处理并无显著的反应，但是干旱胁迫条件下qN和Fv/Fm在轻度施N处理下维持相对较高的水平，而两年连续处理后在严重干旱胁迫条件下幼苗叶片光合效率受到重度施N处理的抑制，并且Fv/Fm和qN也在重度施N处理下降低。 3）白刺花幼苗C、N和P积累以及N、P利用效率对干旱胁迫和施N处理的适应白刺花幼苗C、N和P的积累，P利用效率以及N和P吸收效率随干旱胁迫程度的增加而显著降低，C、N和P的分配格局也随之改变。在相同水分处理下，C、N和P的积累量、P利用效率以及N和P吸收效率在轻度施N处理下表现为较高的水平。然而，C、N和P的积累量和P利用效率在重度施N处理下不仅没有表现出显著的正效应，而且有降低的趋势。另外，在相同水分条件下白刺花幼苗N利用效率随着施N强度的增加而降低。 4）白刺花幼苗生长土壤化学与微生物特性对干旱胁迫和施N的适应白刺花幼苗生长土壤有机C、有效N和P含量也随干旱胁迫程度的增加而明显降低。干旱胁迫条件下土壤C/N、C/P、转化酶、脲酶和碱性磷酸酶活性的降低可能表明较低的N和P矿化速率。尽管微生物生物量C、N和P对一个生长季干旱胁迫处理无显著反应，但微生物生物量C和N在两年连续干旱胁迫后显著降低。土壤有机C和有效P含量在轻度施N处理下大于重度施N处理，但是有效N含量随着施N强度的增加而增加。微生物生物量C和N、碱性磷酸酶和转化酶活性也在轻度施N处理下有所增加。但是碱性磷酸酶活性在重度施N处理下降低。 5）野外条件下白刺花幼苗生长特征及生长土壤生化特性对施N的适应植物生长、生物生产量、C的固定、N、P等资源的吸收和积累、其它受限资源的利用效率（如P）在轻度施N处理下均有所增加，但N利用效率有所降低。幼苗生物生产量及C、N和P等资源的分配格局在轻度施N处理下也没有明显的改变。白刺花幼苗叶片数目、生物生产量和C、N、P的积累量在重度施N处理下虽然也相对于对照有所增加，但幼苗根系长度显著降低。生物量及资源（生物量、C、N、P）在重度施N处理下较多地分配给地上部分（主要是叶片）。另外，土壤有机C、全N和有效N含量随外源施N的增加而显著增加，土壤pH随之降低，但土壤全P含量并无显著反应。其中有机C含量和有效P含量以轻度施N处理最高。微生物生物量C、N和P在轻度施N处理下也显著增加，而微生物生物量C在重度施N处理下显著降低。同时，转化酶、脲酶、碱性磷酸酶和中性磷酸酶活性在施N处理下也明显的提高，但酸性磷酸酶和过氧化氢酶活性显著降低，其中碱性磷酸酶和中性磷酸酶活性以轻度施N处理最高。 综合分析表明，干旱河谷水分和N严重限制了白刺花幼苗的生长。施N不能完全改变干旱胁迫对白刺花幼苗的抑制的作用，但是由于施N增加土壤N有效性，改善土壤一系列生物与化学过程，幼苗的生长特性也对施N表现出强烈的反应，表现为植物结构与资源分配格局的改善，植物叶片光合能力与效率的提高，植物生长以及利用其他受限资源（如水分和P）的效率的增加，致使植物自身生长及其生长环境在干旱环境下得到改善。但是过度施N不仅不能起到改善干旱胁迫下植物生长环境、促进植物生长的作用，反而在土壤过程以及植物生长过程中加重干旱胁迫对植物的伤害。因此，建议在采用白刺花作为先锋种改善干旱河谷系统环境的实践中，可适当施加N以改善土壤环境，调节植物利用与分配资源的效率，促进植物定居，得到人工促进种群更新的目的。但在实践过程中也要避免过度施N。 Arid regions of the world are generally noted for their low primary productivity which is due to a combination of low, unpredictable water supply and low soil nutrient concentrations. The most serious effects of global climate change and human disturbances may well be those which related to increasing drought since drought stress has already been the principal constraint in plant growth. The decline in total rainfall and/or soil water availability expected for the next decades may turn out to be even more drastic under future warmer conditions. Nevertheless, water deficit is not the only limiting factor in arid and semiarid environments. Soils often suffer from nutrient (especially N and P) deficiencies in these ecosystems, which can also be worsened by climate change. How to improve the poor soil quality and enhance the vegetation coverage is always the problem facing ecosystem managers. The adaptive mechanisms of native plant to future climate change is always the focus in plant ecology, it also plays important roles in improving vegetation coverage by manual controlled programmes. Sophora davidii is a native perennial shrub of arid valleys, which is often predominant on eroded slopes and plays a vital role in retaining ecological stability in this region. It has been found that S. davidii was better adapted to dry environment than other shrubs, prompting its use for re-vegetation of arid lands. A two-years greenhouse experiment and a field experiment were conducted in order to understand the adaptation responses of Sophora davidii seedlings to different water and N conditions, and further explore if additional N supply as a modified role could enhance the adaptation ability of S. davidii seedlings to dry and infertile environment. Two-month old seedlings were subjected to a completely randome design with three water (80%, 40% and 20% water field capacity (FC)) and three N supply (N0: 0, Nl: 92 and Nh: 184 mg N kg-1 soil) regimes. Field experiment was arranged only by three N supplies in the dry valley. 1) The growth, biomass partitioning and water-use efficiency of Sophora davidii seedlings in respond to drought stress and N supply Seedlings height, basal diameter, leaf number, leaf area, root length, biomass production, relative water content (RWC) and WUE were decreased with increase of drought stress. An increase in below-ground biomass was observed indicating a higher root/shoot ratio (R/S) under drought stress conditions. Low N supply increased seedlings height, basal diameter, leaf number, leaf area, and biomass production, but decreased root length. In contrast, these growth characteristics showed little or negative effect to high N supply treatment. Leaf percentages increased with increase of N supply, but fine root percentages decreased. In addition, Low N supply rather than the other two N treatments increased leaf area ratio (LAR), leaf/fine root mass ratio (L/FR), R/S and RWC under severe drought stress (20%FC), even though these parameters could increase with the high N supply treatment under well-watered condition (80%FC). Moreover, Low N supply also increased WUE under three water conditions, but high N supply had little effect on WUE under drought stress conditions (40%FC and 20%FC). 