Growth and yield analysis in different methods of beet (Cv. 'tall top early wonder') plantation

This objective of this study was to evaluate the effects of different methods of red beet seedling production and direct sowing on the development of the plant in field conditions. 'Tall Top Early Wonder' was used as the cultivar. The experimental design was a randomized blocks with 4 replications of each treatment: T1 - seedling produced in trays of 288 cells; T2 - 200 cells; T3 - 128 cells; T4 - 128 cells; T5 - direct sowing and T6 - bare-root seedling. The seedlings produced in trays and bare root seedlings were transplanted in the field 28 DAS with spacing of 0.20 x 0.10m. The mean height of plants, leaf area, leaf dry matter, petiole dry matter, shoot dry matter, root dry matter, relationship between shoot dry matter and root dry matter, absolute growth rate, relative growth rate, net assimilation rate, leaf area ratio and specific leaf area were determined. Storage root fresh matter and mean storage root diameter were determined starting from 77 DAS. Initial growth of the plants were superior for the direct sowing, resulting in smaller RGR and NAR than the other treatments. Independent of the production method, an increase of the cycle of the crop was verified. T6 had larger delay in the initial development. There was no difference for productivity. Method T1, had less expenses with respect to substrate and space in the vegetation home, without reduction in production.

薇甘菊对其入侵地植物种子萌发和幼苗生长的化感影响

薇甘菊主要入侵我国华南的广东、海南和云南三省，给当地造成了严重的危害，其强烈的化感作用被认为是其成功入侵的原因之一。而目前对薇甘菊化感作用的研究还较少，因而对薇甘菊化感作用的认识还有待深入的研究。另外，在对入侵植物入侵群落进行恢复时，由于入侵植物的凋落物以及生长过的土壤都还含有化感物质，常常导致恢复难以继续。因而选择抗化感能力强的物种来恢复薇甘菊的入侵地也成为该研究的一个主题。本文以薇甘菊为实验材料来研究薇甘菊化感作用对植物种子活力、种子萌发和幼苗生长的影响，同时筛选化感抗性强的物种以进行薇甘菊入侵地的恢复工作。其主要结论如下： 1、薇甘菊根和叶的提取液对植物种子活力、种子萌发和幼苗生长都有很大的抑制作用，并且这种抑制作用随着提取液浓度的升高以及处理时间的延长而加强，这证明了薇甘菊具有很强的化感作用。 2、一些植物种子萌发和幼苗生长在低、中浓度提取液以及高浓度提取液的短时间的处理下能被促进，不过在高浓度的提取液以及长时间的处理下都被抑制，这说明化感作用是抑制还是促进作用在很大程度上受到提取液浓度和处理时间的影响。 3、薇甘菊提取液（50 g L-1）对紫薇(Lagerstroemia indica)、刺槐(Robinia pseudoacacia)、黑麦草(Lolium perenne)和西葫芦（Cucurbita pepo）种子处理50-100 h就能极大的影响到其后的种子萌发和幼苗生长，这说明薇甘菊在短时间（50-100 h）就能给植物产生极强的化感作用，也进一步证实薇甘菊很强的化感作用。 4、由于各物种进化历史的不同，而且各物种在对薇甘菊的化感抗性上也存在着差异，所以各物种对薇甘菊提取液的化感反应也各不相同。 5、薇甘菊根提取液对刺槐和紫薇幼苗根的生长的影响要大于叶提取液对刺槐和紫薇幼苗根的生长的影响，而对刺槐和紫薇种子萌发率、初始萌发时间、萌发速率以及幼苗株高的影响却是叶提取液的化感作用强。这支持了一个新的假设：由于物种间代谢的多样性，至少在根和叶对受试植物根的化感影响方面，对于一些物种来说根的化感作用可能强于叶的化感作用，对于另一些物种来说叶的化感作用可能强于根的化感作用。 6、薇甘菊叶提取液对西葫芦种子活力、种子萌发和幼苗生长的化感影响大，而对其后开花时间以及开花的数目没有明显的影响，这说明薇甘菊对西葫芦生活史前期的化感影响要大于对西葫芦生活史后期的化感影响。 7、薇甘菊叶的水提取液对种子萌发的抑制作用要大于对幼苗生长的抑制作用;对非豆科植物种子萌发的影响要大于对豆科植物种子萌发的影响，而对非豆科植物幼苗生长的影响要小于对豆科植物幼苗生长的影响;对本地种的抑制作用要大于对外来归化种的抑制作用。 本研究证实了薇甘菊强烈的化感作用，根提取液对受体植物幼根生长的影响大于叶提取液对受体植物幼根生长的影响，这种化感作用可能极大的促进了薇甘菊的入侵。另外，在恢复薇甘菊入侵群落时，考虑到薇甘菊的化感作用，理应选择外来的已经归化了的非豆科植物的幼苗。