2) Leaf gas exchange and fluorescence parameters of Sophora davidii seedlings in respond to drought stress and N supply Leaf area (LA), photosynthetic pigment contents, and photosynthetic efficiency were decreased with increase of drought stress, but specific leaf area (SLA) increased. Photodamage in photosystem 2 (PS2) was also observed under drought stress condition. The decreased net photosynthetic rate (PN) under relative well-watered water conditions might result from stomatal limitations, but the decreased PN under other hand, photosynthetic capacity by increasing LA, photosynthetic chlorophyll contents, Pnmax, CE, Jmax were increased with increase N supply, and photosynthetic efficiency was improved with N supply treatment under water deficit. Although N supply did a little in alleviating photodamages to PS2 caused by drought stress, low N supply enhanced qN and kept relative high Fv/Fm under drought stress condition. However, high N supply inhibited leaf photosynthetic efficiency, and declined Fv/Fm and qN under severe drought stress condition after two year continues drought stress and N supply. 3) Carbon accumulation, nitrogen and phosphorus use efficiency of Sophora davidii seedlings in respond to drought stress and N supply C, N and P accumulation, NUE , N and P uptake efficiency (NUtE and NUtE ) P N P were decreased with increase of drought stress regardless of N supply. On the other hand, the S. davidii seedlings exhibited strong responses to N supply, but the responses were inconsistent with the various N supply levels. Low N supply rather than the other two N treatments increased C, N and P accumulation, improved NUEP, NUtE and NUtE under corresponding water condition. In contrast, high N supply N P did few even depressed effects on C, N and P accumulation, and NUEP, although NUtEN and NUtEP could increase with high N supply under corresponding water conditions. Even so, a decrease of NUEN was observed with increase of N supply under corresponding water conditions. 4) Soil microbial and chemical characters in respond to drought stress and N supply The content of soil organic C, available N and P were decreased with increase of drought stress. Decreases in C/N and C/P, and invertase, urea and alkaline phosphatase activity were also observed under drought stress conditions, indicating a lower N and P mineralization rate. Although microbial biomass C, N and P showed slight responses to drought stress after one growth period treatment, microbial biomass C and N were also decreased with increase of drought stress after two year continuous treatment. The content of soil organic C and available P showed the stronger positive responses to low N supply than which to high N supply, although than the other two N treatments increased microbial biomass N and invertase activity under severe drought stress condition, even though invertase activity could increase with high N supply treatment under relative well-water conditions. Moreover, low N supply treatment also increased C/P and alkaline phosphatase activity which might result from higher P mineralization, but high N supply did negative effects on alkaline phosphatase activity. 5) The growth characteristics of Sophora davidii seedlings and soil microbial and chemical characters in respond to N supply under field condition Low N supply facilitated seedlings growth by increasing leaf number, basal diameter, root length, biomass production, C, N and P accumulation and absorption, and enhancing the use efficiency of other limited resources as P. Compared to control, however, low N supply did little effect on altering biomass, C, N and P portioning in seedlings components. On the contrary, high N supply treatment also increased leaf number, biomass and C, N and P accumulation relative to control, but significantly decreased root length, and altered more biomass and resources to above-ground, which strongly reduced the ability of absorbing water under drought condition, and thus which might deep the drought stress. In addition, N supply increased soil C, N and available N content, but declined pH and showed little effects on P content. Low N supply showed higher values of soil C and available P content. Low N supply also increased microbial biomass C, N and P, although high N supply decreased microbial biomass C. N supply significantly enhanced soil invertase, urea, alkaline and neutral phosphratase activity, while declined acid phosphratase and catalase activity. Low N supply exhibited higher alkaline and neutral phosphratase activity compared to the others. The results from this study indicated that both drought and N limited the growth of S. davidii seedlings and their biomass production. Regardless of N supply levels, drought stress dramatically reduced the seedlings growth and biomass production. Although plant growth parameters, including basal diameter, height, leaf number, and biomass and their components were observed to be positive responses to low N supply, N supply alone can not alter the diminishing tendency which is caused by drought. available N content increased with increase N supply. In addition, low N supply rather These findings imply that drought played a primary limitation role and N was only the secondary. Even so, appropriate N supply was seemed to enhance the ability that S. davidii seedlings adapted to the xeric and infertile environment by improving soil processes, stimulating plant growth, increasing recourses accumulation, enhancing use efficiency of other limited resources, and balancing biomass and resources partitioning. Appropriate N supply, therefore, would be recommended to improve S. davidii seedling establishment in this region, but excess N supply should be avoided.

生姜化感作用机理及其栽培模式研究

近年来，随着对作物重茬（连年种植）障碍原因的深入研究，植物的化感作用越来越受到国内外众多学者的重视。而作为重要调料和药用植物的生姜，其连作障碍也备受关注，系统地研究生姜化感作用将有助于理解和最终解决生姜连作障碍问题。本文通过研究生姜不同部位、不同浓度的水浸液对与其间作的两个物种（大豆和四季葱）种子的萌发及幼苗生长的影响，从而证明生姜化感作用的存在；并通过温室盆栽实验研究了生姜的自毒作用（即研究生姜不同部位、不同浓度的水浸液对其幼苗的形态、生理生化、光合作用、土壤酶、土壤微生物多样性及土壤养分的影响），从而揭示生姜退化和衰老的机制，并为生姜筛选出合适的间作物种提供科学依据，对生姜连作障碍提出科学的解决方法。主要研究结果如下： 1. 与对照相比，生姜所有部位（根茎、茎、叶）、所有浓度（10、20、40、 80 g l-1）的水浸液均抑制了大豆种子和葱籽的萌发率、幼苗生长、水分吸收和脂肪酶活性，并且其抑制程度随着水浸液浓度的增加而增强，其生姜各部位水浸液抑制效应的强弱顺序为茎＞叶＞根茎。这一结果表明生姜根茎、茎、叶含有能够抑制大豆种子和葱籽种子萌发和幼苗生长的水溶性化感物质。根茎是生姜的主要收获部位，而生姜的残株（主要是茎和叶）应该从大田中处理掉以减轻其抑制效应。生姜水浸液中主要化感成分包括：根茎水浸液中主要是丁香酸和伞花内脂；茎水浸液中主要是阿魏酸，且其含量最高为73.4 ug/g；叶水浸液中除了阿魏酸，其他六种物质均检测出来，但含量较高的主要有丁香酸、伞花内脂和香豆酸。 2. 生姜茎和叶不同浓度的水浸液均显著抑制了生姜幼苗的株高、每株叶片数和叶面积，其抑制程度随着水浸液浓度的增加而有所增强，而生姜幼苗每株分枝数差异不显著；同时生姜水浸液也极大程度地影响了生姜幼苗的生物量（包括地下生物量、地上生物量和总生物量，均为鲜重）。在同一浓度下，茎水浸液对生姜幼苗形态指标及生物量指标均显示出最强的抑制作用，叶水浸液次之，根茎水浸液最弱。与对照相比，低浓度的生姜根茎水浸液提高了生姜幼苗叶片内四种抗氧化酶（SOD、POD、CAT、APX）活性，高浓度的根茎水浸液抑制了四种抗氧化酶活性，而茎和叶水浸液均随着浓度的增加而抑制了四种抗氧化酶活性，三种水浸液均随着浓度的增加降低了生姜幼苗叶片内叶绿素的含量，而增加了生姜幼苗叶片的相对电导率和丙二醛含量。同时，三种水浸液均随着浓度的增加降低了生姜幼苗的光合参数（包括胞间CO2浓度、气孔导度、蒸腾速率及净光合速率）。 3. 三种生姜水浸液对所测六种土壤酶活性均产生了不同程度的影响，其中影响最大的是酸性磷酸酶和蔗糖酶，在10 g l-1 时就达到了显著水平，并且所有酶均有随着水浸液浓度增加而增大的趋势；相同部位的水浸液随着浓度的增加，细菌和真菌的数量呈增加趋势，而放线菌的数量呈减少趋势；三种生姜水浸液均随着浓度的增加降低了土壤中有机质的含量，加剧了土壤中硝态氮含量的积累，根茎水浸液对土壤有效磷、速效钾和铵态氮均显示出低浓度提高其含量而高浓度降低其含量的趋势，而茎和叶水浸液则随着浓度的增加均降低了其含量。 4. 与生姜单作相比，所有间作系统均在旺盛生长期和收获期不同程度地提高了土壤酶活性，同时也增加了土壤细菌数量及土壤微生物总数但不显著；所有间作系统在旺盛生长期和收获期均不同程度地影响了土壤真菌及放线菌数量（增加或减少），所有间作系统间的多样性指数差异不显著，除了旺盛生长期四种作物（生姜-大豆-四季葱-大蒜）的间作模式显著降低了多样性指数，其值仅为生姜单作的33.18%；生姜与大豆间作不仅提高了19.6%的生姜产量而且获得了较好的经济效益，并且，所有间作系统均显著抑制了生姜姜瘟病的发生。 5. 不同栽培模式不同程度地影响了收获期生姜的株高、分枝数、根茎产量及内在品质。其中处理2显著地促进了生姜的分枝（10.5%），同时处理2、3和4也促进了生姜的生长（株高分别增加了15.0%、11.4%和14.0%），并且这三个处理提高了生姜的产量；处理2和3能有效提高生姜块茎中维生素C（分别较单作生姜显著提高了3.29%和4.05%）、处理3显著提高了可溶性糖（8.2%）、姜辣素（4.6%）和蛋白质等有益物质的含量，降低硝酸盐有害物质的含量（处理2显著降低了14.0%），改善了姜块的外观和内在品质。并且，生姜与大豆间作具有最高的纯收入和产投比，分别较生姜单作提高了24.80%和8.8%。Recently, allelopathy has been more and more paid attentions by national and foreign scholars with profound research on reasons of crop replanted (continuous planted) obstacle. Ginger rhizome is valuable all over the world either as a spice or herbal medicine and ginger replanted obstacle is also paid attentions. Systematic research on ginger allelopathy will contribute to understanding and ultimate solving problem of ginger replanted obstacle. The effects of ginger aqueous extracts with different parts and concentrations on seed germination and early seedling growth of soybean and chive were studied in this article to testify that ginger existed allelopathy. Furthermore, ginger autotoxicity was also studied by pot experiment in greenhouse (namely research on effects of ginger aqueous extracts with different parts and concentrations on morphological indexes, physiological and biochemical indexes, photosynthesis, soil enzymes, soil microbial diversity and soil nutrients) to reveal mechanism of ginger degeneration and senescence, provide scientific basis for selecting appropriate intercropping species and put forward scientific resolvent for ginger replanted obstacle. The main results were as follows: 1. All aqueous extracts at all concentrations inhibited seed germination, seedling growth, water uptake and lipase activity of soybean and chive compared with the control, and the degree of inhibition increased with the incremental extracts concentration. The degree of toxicity of different ginger plant parts can be classified in order of decreasing inhibition as stem＞leaf＞rhizome. The results of this study suggested that rhizome, stem and leaf of ginger contained water soluble allelochemicals which could inhibit seed germination and seedling growth of soybean and chive. The rhizome is the main harvested part of ginger. The residue (mainly stems and leaves) of the ginger plant should be removed from the field so as to diminish its inhibitory effect. The main allelopathic components of three kind of aqueous extracts were as follows: Rhizome extract chiefly contained syringic acid and vmbelliferone and stem extract mainly contained frulic acid whose content was the highest (73.4 ug/g). The other six substances were detected except of frulic acid, but only contents of syringic acid, vmbelliferone and p-coumaric acid were higher. 