沙埋与供水对毛乌素沙地两种重要植物幼苗生长的影响

近年来，土地荒漠化（ Desertification）及其防治已成为世界各国政府及科学界广泛关注的社会与环境问题。毛乌素沙地是我国荒漠化发展的中心地区之一。荒漠化不仅长期制约着地方经济的发展，同时也不同程度地影响着黄河中下游等地区的生态环境。因此，毛乌素沙地退化生态系统的恢复重建势在必行。沙埋与水分是该地区重要的生态因子和限制因子。柠条（Caragana korshinskii ）和羊柴（Hedysarum laeve ）作为该地区广泛分布的物种，经常用于我国北方干旱、半干旱区的生态恢复。因此，本文以这两个物种为研究对象， 探讨不同的沙埋与供水对两种植物幼苗存活与生长的影响。该研究对深化与丰富植物对沙生环境适应的生态学机理认识， 进而对采用合理的方法进行荒漠化防治及当地生态系统恢复重建具有重要的理论与实际意义。 以柠条（Caragana korshinskii ）和羊柴（Hedysarum laeve ）这两种植物幼苗为研究对象，人工控制6 个沙埋深度、5 个沙埋时间和4 个水分梯度，研究它们对不同沙埋深度和供水量的响应。结果表明：适量的沙埋(0.25~0.50 H 沙埋)与供水(柠条50 mm/月，羊柴75 mm/月)可以促进幼苗生长，过量的沙埋与供水则会抑制生长甚至导致幼苗死亡。柠条幼苗在50 mm/月供水， 0.25、0.50 H 沙埋， 羊柴幼苗在75 mm/月供水，0.25、0.50 H 沙埋下具有较高的生物量、叶面积、相对生长速率和净同化速率；幼苗在1.0 H 和1.25 H 沙埋下全部死亡。供水量较小、沙埋较浅时，两种植物根冠比均较高；当供水量最大时，柠条幼苗根冠比在沙埋最深和没有沙埋时较大，而羊柴幼苗根冠比仍在没有沙埋时最高。