2. Stem and leaf aqueous extracts of ginger with different concentrations significantly inhibited plant height, leaf numbers per plant and leaf area, and the degree of inhibition increased with the incremental extracts concentration. However, tiller number per plant of ginger seedling showed no significant difference. At the same time, ginger aqueous extracts also influenced biomass including under-ground biomass, above-ground biomass and total biomass (fresh weight) to a large extent. Under the same concentration, stem aqueous extract showed the mostly inhibitory effect on morphological indexes and biomass indexes of ginger seedling. Rhizome aqueous extract showed the leastly inhibitory effect and leaf aqueous extract was intervenient. Enhanced concentration of ginger aqueous extracts significantly reduced total chlorophyll content, accompanying with increases in memberane permeability (REL) and lipid peroxidation (MDA). Compared with the control, rhizome ginger aqueous extract of lower concentration (10 g l-1) increased the activities of major antioxidant enzymes (superoxide dismutase, SOD; peroxidase, POD; catalase, CAT; ascorbate peroxidase, APX) of ginger leaf tissue and higher concentration inhibited the activities of four antioxidant enzymes. However, stem and leaf aqueous extract inhibited the activities of four antioxidant enzymes with increase in concentration. Meanwhile, enhanced concentration of ginger aqueous extracts significantly reduced photo-parameters of ginger seedling (including CO2 concentration, stoma conductivity, net photosynthesis rate and transpiration rate). 3. Rhizome, stem and leaf ginger aqueous extract showed different effect on six soil enzyme activities, and acid phosphatase and invertase showed significant effect when aqueous extract concentration got 10 g l-1. Furthermore, six soil enzyme activities increased with increase in aqueous extract concentration. Bcterial and fungi number tended to increase while antinomyces tented to decrease with the increase in aqueous extract concentration of identical part. Ginger aqueous extracts reduced soil organic matter content with increased concentration, accompanying with NO3-—N accumulation in soil. Rhizome aqueous extract showed the same tendency for available P, available K and NH4+—N, namely lower concentration increased their contents in soil and higher concentration reduced their contents. While stem and leaf aqueous extracts reduced their contents with the increamental concentration. 4. All intercropping systems increased soil enzyme activities to different extent both at VGS and at HS compared to solo ginger. All intercropping systems increased the colony numbers of soil bacteria and total of soil microbe but not significantly either at VGS or at HS. All intercropping systems increased the colony numbers of soil fungi and actinomytes to a different extent (increase or decrease) both at VGS and at HS. For DI, difference between all cultivation patterns and S-G was not significant either at VGS or at HS except that G-S-C-G whose value was only 33.18% of S-G at VGS significantly decreased. G-S not only increased ginger yield by 19.6% but also obtained better economic benefit. Furthermore, all intercropping systems significantly inhibited occurrence of bacterial wilt of ginger. 5. Different cultivated pattern influenced plant height, tiller numbers, rhizome yields and intrinsic quality of ginger. Treatment 2 significantly facilitated tiller occurring (10.5%). Treatment 2, 3 and 4 promoted ginger growth (plant height respectively increased 15.0%、11.4% and 14.0%) and enhanced rhizome yields. Treatment 2 and 3 effectively increased vitamin C content (significantly increased 3.29% and 4.05% compared to solo ginger). Treatment 3 significantly increased contents of beneficial substances such as soluble sugar (8.2%), gingerols (4.6%) and protein. Treatment 2 significantly decreased contents of deleterious substance namely nitrate (14.0%) and improved appearance and intrinsic quality of ginger rhizome. Furthermore, treatment 2 (ginger/soybean intercropping) could obtain better economic benefit and showed the highest net income and ratio of benefit and cost whose values respectively increased by 24.80% and 8.8% compared to solo ginger.

增强UV-B辐射对粗枝云杉(Picea asperata Mast.)和青杨(Populus cathayana Rehd.)的影响

光是植物赖以生存的重要环境因子，但是植物在获得光的同时不可避免的会受到紫外辐射的伤害。尤其是近年来，人类向大气中排放的大量氮氧化合物和氟氯烃类化合物(CFC’s)引起臭氧分子的分解，导致到达地球表面的紫外辐射增加，特别是UV-B辐射增强。而另一方面，植物对UV-B辐射反应的敏感性在种间和品种间存在差异，主要受植物基因型，生态型和生活型的控制。本项目分别以粗枝云杉和青杨组杨树为模式植物，从形态和生理生化方面分别研究了来自不同水分背景下的粗枝云杉种群和来自不同UV-B背景下的青杨种群在增强UV-B下的反应及其反应差异,并探讨了干旱、喷施外源脱落酸(ABA)对它们抗UV-B能力的影响。研究成果可为生态系统的恢复与重建提供理论依据和科学指导。主要研究结果如下： 1. 粗枝云杉的两个种群，湿润种群(来自四川黑水)和干旱种群(来自甘肃迭部)在水分良好和干旱状况下表现出对增强UV-B的不同响应。同时，干旱对粗枝云杉抗UV-B能力的影响也得到研究：两种胁迫共同作用时，干旱表现出在一定程度上减弱了增强UV-B对粗枝云杉的生理特性的影响。 干旱胁迫显著降低了两个粗枝云杉种群的光合同化速率(A), 气孔导度(gs)和PSII的有效光量子产量(Y), 同时，提高了非光化学猝灭效率(qN)和超氧化物歧化酶(SOD)的活性。与湿润种群相比，干旱种群抗旱性更强，表现为干旱种群拥有更高的SOD和干旱进一步加剧了UV-B的胁迫效应。 本研究中，干旱胁迫单独作用时，显著降低了青杨两个种群的生物量积累和气体交换，具体包括A、gs、蒸腾速率(E)和光合氮利用效率(PNUE)，提高了两个种群的瞬时水分利用效率(WUEi)、长期水分利用效率(WUET)、碳同位素组分(δ13C)和氮含量(N)。同时，UV吸收物质和ABA含量也得到积累。另一方面，增强UV-B对青杨两个种群各个指标的影响，同干旱所引起的效应有着相似的趋势。同低海拔种群相比，高海拔种群有着更强的抗旱和抗UV-B能力，具体表现在高海拔种群有着更多的生物量积累，更强的气体交换和水分利用效率及更高水平的ABA和UV吸收物质含量。相比干旱诱导的生物量积累和气体交换的降低，在干旱和增强UV-B两个胁迫同时作用于青杨时，这种降低表现的更为明显。显著的干旱和UV-B的交互作用还表现在WUEi, WUET, δ13C, 可溶性蛋白含量, UV吸收物质含量, ABA, 叶片和茎中的N含量以及C/N比中。 3. 经过一个生长季的试验观察，增强UV-B、外源ABA及两因子共同作用对青杨的生物量积累、气体交换、内源ABA和UV吸收物质含量、抗氧化系统以及碳、氮含量和碳/氮比均产生显著影响。本试验中，青杨的两个种群分别来自中国西南部的不同海拔地区，高海拔种群来自青海大通而低海拔种群来自四川九寨。外源ABA的胁迫为直接喷施ABA到青杨叶片，而增强UV-B胁迫是利用平方波系统分别保证青杨苗暴露于外界UV-B强度和两倍于外界UV-B强度下。 研究结果显示，增强UV-B显著的降低了两个青杨种群的株高、基茎、总叶面积和总生物量等生长指标，同时也导致其A、gs、E和叶片中碳含量的减少。而显著增加了SOD和过氧化物酶(GPx)活性水平，诱导了过氧化氢(H2O2)和MDA的显著增加，促进了UV吸收物质和不同器官中内源ABA含量的显著积累。另一方面，外源ABA引起了青杨光合同化速率的下降，SOD和GPx酶活性的增强，H2O2 和 MDA含量也表现出显著增加，同时，内源ABA含量得到显著累积。同低海拔种群相比，高海拔种群具有更加抗UV-B和外源ABA的特性。显著的UV-B和ABA的交互作用表现在A, E, SOD和GPx活性，以及叶片和根部的内源ABA等一系列指标中。在所有胁迫下，叶片中的碳和氮含量同其在茎和根中的含量显著相关，另外，叶片和茎中的氮含量同茎中的碳含量显著相关。 Sunlight is an indispensable environment factor for plants survival and development. Meanwhile, photosynthetic organisms need sunlight and are thus, inevitably, exposed to UV radiation. Especially for recent years, ultraviolet radiation, especially UV-B reaching the Earth’s surface increased because of depletion of ozone layer resulted from emission of NxO and CFC’s from human activities. On the other hand, the sensitivity of plants to UV-B radiation depends on the species, developmental stage and experimental conditions. In this experiment, two populations of Picea asperata Mast from different water background and two populations of Populus cathayana Rehder from different altitude background were selected as model plants to assess the effects of enhanced UV-B radiation. Morphological and physiological traits induced by enhanced UV-B in each plant species were observed and the different responses were discussed, furthermore the influences of drought and exogenous ABA on responses induced by enhanced UV-B were studied. The study could provide a strong theoretical evidence and scientific direction for the afforestation and rehabilitation of ecosystem. The results are as follows: 1. Different responses of two contrasting Picea asperata Mast. populations to enhanced ultraviolet-B (UV-B) radiation under well-watered and drought conditions were investigated. And the effects of enhanced UV-B on tolerance of drought were also observed in our study that the UV-B exposure may have alleviated some of the damage induced by drought. Two contrasting populations, originating from a wet and dry climate region in China, respectively, were employed in our study. Drought significantly decreased CO2 assimilation rate (A), stomatal conductance (gs) and effective PSII quantum yield (Y), while it significantly increased non-photochemical quenching (qN) and the activity of superoxide dismutase (SOD) in both populations. Compared with the wet climate population, the dry climate population was more acclimated to drought stress and showed much higher activities of SOD and ascorbate peroxidase (APX), and much lower levels of malondialdehyde (MDA) and electrolyte leakage. On the other hand, enhanced UV-B radiation also induced a significant decrease in the chlorophyll (Chl) content in both populations under well-watered conditions, and a significant increase in UV-absorbing compounds in the wet climate population. After one growing season of exposure to different UV-B levels and watering regimes, the increases in MDA and electrolyte leakage, as induced by drought, were less pronounced under the combination of UV-B and drought. In addition, an additive effect of drought and UV-B on A and gs was observed in the wet climate population, and on the activity of APX and qN in the dry climate population. 