水分亏缺和凋落物水浸液对云杉幼苗生长和种子萌发的影响

在人类活动导致全球变暖的前提下，由于全球气温的升高，地表水分加速向空中蒸发。从20世纪70年代至今，地球上严重干旱地区的面积几乎扩大了一倍。这一增长的一半可归因于气温升高而不是降雨量下降，因为实际上同期全球平均降水量还略有增长。干旱对陆地植物和农林生态系统产生深远影响，并已成为全球变化研究的一个重要方面。位于青藏高原东部的川西亚高山针叶林是研究气候变暖对陆地生态系统影响的重要森林类型。森林采伐迹地、人工林下和林窗环境作为目前该区人工造林和森林更新的重要生境，其截然不同的光环境对亚高山针叶林更新和森林动态有非常重要的影响。凋落物产生的化感物质可通过影响种子萌发和早期幼苗的定居而影响种群的建立和更新，而人工林和自然林物种以及更新速度的差异性也都受凋落物的影响。 云杉是川西亚高山针叶林群落的重要树种之一,在维持亚高山森林的景观格局和区域生态安全方面具有十分重要的作用，其自然更新能力及其影响机制一直是研究的热点问题。本试验以云杉种子和2年生幼苗为研究对象，从萌发、根尖形态、幼苗生长、光合作用、渗透调节和抗氧化能力等方面研究了不同光环境下水分亏缺和凋落物水浸液对云杉种子和幼苗生长的影响。旨在从更新的角度探讨亚高山针叶林自然更新的过程，其研究成果可在一定程度上为川西亚高山针叶林更新提供科学依据，同时也可为林业生产管理提供科学指导。主要研究结论如下： 水分亏缺在生长形态、光合作用、抗氧化能力、活性氧化对云杉幼苗都有显著影响。总体表现为，水分亏缺导致了云杉幼苗的高度、地径、单株总生物量降低，增加了地下部分的生长；水分亏缺显著降低了云杉叶片中相对含水量、光合色素、叶氮含量，净光合速率和最大量子产量(Fv/Fm)，提高了幼苗叶片中膜脂过氧化产物（MDA）的含量；水分亏缺提高了幼苗叶片中过氧化氢(H2O2)含量，超氧荫离子（O2-）生成速率以及脯氨酸和抗氧化系统的活性（ASA, SOD, CAT, POD, APX和GR）。从这些结果可知，植物在遭受水分亏缺导致的伤害时，其自身会形成防御策略，并通过改变形态和生理方面的特性以减轻害。但是，这种自我保护机制依然不能抵抗严重水分亏缺对植物的伤害。 模拟林下低光照条件显著增加单株植物的地上部分生长，尤其是其叶片的比叶面积（叶面积/叶干重），同时其光合色素含量和叶片相对含水量也显著增加，这些改变直接导致植株光合速率和生物量的增加。同时，与高光照水平相比，低光照幼苗的膜脂过氧化产物（MDA）和活性氧物质均较低，显示出低光照比高光照水平对植物的更低的氧化伤害。尽管低光照也导致大部分抗氧化酶活性降低，但这正显示出植物遭受低的氧化伤害，更印证了前面的结论。 凋落物水浸液影响了云杉种子的萌发和根系的生长，更在形态、光合作用、抗氧化能力、活性氧物质以及叶氮水平上显著影响了云杉幼苗，其中，以人工纯林凋落物的影响更有强烈。具体表现在，种子萌发速率和萌发种子幼根的长度表现为对照>自然林处理>人工纯林；凋落物水浸液抑制种子分生区和伸长区的生长，人工林处理更降低了根毛区的生长，使根吸水分和养分困难。对2年生幼苗的影响主要表现在叶绿素含量、光合速率以及叶氮含量的降低；膜脂过氧化产物、活性氧物质和抗氧化酶系统的显著增加。同样的，人工纯林处理对云杉幼苗的影响显著于自然林处理。 在自然生态系统中，由于全球变暖气温升高导致的水分亏缺和森林凋落物都存在森林的砍伐迹地，林窗和林下环境中。我们的研究表明，与迹地或林窗强光照比较，林下的低光照环境由于为植物的生长营造了较为湿润的微环境，因此水分亏缺在林下对云杉幼苗造成的影响微弱。这可以从植物的形态、光合速率以及生物量积累，过氧化伤害和抗氧化酶系统表现出来。另一方面，凋落物水浸液在模拟林下低光照环境对植物的伤害也微弱于强光照环境，这与强光照环境高的水分散失导致环境水分亏缺有关；而人工纯林处理对云杉幼苗的伤害比对照和自然林处理显示出强烈的抑制作用。 Under the pre-condition of global warming resulted from intensive human activities, water in the earth’s surface rapidly evaporates due to the increase of global air temperature. From 1970s up to now, the area of serious drought in the world is almost twice as ever. This increase might be due to the increasing air temperature and not decreasing rainfall because global average rainfall in the corresponding period slightly is incremental. Drought will have profound impacts on terrestrial and agriculture-forest system and has also become the important issue of global change research. The subalpine coniferous forests in the eastern Qinghai-Tibet Plateau provide a natural laboratory for the studying the effects of global warming on terrestrial ecosystems. The light environment significantly differs among cutting blanks, forest gap and understory, which is particularly important for plant regeneration and forest dynamics in the subalpine coniferous forests. Picea asperata is one of the keystone species of subalpine coniferouis forests in western China, and it is very important in preserving landscape structure and regional ecological security of subalpine forests. The natural regeneration capacities and influence mechanism of Picea asperata are always the hot topics. In the present study, the short-term effects of two light levels (100% of full sunlight and 15% of full sunlight), two watering regimes (100% of field capacity and 30% of field capacity), two litter aqueous extracts (primitive forest and plantation aqueous extracts) on the seed germination, early growth and physiological traits of Picea asperata were determined in the laboratory and natural greenhouse. The present study was undertaken so as to give a better understanding of the regeneration progress affected by water deficit, low light and litter aqueous extracts. Our results could provide insights into the effects of climate warming on community composition and regeneration behavior for the subalpine coniferous forest ecosystem processes, and provide scientific direction for the forest production and management. Water deficit had significant effects on growth, morphological, physiological