2. The significant effects of drought, enhanced UV-B radiation and their combination on Populus cathayana Rehd. growth and physiological traits were investigated in two populations, originating from high and low altitudes in south-west China. Our results showed that UV-B acts as an important signal allowing P. cathayana seedlings to respond to drought and that the combination of drought and UV-B may cause synergistically detrimental effects on plant growth in both populations. In both populations, drought significantly decreased biomass accumulation and gas exchange parameters, including A, gs, E and photosynthetic nitrogen use efficiency (PNUE). However, instantaneous water use efficiency (WUEi), transpiration efficiency (WUET), carbon isotope composition (δ13C) and nitrogen (N) content, as well as the accumulation of soluble protein, UV-absorbing compounds and abscisic acid (ABA) were significantly increased by drought. On the other hand, cuttings from both populations, when kept under enhanced UV-B radiation conditions, showed very similar changes in all above-mentioned parameters, as induced by drought. Compared with the low altitude population, the high altitude population was more tolerant to drought and enhanced UV-B, as indicated by the higher level of biomass accumulation, gas exchange, water-use efficiency, ABA concentration and UV-absorbing compounds. After one growing season of exposure to different UV-B levels and watering regimes, the decrease in biomass accumulation and gas exchange, induced by drought, was more pronounced under the combination of UV-B and drought. Significant interactions between drought and UV-B were observed in WUEi, WUET, δ13C, soluble protein, UV-absorbing compounds, ABA and in the leaf and stem N, as well as in the leaf and stem C/N ratio. 3. During one growing season, significant effects induced by enhanced UV-B radiation, exogenous ABA and their combination on biomass accumulation, gas exchange, endogenous ABA and UV-absorbing compounds concentrations, antioxidant system as well as carbon (C) content, nitrogen (N) content and C/N ratio were investigated in two contrasting Populus cathayana populations, originating from high and low altitudes in south-west China. Exogenous ABA was sprayed to the leaves and enhanced UV-B treatment was using a square-wave system to make the seedlings under ambient (1×) or twice ambient (2×) doses of biologically effective UV-B radiation (UV-BBE). Enhanced UV-B radiation significantly decreased height, basal diameter, total leaf area, total biomass, A, gs, E and carbon (C) content in leaves, and significantly increased activities of SOD and guaiacol peroxidase (GPx), hydrogen peroxide (H2O2) and malonaldehyde (MDA) content as well as the accumulation of UV-absorbing compounds and endogenous ABA concentrations among different organs in both populations. In contrast, exogenous ABA showed significant decrease in A and significant increases in activities of SOD and GPx, H2O2, MDA content and the endogenous ABA concentrations. Compared with the low altitude population, the high altitude population was more tolerant to enhanced UV-B and exogenous ABA. Significant interactions between UV-B and ABA were observed in A, E, activities of SOD and GPx, as well as in endogenous ABA in leaves and roots of both populations. Across all treatments, C and N content in leaves was strongly correlated with those were in stems and roots, respectively. Additionally, leaf and stem N content were significant correlated with stem C content.

贡嘎山植物小枝功能性状在不同生活型和不同海拔间的比较研究

植物功能生态学研究不仅提供了植物生理生态学与生态系统生态学的连接，还为植物种群生活史对策研究提供了材料。Westoby 等 (2002) 提出了利用植物功能性状变量的主导维度来确定和量化植物生活史的生态适应策略。在他们所提出四个主导维度中，叶大小－小枝大小是研究相对较少的一维；其内部各组分的关系、对环境的响应，以及与其它重要维度的关系，目前的理解非常有限。 本研究以贡嘎山不同海拔不同功能群物种为研究对象，采用种间比较和系统发生独立性比较等研究方法，系统研究了植物的功能特征及其相关性在不同生境及不同功能群间的差异，旨在分析不同功能群物种的叶大小－小枝大小的成本和收益。其研究结果将有助于我们理解植物生活史对策的进化，进而理解物种共存和维持物种多样性的机制。主要研究结果如下： 1. 叶大小－小枝大小关系 小枝茎横截面积与单叶面积和总叶面积均呈异速生长关系，即总叶面积和单叶面积的增加比茎横截面积的增加速度快。但是，总叶面积和叶片干重的增加却基本上与小枝茎干重的增加等速。系统发生独立性比较研究的结果与此相一致。表明，在某一给定的茎投入时，至少大叶大枝物种不比小叶小枝物种在支撑叶面积和叶片干重方面具有优势。同时，在某一给定的小枝茎投入时，常绿阔叶物种比落叶阔叶物种支撑更少的叶面积。在茎干重与总叶面积的关系中，落叶复叶物种比落叶单叶物种具有更高的y轴截距，表明复叶物种比单叶物种在展叶面积方面更有效。复叶物种与单叶物种相比，通常具有较大的叶大小和小枝大小。 2. 叶大小－叶数量关系 叶大小与数量间在不同的叶片习性、不同的叶片形态以及不同的生境类型的物种间均存在稳定的负的等速生长关系，且这种关系在系统发生独立性比较时依然成立。然而，在某一给定的出叶强度 (单位小枝的叶数量) 时，常绿阔叶物种比落叶物种具有更小的叶面积。而在给定体积基础上的出叶强度时，落叶复叶物种的叶面积显著大于落叶单叶物种，且复叶物种比单叶物种具有更大的叶大小和更小的出叶强度。但是，叶大小与数量间的关系在不同的海拔间并没有显著的差异。 3. 小枝大小－总叶面积关系 在不同的生活型或不同的生境下，小枝上总叶面积与茎干重和小枝干重均呈正的异速生长关系，且斜率显著小于1.0，表明小枝上总叶面积的增加都不能赶上小枝及茎大小的增加。这种“收益递减”表明随着小枝干重的增加，光截取的收益递减。此外，叶面积比 (总叶面积与小枝干重的比值) 与单叶干重呈显著负相关关系，系统发生独立性比较的结果与此相一致。根据以上结果，可以推测，大叶的物种在质量较好的生境中出现，而群落内部小枝茎的寿命较长的物种可以拥有较大的叶片。 4. 叶片色素浓度－LMA关系 随着海拔的升高，阔叶木本植物和草本植物的叶片色素浓度减少，叶绿素a/b和类胡萝卜素/叶绿素比值以及比叶重 (LMA) 增加。然而，在草本植物中的色素浓度、色素比值和LMA的变化比阔叶木本植物的更明显。同时，LMA与叶片色素浓度呈负相关关系，但是在落叶物种中的LMA对色素浓度的影响比常绿阔叶物种更强烈。总之，草本植物的叶片特征对海拔梯度的变化似乎比木本植物更敏感，LMA对叶片色素的保护作用在落叶物种中比在常绿阔叶物种显得更重要。这些结果表明不同生活型物种可能采取不同的保护机制来降低叶绿体器官的损伤和增加他们的碳获取能力。 Studies on plant functional ecology not only bridge plant eco-physiology and ecosystem functioning, but also enrich plant population biology. As pointed out by Westoby et al (2002), plant life history strategies can be identified and quantified by four leading dimensions of variations in plant functional traits, i.e., seed size/output, leaf mass per area and leaf life span, plant height, and leaf size-twig size. Compared to the other dimensions, the cost/benefit of the leaf size-twig size spectrum has scarcely been analyzed in relation to environmental gradients and life form types, and the adaptive significance of this spectrum is not fully understood. In the present study, the relationships between functional traits of plant twigs are determined for the species with different life forms along an altitudinal gradient of Gongga Mountain with both cross-species analysis and evolutionary divergence analysis. The primary objective of this study is to examine the cost/benefit of leaf size-twig size in plants. The study results are supposed to provide insights into the understanding of the mechanism of species coexistences. The results are shown in the following. 1. The relationship between leaf size and twig size Twig cross-sectional area allometrically scaled with both individual leaf area and total leaf area supported by the twigs. However, the increase in total lamina mass/area was generally proportional to the increase in stem mass. These correlations between trait variations were significant in both interspecies analysis and phylogenetically independent comparison (PIC) analysis, which indicated that thick-twigged/large-leaved species, at least, do not have an advantage in supporting leaf/lamina area and lamina mass for the same twig stem investment than thin-twigged/ small-leaved species. Meanwhile, the evergreen broad-leaved species supported a smaller leaf area for the same twig stem investment in terms of both cross-sectional area and stem mass than the deciduous species. The deciduous compound-leaved species have a higher y-intercept in the scaling relationship of twig stem mass versus total leaf area than the deciduous simple-leaved species, indicating that compound-leaved species were more efficient in displaying leaf area. The compound-leaved species were larger in both leaf size and twig size than their counterpart in the present study. 2. The relationship between leaf size and leaf number Significantly negative and isometric scaling relationships between leaf size and leafing intensity (leaf number per twig mass or volume) were found to be consistently conserved across species independent of leaf habit, leaf form and habitat type. The negative correlations between leaf size and leafing intensity were also observed across correlated evolutionary divergences. However, leaf area was smaller in the evergreen broad-leaved species at a given leafing intensity than in the deciduous species. The deciduous compound-leaved deciduous species were higher in leaf area than deciduous simple-laved species at a given volume-based leafing intensity. Moreover, the compound-leaved deciduous species were larger in leaf size but smaller in leafing intensity than their simple counterparts. No significant difference was found in the scaling relationships between altitudes. 3. The relationship between twig size and total leaf area Leaf area was found to scale positively and allometrically with both stem and twig mass (stem mass plus leaf mass) with slopes significantly smaller than 1.0, independent of life form and habitat type, indicating that the increase in total leaf area fails to keep pace with increasing twig size and stem size. This ‘diminishing returns’ suggests that the benefit of light intercept decreased with increasing twig mass. Moreover, the leaf area ratio (the ratio of total leaf area to stem or twig mass) correlated negatively with individual leaf mass. The results of PIC were consistent with the correlations. According to the results, it is speculated that large-leaved species may be favored when habitat is good and when stem longevity are long within community. 4. The relationship between leaf pigment concentrations and leaf mass per area With increasing altitude, the concentrations of pigments decreased, but the ratios of chlorophyll a/b and carotenoid/chlorophyll, and LMA increased, in both the broad-leaved woody species and herbaceous species groups. However, the changes in the pigment concentrations, ratios and LMA were more profound in the herbaceous species than in the woody species. In addition, pigment concentrations were negatively correlated with LMA in each life form type and in the pooled dataset. However, the LMA effect on leaf pigment concentrations was more profound in the deciduous species than in the evergreen braode-leaved species. In general, herbaceous species seemed more sensitive to the increasing altitude compared to woody species, and LMA seemed to be a more important mechanism for protecting leaf pigments in deciduous species than in evergreen broad-leaved species. These results suggested that the species with different life forms may employ different protective mechanisms to decrease the chloroplast apparatus damage and increase their carbon gain.

黄土塬区氮磷配施对冬小麦光合作用、产量形成及水分利用的影响

在黄土高塬沟壑区,研究了不同施肥条件对冬小麦各个生育期的叶面积指数、光合作用、干物质积累、产量形成以及水分利用的影响,结果表明:与对照相比,施肥后小麦叶面积指数和光合速率都显著提高,同化作用增强,平均产量提高了47.6%,水分利用效率提高了24.6%。不同的肥料配施对冬小麦的干物质积累、产量以及水分利用效率的影响顺序基本一致,即高氮高磷>高氮低磷>低氮低磷>低氮高磷,但方差分析表明,在这种氮磷配施方案中起作用的主要是氮肥,磷肥的贡献不大,且二者并没有产生明显的交互作用。

土壤改良剂与氮肥配施对玉米生长及其养分含量的影响

采用盆栽试验研究了秸秆配方、废料配方和胶土配方3种改良剂与氮肥配施对玉米植株生长状况、生物量、叶绿素含量、全N及全P含量的影响。结果表明:3种改良剂与0.5 g/盆氮肥配施可以显著提高株高、茎粗、叶面积、地上地下生物量、叶绿素含量及植株全N含量,且以秸秆配方配施效果最佳,过量施用氮肥(1.0 g/盆)时,各指标与0.5 g氮肥水平下的值相比增加幅度甚小,茎粗和地下生物量甚至有下降的趋势。改良剂因素和氮肥因素对全P含量也有一定的影响,但二者交互作用对其并未产生显著性影响。因此,在施加改良剂的条件下可以适当地减少肥料的使用量,在满足植物体吸收利用前提下,既减少了养分投入和浪费,又减轻了对环境的污染。