and biochemical traits of Picea asperata seedlings. Water deficit resulted in the decrease in height, basal diameter, total biomass and increase in under-ground development; water deficit significantly reduced the needle relative water content, photosynthetic pigments, needle nitrogen concentration, net photosynthetic rate and the maximum potential quantum yield of photosynthesis (Fv/Fm), and increased the degree of lipid peroxidation (MDA) in Picea asperata seedlings; water deficit also increased the rate of superoxide radical (O2-) production, hydrogen peroxide (H2O2) content, free proline content and the activities of antioxidant systems (ASA, SOD, POD, CAT, APX and GR) in Picea asperata seedlings. These results indicated that some protective mechanism was formed when plants suffered from drought stress, but the protection could not counteract the harm resulting from the serious drought stress on them. Low light in the understory significantly increased seedling above-ground development, especially the species leaf area (SLA), and photosynthetic pigments and relative needle content. These changes resulted in the increase in net photosynthetic rate and total biomass. Moreover, the lower MDA content and active oxygen species (AOS) (H2O2 and O2-) in low light seedlings suggested that low light had weaker oxidative damage as compared to high light. Lower antioxidant enzymes activities in low light seedlings indicated the weaker oxidative damage on Picea asperata seedlings than high light seedlings, which was correlative with the changes in MDA and AOS. Litter aqueous extracts affected seed germination and root system of Picea asperata seedlings. Significant changes in growth, photosynthesis, antioxidant activities, active oxygen species and leaf nitrogen concentration were also found in Picea asperata seedlings, and plantation treatment showed the stronger effects on these traits than those in control and primitive forest treatment. The present results indicated that seed germination and radicle length parameters in control were superior to those in primitive forest treatment, and those of primitive forest treatment were superior to plantation treatment; litter aqueous extracts inhibited the meristematic and elongation zone, and plantation treatment caused a decrease in root hairs so as to be difficult in absorbing water and nutrient in root system. On the other hand, litter aqueous extracts significantly decreased chlorophyll content, net photosynthetic rate and leaf nitrogen concentration of Picea asperata seedlings; MDA, AOS and antioxidant system activities were significantly increased in Picea asperata seedlings. Similarly, plantation treatment had more significant effect on Picea asperata seedlings as compared to primitive forest treatment. In the nature ecosystem, water deficit resulted from elevating air temperature and litter aqueous extract may probably coexist in the cutting blank, forest gap and understory. Our present study showed that water deficit had weaker effects on low light seedlings in the understory as compared to high light seedlings in the cutting blank and forest gap. The fact was confirmed from seedlings growth, gas exchange and biomass accumulation, peroxidation and antioxidant systems. This might be due to that low light-reduced leaf and air temperatures, vapour-pressure deficit, and the oxidative stresses can aggravate the impact of drought under higher light. On the other hand, litter aqueous extracts in the low light had weaker effects on the Picea asperata seedlings than those at high light level, which might be correlative to the water evapotranspiration under high light. Moreover, plantation litter aqueous extracts showed stronger inhibition for seed germination and seedling growth than control and primitive forest treatments.