水肥空间组合对冬小麦生物学性状及生物量的影响

目的】研究水肥空间组合对冬小麦形态指标及生物量的影响,对指导旱地施肥具有一定理论和实践意义。【方法】以肥熟土垫旱耕人为土为供试土壤,在全生育期遮雨和人工控制土壤水分条件下,采用分层隔水土柱试验法研究与田间土层分布相同土柱不同土层水分、氮、磷组合对冬小麦叶面积、株高、分蘖数、生物量、根冠比和收获指数等指标的影响。【结果】与整体湿润水分处理相比,上干下湿水分处理(0～30cm土层干旱胁迫,30～90cm土层湿润)下,抽穗期小麦旗叶面积、株高分别降低7.03%和3.77%;小麦地上部和根系生物量及收获指数也不同程度降低,但根冠比增加。从肥料处理看,单施磷和氮磷配施处理,小麦叶面积、株高、有效分蘖数和总生物量均极显著高于单施氮和CK,这与供试土壤各土层严重缺磷,而氮素供应相对丰富有关。从不同土层施肥看,在两种水分处理下,单施氮时,以均匀施入0～90cm土层小麦叶面积、株高、有效分蘖数、地上部生物量和根系生物量最高,施入0～30cm土层最低;单施磷和氮磷配施时,0～90cm与0～30cm土层施肥间总叶面积、旗叶面积、株高、有效分蘖数以及总生物量差异不显著,但均显著高于30～60cm和60～90cm土层相应施肥处理。【...

栽培模式、施氮和品种对冬小麦冠层结构和产量的影响

在黄土高原南部半湿润易旱区土垫旱耕人为土上进行大田试验,研究氮肥、品种和栽培模式对冬小麦叶面积指数(LAI)和透光率(DIFN)及产量的影响。结果表明,小麦生长过程中LAI先增大后减小,在开花期最大,成熟期最小,施氮能够显著增加LAI;DIFN的变化规律与LAI相反。不同品种间LAI和DIFN差异显著。全程覆膜和覆膜150 d的LAI极显著大于常规栽培、集雨面栽培和三密一稀栽培模式,DIFN与此相反;施氮后籽粒产量极显著增加。在不同栽培模式下,以全程覆膜、覆膜150 d和集雨面栽培模式的产量较高,但从维持土壤质量角度考虑,则覆膜150 d和集雨面2种栽培模式优于其它几种栽培模式;从冠层结构特征分析,这2种栽培模式更有利于增加群体光合能力。

有机钾肥在日光温室蔬菜上的应用效果研究

对陕北黄土高原日光温室大棚蔬菜黄瓜、大青菜、油麦菜和西芹进行了叶面喷施富万钾有机钾肥的田间试验研究。结果表明,在日光温室大棚蔬菜上施用有机钾肥,黄瓜植株高度、叶片数、茎粗、叶面积、瓜长均增加。大青菜的茎粗增长44%。油麦菜的株高、茎粗、地上植株、地下根重、总生物量均明显增加。西芹的株高、茎粗、地上植株、地下根重以及总生物量增加。富万钾有机钾肥能明显促进蔬菜生长,提高产量。

Changes in individual plant traits and biomass allocation in alpine meadow with elevation variation on the Qinghai-Tibetan Plateau

Plant traits and individual plant biomass allocation of 57 perennial herbaceous species, belonging to three common functional groups (forbs, grasses and sedges) at subalpine (3700 m ASL), alpine (4300 m ASL) and subnival (>= 5000 m ASL) sites were examined to test the hypothesis that at high altitudes, plants reduce the proportion of aboveground parts and allocate more biomass to belowground parts, especially storage organs, as altitude increases, so as to geminate and resist environmental stress. However, results indicate that some divergence in biomass allocation exists among organs. With increasing altitude, the mean fractions of total biomass allocated to aboveground parts decreased. The mean fractions of total biomass allocation to storage organs at the subalpine site (7%+/- 2% S.E.) were distinct from those at the alpine (23%+/- 6%) and subnival (21%+/- 6%) sites, while the proportions of green leaves at all altitudes remained almost constant. At 4300 m and 5000 m, the mean fractions of flower stems decreased by 45% and 41%, respectively, while fine roots increased by 86% and 102%, respectively. Specific leaf areas and leaf areas of forbs and grasses deceased with rising elevation, while sedges showed opposite trends. For all three functional groups, leaf area ratio and leaf area root mass ratio decreased, while fine root biomass increased at higher altitudes. Biomass allocation patterns of alpine plants were characterized by a reduction in aboveground reproductive organs and enlargement of fine roots, while the proportion of leaves remained stable. It was beneficial for high altitude plants to compensate carbon gain and nutrient uptake under low temperature and limited nutrients by stabilizing biomass investment to photosynthetic structures and increasing the absorption surface area of fine roots. In contrast to forbs and grasses that had high mycorrhizal infection, sedges had higher single leaf area and more root fraction, especially fine roots.

Relationships between precipitation, soil water and groundwater at Chongling catchment with the typical vegetation cover in the Taihang mountainous region, China

Vegetation cover plays an important role in the process of evaporation and infiltration. To explore the relationships between precipitation, soil water and groundwater in Taihang mountainous region, China, precipitation, soil water and water table were observed from 2004 to 2006, and precipitation, soil water and groundwater were sampled in 2004 and 2005 for oxygen-18 and deuterium analysis at Chongling catchment. The soil water was sampled at three sites covered by grass (Carex humilis and Carex lanceolata), acacia and arborvitae respectively. Precipitation is mainly concentrated in rainy seasons and has no significant spatial variance in study area. The stable isotopic compositions are enriched in precipitation and soil water due to the evaporation. The analysis of soil water potential and isotopic profiles shows that evaporation of soil water under arborvitae cover is weaker than under grass and acacia, while soil water evaporation under grass and acacia showed no significant difference. Both delta O-18 profiles and soil water potential dynamics reveal that the soil under acacia allows the most rapid infiltration rate, which may be related to preferential flow. In the process of infiltration after a rainstorm, antecedent water still takes up over 30% of water in the topsoil. The soil water between depths of 0-115 cm under grass has a residence time of about 20 days in the rainy season. Groundwater recharge from precipitation mainly occurs in the rainy season, especially when rainstorms or successive heavy rain events happen.