花椒水浸液及酚酸类化感物质对作物种子萌发和幼苗生长的影响效应

花椒（Zanthoxylum piperitum）是川西干旱河谷地区的重要经济作物，化感作用是花椒连作障碍的原因之一。系统研究花椒化感作用有助于深入理解并最终解决花椒连作障碍。本文通过研究花椒叶、林下土壤浸提液及单一纯化感物质对花椒幼苗生长、苜蓿种子萌发及幼苗生长的影响作用，从生理生化角度揭示浸提液及纯化感物质的作用方式。通过室外和室内模拟实验，对浸提液及纯化感物质的化感效应进行比较，为花椒连作障碍的解决和化感作用机制的深入理解提供依据。主要结果如下： 1.花椒叶及林下土壤浸提液对地下生物量影响作用强与对地上生物量的化感效应，两种浸提液的化感效应强度不同，叶浸提液作用表现更显著。其中在Y6、Y8 、T6和T8处理时，花椒幼苗地下生物量分别降低了31.2%、32.1%、31.6%和31.7%。 2.两种浸提液均能显著影响花椒幼苗体内的保护性酶活性，总体说来，在高浓度下抑制各种抗氧化物酶活性，幼苗体内丙二醛含量增加，幼苗受害严重；在较低浓度下，各种保护性酶活性有所增加，丙二醛含量减少，幼苗伤害减轻。同时，不同月份里，各种酶的活性高低显著不同，9月份的活性显著低于7月份的酶活性。对于养分含量的影响，Y8、T8的影响强度最大，分别使碳元素含量降低了27.8%和30.8%，使钾元素含量降低了34.7%和25.6%。 3.花椒叶及林下土壤浸提液对苜蓿种子萌发及幼苗生长有化感作用，表现在最终萌发率、不同物质代谢及保护性酶活性的差异上。两种浸提液对苜蓿种子萌发过程中蛋白质的含量均无显著性影响，对淀粉和可溶性糖的影响作用类似，高浓度处理无明显化感效应，较低浓度处理显著降低二者在萌发苜蓿种子中的含量。Y2、Y4与T4处理分别使可溶性糖含量减少了32.3%、29.1%和18.8%，Y2与T2处理分别使淀粉含量降低了29.3%和26.8%。 4.苜蓿种子在4种单一化感物质最高浓度即10-3 mol•L-1处理下，萌发率显著降低，半数萌发时间推迟，随着处理浓度降低，抑制作用逐渐减弱，当降低到10-6 mol•L-1时，又能够表现出对苜蓿种子萌发的促进作用。 5.纯化感物质在10-6 mol•L-1时使苜蓿幼苗叶片的保护性酶活性显著升高，丙二醛含量显著降低；在10-3 mol•L-1时使苜蓿叶片中保护性酶活性显著降低，丙二醛含量增加，膜脂过氧化程度加重。 Zanthoxylum piperitum is one of the most important cash crops and has been extensively cultivated in Eastern Tibetan Plateau, especially in the fragile dry valley areas. Allelopathic effects could be a reason for Z. piperitum’s continuous cropping impediment. Systemmatically research of the effect of Z. piperitum allelopathy could help to comprehend the continuous cropping impediment. The allelopathic effects on seedlings growth and seed germination of aqueous extracts of Zanthoxylum piperitum and phenolic allelochemicals were studied, and the action mechanism of the two substances was also discussed from physiology. Indoor and outdoor experiments were set to compare the difference between aqueous extracts and pure allelochemicals. The main results showed that: 1. The aqueous extracts of leaf and soil had significant allelopathic effects on aboveground and underground biomass, but the effect on underground biomass was stronger than the effect on underground evidently. Treated with Y6、Y8 、T6 and T8, the underground biomass was reduced 31.2%、32.1%、31.6% and 31.7% respectively. 2. The activity of activities of superoxide dismutase, catalase, peroxidase and ascorbate peroxidase were significantly reduced, while the content of MDA was increased and the seedlings were suffered stronger, when treated by the high concentration; but at the low concentration, these were reversed. And then, at the different month, the activities of antioxidant enzyme were significantly distinct. As for the contents of nutrient element, Y8、T8 had the more intensive effects than other treatments. 3. The results showed that the two types of aqueous extracts had significant allelopathic effects on seed germination, substances metabolize and the activity of antioxidant enzyme. But the aqueous extracts had no effects on the content of protein, while had the similar effects on the content of starch and soluble sugar. At Y2、Y4 and T4, the content of soluble sugar decreased 32.3%、29.1% and 18.8% respectively. 4. Treated with 10-3 mol•L-1 of the four allelochemicals, the seed germination of alfalfa was significantly inhibited. Ferulic acid, coumarin and vanillic acid at 10-3 mol•L-1 significantly reduced the activities of antioxidant enzyme, while the content of MDA in alfalfa seedling was significantly increased. The restrain effects became weakened with the treat concentration falled. However, ferulic acid, coumarin and vanillic acid could increase the activities of antioxidant enzyme at 10-6mol•L-1.

模拟增温与UV-B 辐射增强对云杉种子萌发和幼苗生长的影响

臭氧层损耗导致的地球表面UV-B辐射增强以及温室气体增多引起的气候变暖是当今两大全球环境问题。UV-B辐射增强和气候变暖对陆地植物和生态系统产生深远影响，并已成为全球变化研究的重要议题。作为世界第三极的青藏高原，UV-B 辐射增强以及气候变暖现象尤为突出。本试验所在林区是青藏高原东缘的主要林区，具有大面积的亚高山人工针叶成熟林，在全球变化背景下该森林的天然更新潜力如何是急待回答的重要问题。基于此，本研究围绕森林树种的种子和幼苗这一更新的重要阶段，开展了气候变暖、UV-B辐射增强和联合胁迫对云杉种子萌发及幼苗定居影响的研究，旨在全球变化背景下，探讨全球变暖、UV-B 辐射增强和联合胁迫是否对西南地区大面积人工亚高山针叶林更新的种子萌发和幼苗定居阶段产生影响。 本文以青藏高原东缘亚高山针叶林主要树种云杉为研究对象，研究云杉种子萌发及幼苗的生长和生理对UV-B辐射增强与气候变暖的响应。采用UV-B荧光灯（UV-lamp）来模拟增强的UV-B 辐射，此外，采用开顶式有机玻璃罩（OTCs）来模拟气候变暖。本试验包括四个处理：（1）大气UV-B 辐射+大气温度（C）；（2）大气UV-B 辐射+模拟气候变暖（W）；（3）增强的UV-B辐射+大气温度（U）；（4）增强的UV-B辐射+模拟气候变暖（U+W）。 根据本试验结果，UV-B辐射增强对云杉种子萌发没有显著影响，它对萌发云杉幼苗的影响主要体现在幼叶展开以后。根据两年的试验结果，增强的UV-B辐射降低了云杉幼苗抗氧化酶活性，降低了抗氧化物质的含量，此外，造成了膜质的过氧化，表现为MDA在针叶中的积累。增强的UV-B照射处理萌发云杉幼苗两年后，幼苗的生长受到显著抑制。我们的结果显示，OTCs分别提高了空气（10 cm）和土壤（5 cm）温度1.74℃和0.94 ℃。增温显著地促进了云杉种子提前萌发，提高了萌发速率和萌发比率，而且，明显地促进了幼苗的生长，表现为株高和生物量累积的显著增长。此外增温还有利于云杉幼苗根的伸长生长以及生物量的累积，这可以使云杉幼苗更好地利用土壤中的水分和营养元素。 根据本试验结果，温度升高显著地促进了增强UV-B辐射下云杉萌发幼苗的生长，这说明，温度升高缓解了UV-B辐射增强对云杉萌发幼苗的负面影响。这种缓解作用可能是温度升高对UV-B辐射增强处理下幼苗的抗氧化系统活性改善的结果。温度升高还缓解了高UV-B辐射对云杉幼苗根生长的抑制作用，这也可能是增温缓解伤害的原因之一。此外，根据我们的试验结果，增温与UV-B辐射增强联合作用（U+W）下云杉萌发幼苗的生长状况好于大气温度与大气UV-B辐射联合（C）处理，表现为株高、地径、根长和生物量积累均高于C处理，因此可以推断，UV-B辐射增强与气候变暖同时存在对萌发幼苗在两年之内的生长没有产生抑制作用，也就是说，气候变暖的缓解作用完全弥补了UV-B辐射增强的有害作用。 同样，增强的UV-B辐射显著影响了云杉幼苗的光合作用，表现为净光合速率（Pn）和表观量子效率（Φ）的提高，此外，根据我们的试验结果，它还造成了PSII的光抑制。增强的UV-B辐射显著抑制了云杉幼苗对营养元素的吸收，表现为大量营养元素、碳、钙、镁和锌含量的降低，但是，它却显著促进了铁在植株体内的积累。增温显著地提高了净光合速率，但是，它对光系统II（PSII）的光化学效率影响不大。温度升高缓解了UV-B增强对云杉幼苗光合作用的伤害，表现为净光合速率、表观量子效率以及PSII光化学效率的提高。此外，温度升高还缓解了UV-B辐射增强对离子吸收的抑制作用。 Enhanced UV-B radiation due to the reduction of O3 layer and global warming induced by increased greenhouse gases in the air have become the two pressing aspects of global climate changes. Moreover, enhanced UV-B radiation and warming have profound and long-term impacts on terrestrial plants and ecosystems, and the studies focusing on the two factors have attracted many attentions. Qinghai-Tibetan Plateau is the third in elevation in the world, and enhanced UV-B radiation and climate warming are especially prominent in this region. Our research located in the main forest belt in the eastern Qinghai-Tibetan Plateau where large areas of subalpine coniferous forests distributed. Based on that, we carried out a research to study the effects of enhanced UV-B radiation and climate warming on seed germination and seedlings growth of seedlings which are the important basic stage in forest regeneration. This research was arranged by a complete factorial design and included two factors (UV-B radiation and temperature) with two levels. The UV-lamps were used to manipulate the supplemental UV-B radiation and open-top chambers (OTCs) were adopted to increase temperature. The four treatments were: (1) C, ambient UV-B without warming; (2) U, enhanced UV-B without warming; (3) W, ambient UV-B with OTCs warming; (4) U+W, enhanced UV-B with OTCs warming. The main results were exhibited as follows: 1. Based on our results in this research, OTCs increased temperature on average 1.74℃ in air (10 cm above ground) and 0.92 ℃ in soil (5 cm beneath ground). Furthermore, OTCs also slightly reduced soil moisture and relative air humidity, however, the differences was not statistically significant. 2. Our results showed that enhanced UV-B had no significant effects on the seeds germination of P. asperata. Enhanced UV-B affected sprouts of P. asperata until the needles unfolded. During two years, enhanced UV-B inhibited the efficiency of the antioxidant defense systems, and as a result, it induced oxidant stress and the accumulation of MDA in needles. After two years of exposure to enhanced UV-B, the growth of P. asperata sprouts was markedly restrained compared with those under ambient UV-B radiation and temperature (C). Warming significantly stimulated the germination speed and increased the germination rate of P. asperata seeds. In the next place, it prominently facilitated the growth of P. asperata sprouts, represented as improvements in stem elongation and biomass accumulation. Furthermore, warming also increased root growth of P. asperata sprouts, which could made sprouts more efficient to use water and nutrient elements in soil. In this research, warming alleviated the deleterious effects of enhanced UV-B on P. asperata sprouts. It markedly stimulated the growth of P. asperata sprouts exposed to enhanced UV-B. The ease effects of warming on the abilities of the antioxidant defense systems might account for its amending effects on growth. After two years of exposure to enhanced UV-B radiation and warming, the growth of P. asperata sprouts was better than those under ambient UV-B radiation without warming (C), which could be seen from the higher plant height, basal diameter, root length and total biomass accumulation compared with C. 3. Enhanced UV-B radiation significantly influenced the photosynthesis processes of two-year old P. asperata seedlings. Our results showed that enhanced UV-B reduced the net photosynthetic rate (Pn) and the apparent quantum efficiency (Φ), and induced photoinhibition of photosynthetic system II (PSII). Enhanced UV-B significantly decreased the concentration of nitrogen (N), phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg) and zinc (Zn), however, it increased the accumulation of iron (Fe) in the whole plant of P. asperata seedlings. Warming significantly stimulated Pn of P. asperata seedlings but it had no prominent impacts on the photochemical efficiency of PSII. In our research, warming also alleviated the harmful effects of enhanced UV-B on photosynthesis and absorption of ions of P. asperata seedlings. It increased Pn, Φ and the photochemical efficiency of PSII in seedlings exposed to enhanced UV-B. Moreover, warming also increased the absorption of ions of the seedlings exposed to enhanced UV-B radiation.

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.

川西亚高山两种针叶树幼苗对增温和施氮的响应

人类活动引起全球大气中温室气体（CO2、CH4、NOx）浓度不断增加，致使地球表面温度在过去的100 年中已经增长了0.74 ± 0.18℃，预计到本世纪末将会增加1.1-6.4℃。此外，氮沉降也是当今社会的重要环境问题，随着经济发展的全球化, 高氮沉降也呈现出全球化趋势。全球气候变暖和氮沉降给陆地生态系统的地上、地下生物学和生物地球化学过程所带来巨大影响越来越引起人们的关注。 本文以川西亚高山针叶林的两个重要树种云杉和油松幼苗为研究对象，采用红外辐射增温（空气增温2.1℃，土壤增温2.6℃）和根部施氮（施氮量25 g N m-2yr-1）的方法，从生长形态、光合作用、抗氧化能力和矿质营养等方面研究这两种幼苗对气候变暖和氮沉降的响应。该实验为室外控制实验，包括四个处理：(1)不增温+不施氮（UU）；(2) 不增温+施氮（UF）；(3) 增温+不施氮（WU）；(4) 增温+施氮（WF）。本研究旨在从生理生化、物质代谢 、生长及形态等不同水平上研究模拟增温和施氮对两种树苗的联合效应，提高我们对全球变化下亚高山针叶林早期更新过程的理解，同时也为森林管理提供科学依据。具体研究结果如下： 单独增温处理显著提高了云杉和油松幼苗的地茎、叶重、茎重、根重以及总生物量；单独施氮处理也增加了两种幼苗的株高和总生物量。而增温和施氮联合作用对两种幼苗生长的影响并不相同，联合作用对云杉幼苗生长指标的正效应显著低于单独施氮处理，但是联合作用比单独增温或施氮更大程度的促进了油松幼苗生物量的积累。 单独增温和施氮都有利于提高云杉和油松叶片中叶绿素含量、净光合速率(A)、最大净光合速率(Amax)、表观量子效率（Φ）、最大光能转化效率（Fv/Fm）和量子产量（Y）。与对两种幼苗生长指标的影响相似，加氮和增温共同作用下油松幼苗的以上光合指标比在单独增温或施氮处理下有更大程度的提高；而联合作用下云杉幼苗叶绿素含量、净光合速率、最大净光合速率、表观量子效率、最大光能转化效率以及量子产量比单独施氮处理明显地降低。 增温和施氮都显著地降低了云杉和油松幼苗针叶组织中活性氧和丙二醛的积累。交互作用降低了云杉幼苗叶片的抗氧化酶活性、脯氨酸和ASA 的含量，却显著提高了油松幼苗SOD、POD、APX 等抗氧化酶的活性，并且对油松幼苗脯氨酸和ASA 积累的促进作用比单一因子更加明显。因此，增温和施氮共同作用下油松幼苗叶片中O2-产生速率、H2O2 及MDA 含量明显降低，而云杉叶片中只有O2-产生速率出现降低趋势。 增温和施氮都降低了云杉体内的P、Ca、Mg 元素的含量，增加了Cu、Zn、Mn 在各器官内的积累。对油松幼苗而言，增温和加氮单独作用也显著降低了Ca 含量增加了Cu、Zn、Mn 的积累，但是不同于云杉幼苗的是P、Mg 也显著增加。增温和施氮联合作用对云杉幼苗体内元素的影响与单一施氮处理或增温处理相似，不同的是比单一因子作用更为明显降低了P、Ca、Mg 含量，增加了植株中N、Cu、Zn、Mn 的含量，但是油松矿质元素含量在联合作用下并没有产生类似于云杉幼苗的双因子叠加效应。 总之，尽管单独增温或者施氮都有利于云杉和油松幼苗生长指标、光合能力以及抗氧化能力的提高。但是，增温和施氮对云杉幼苗生长生理的促进效应非但没有在交互作用下有更大的提高，反而低于单独氮处理。与此不同的是，增温和施氮联合作用比单因子作用更有利于油松幼苗生长及生理指标的提高。 With the continued increase in atmospheric concentrations of greenhouse gases (CO2、CH4、NOx), the mean global surface temperature has increased by about 0.74 ± 0.18℃ over the past century and is predicted to rise by as much as 6.4℃ during this century. Besides global warming, nitrogen deposition is another serious environmental problem caused by human activities, and high nitrogen load has become globalization as a result of global economy development. Global climate warming and nitrogen deposition have induced dramatic alternations in above - and below- ground biology and biogeochemistry process in terrestrial ecosystems, and more and more attention has been invited to those problems. This experiment mainly studies two important species Picea asperata and Pinus tabulaeformis in subalpine coniferous forest of western Sichuan, China. Infared heaters are induced to increase both air and soil temperature by 2.1℃ and 2.6 ℃, respectively. Ammonium nitrate solution (for a total equivalent to 25 g N m-2 year-1) is added to soil surface. There are four treatments in this study: (1) unwarmed unfertilized (UU); (2) unwarmed fertilized (UF); (3) warmed unfertilized (WU); (4) warmed fertilized (WF). This study is conducted to determine the influences of experimental warming and nitrogen fertilization on physiolchemistry, nutrition metabolism, growth and morphology in the two coniferous species seedlings. The current study is favorable for increasing our understanding on the early phase of regeneration behavior in subalpine coniferous forest, and it also provide scientific direction for forest management under future global changes. The results are as follows: Artificial warming alone significantly increased basal diameter, leaf mass, stem mass, root mass and total biomass for Picea asperata and Pinus tabulaeformis seedlings, and single nitrogen fertilization are also favorable for growth of the two species and stimulate plant hight and total biomass. The two species seedlings respond differently to the combination of elevated temperature and nitrogen addition. Warming combined with nitrogen fertilization weakens the positive effects of nitrogen addition for growth of Picea asperata seedlings. However, the combination of elevated temperature and nitrogen fertilization further increase biomass accumulation of Pinus tabulaeformis seedlings. Both elevated temperature alone and nitrogen fertilization alone can increase photosynthetic pigments contents, net photosynthetic rate (A), maximum net photosynthetic rate (Amax), apparent quantity yield (Φ), maximum photochemical efficiency of photosystem II (Fv/Fm) and effective quantum yield (Y). Similarly with growth parameters, the combination of warming and nitrogen addition induced more increment of these above photosynthetic parameters for Pinus tabulaeformis seedlings. However, these photosynthetic parameters of Picea asperata seedlings under the combination of warming and nitrogen addition are lower than those under nitrogen fertilization alone. The levels of active oxygen species (AOS) and malodiadehyde (MDA) in needles of the two coniferous species seedling are obviously decreased by experimental warming or additional nitrogen. Warming combined with nitrogen fertilizer reduces the activities of SOD, CAT and APX, and the contents of proline and ASA of Picea asperata seedlings, but the combination significantly increases activities of these antioxidant enzymes in needlels of Pinus tabulaeformis seedlings and further improves the accumulation of proline and ASA compared to either artificial warming or nitrogen addition. Therefore, the rate of O2 - production, the contents of H2O2 and MDA in needles of Pinus tabulaeformis seedlings are remarkably reduced by the combination of warming and nitrogen addition, but the combination only significantly decreased the rate of O2 - production of Picea asperata seedlings. Elevated temperature or nitrogen fertilization decrease the contents of P, Ca, Mg but increase Cu, Zn, Mn contents for Picea asperata seedlings. For Pinus tabulaeformis seedlings, elevated temperature alone and nitrogen fertilization alone decreased Ca, but increased P, Mg, Cu, Zn, Mn contents. The effects of the combination of warming and nitrogen addition on these element contents in needles of Picea asperata seedlings are added or multiplied the effects of warming and nitrogen addition alone, resulting in less contens of P, Ca, Mg and more contents of Cu, Zn, Mn than either elevated temperature or nitrogen fertilization. Howere, these adding or multipluing single-factor effects on contents of these elements are not observed in the case of Pinus tabulaeformis seedlings. In conclusion, growth parameters, photosynthetic capacities and antioxidant abilities of Picea tasperata and Pinus abulaeformis seedlings are improved by experimental warming or nitrogen fertilization. Interestingly, the positive effects of warming and nitrogen addition on growth and physiological performances are not multiplied by the combination of elevated temperature and nitrogen fertilization, even dempened for Picea asperata seedlings. However, for Pinus tabulaeformis seedlings, growth and physiological performances are further improved by the combination.

Physiological and Genetic Diversity Studies on Regeneration of Santalum Album L.

S. album L. is the source of highly priced and fragrant heartwood which on steam distillation yields on an average 57 per cent oil of high perfumery value. Global demand for sandalwood is about 5000-6000 tons/year and that of oil is 100 tons/year. Heartwood of sandal is estimated to fetch up to Rs. 3.7 million/ton and wood oil Rs.70,000-100,000/ kg in the international market. Sandal heartwood prices have increased from Rs. 365/ton in 1900 to Rs. 6.5 lakhs/ton in 1999-2000 and to Rs. 37 lakhs/ton in 2007. Substantial decline in sandalwood production has occurred from 3176 tons/year during 1960-‘ 65 to 1500 tons/year in 1997-98, and to 500 tons/year in 2007.Depletion of sandal resources is attributed to several factors, both natural and anthropogenic. Low seed setting, poor seed germination, seedling mortality, lack of haustorial connection with host plant roots, recurrent annual fires in natural sandal forests, lopping of trees for fodder, excessive grazing, hacking, encroachments, seedling diseases and spread of sandal spike disease are the major problems facing sandal. While these factors hinder sandal regeneration in forest areas, the situation is accelerated by human activities of chronic overexploitation and illicit felling.Deterioration of natural sandal populations due to illicit felling, encroachments and diseases has an adverse effect on genetic diversity of the species. The loss of genetic diversity has aggravated during recent years due to extensive logging, changing landuse patterns and poor natural regeneration. The consequent genetic erosion is of serious concern affecting tree improvement programme in sandal. Conservation as well as mass propagation are the two strategies to be given due importance. To initiate any conservation programme, precise knowledge of the factors influencing regeneration and survival of the species is essential. Hence, the present study was undertaken with the objective of investigating the autotrophic and parasitic phase of sandal seedlings growth, the effects of shade on morphology, chlorophyll concentration and chlorophyll fluorescence of sandal seedlings, genetic diversity in sandal seed stands using ISSR markers, and the diversity of fungal isolates causing sandal seedling wilt using RAPD markers. All these factors directly influence regeneration and survival of sandal seedlings in natural forests and plantations.

Allelopathy and phytotoxicity of Zanthoxylum rhoifolium Lam.

In Cerrado, Zanthoxylum rhoifolium Lam. stands out because it interferes with the growth and development of other plants. The preliminary phytochemical analyses showed the presence of polyphenols and flavonoids. The Z. rhoifolium extract inhibited the germination index (5 mg mL(-1)=0.5%; 10mg mL(-1)=37.(5%) and 20mg mL(-1)=85.5%) decreased the germination and the lettuce seedlings growth (roots and the hypocotyls) and reduced the mitotic index than control. The extract of 1000 mu g mL(-1)conc contained (165.20 mg and 45.74 mg, phenols and total flavonoids, respectively) and had higher antioxidant activity (80.52%). We concluded that Z. rhofolium possesses allelopathic potential.

Crescimento de mudas de Gonçalo-Alves (Astronium fraxinifolium) sob diferentes fontes e doses de nitrogênio

A degradação do cerrado e a perda de sua biodiversidade demandam a revegetação de áreas desse bioma, onde existem espécies com potencial de uso econômico e ambiental pouco conhecidos. Este trabalho teve o objetivo de avaliar o efeito de diferentes fontes e doses de nitrogênio sobre o crescimento de mudas de Gonçalo-Alves (Astronium fraxinifolium), espécie arbórea nativa do cerrado ameaçada de extinção. O experimento foi realizado em estufa na UNESP/Campus de Ilha Solteira. O solo utilizado (Latossolo Vermelho) foi coletado na profundidade de 0,0 a 0,20 m, em Selvíria (MS). As fontes de nitrogênio utilizadas ((NH4)2SO4, NH4NO3 e Ca(NO3)2) foram aplicadas nas doses de 0; 50; 100; 150 e 200 mg dm-3. O N aplicado na forma de Ca(NO3)2 apresentou melhor resultado para o solo utilizado. O crescimento das mudas de Gonçalo-Alves não foi influenciado pelas diferentes fontes de N, mas respondeu às doses. A altura da planta, o diâmetro do coleto, o teor de clorofila foliar, o peso da matéria fresca e seca da parte aérea e do sistema radicular, o peso seco total, bem como o IQD e a razão entre o peso da matéria seca da parte aérea e do sistema radicular, apresentaram valor máximo para doses que variaram de 59,0 a 72,5 mg dm-3 de N, permitindo sugerir a dose de 72,5 mg dm-3 de N como suficiente para o crescimento satisfatório de mudas de Gonçalo-Alves.

Resíduos da agroindústria de chá preto como substrato para produção de mudas de hortaliças

O objetivo do trabalho foi determinar o efeito do resíduo do chá preto como substrato na produção de mudas de alface, tomate e pepino. Para tal, foram conduzidos testes de germinação e ensaios de crescimento empregando, respectivamente, extrato aquoso e diferentes tipos de resíduo. Nos testes de germinação, sementes de alface, tomate e pepino foram colocadas em bandejas sobre papel de filtro umedecido com água ou extrato aquoso na concentração de 1, 5 e 10%. Nos ensaios de crescimento, sementes das mesmas espécies foram colocadas em bandejas contendo: 1. vermiculita; 2. resíduo decomposto mais vermiculita; 3. resíduo decomposto e 4. resíduo bruto lavado mais vermiculita. O resíduo decomposto foi obtido após processo de decomposição do resíduo bruto e o resíduo bruto lavado foi obtido a partir da lavagem do resíduo bruto em água. Nos testes de germinação e ensaios de crescimento, foi adotado o delineamento experimental inteiramente casualizado com quatro tratamentos e quatro repetições com 30 sementes cada. Os resultados indicaram que o extrato aquoso inibiu a germinação das sementes e o crescimento das plântulas de alface, tomate e penino. O uso do resíduo bruto lavado mais vermiculita reduziu a emergência das plântulas. O resíduo decomposto e o resíduo decomposto mais vermiculita estimularam a emergência e o crescimento das plântulas. O processo de decomposição tornou viável a utilização do resíduo da indústria de chá preto como substrato para produção de mudas de hortaliças.

Substratos para produção de mudas de mamoneira compostos por misturas de cinco fontes de matéria orgânica

O plantio de mamona (Ricinus communis L.) através de mudas pode ser uma alternativa para um melhor aproveitamento da curta estação chuvosa do semi-árido brasileiro, porém ainda não se dispõe de informações básicas para o emprego desta técnica. Na formulação de substratos para produção de mudas de mamona, as características físicas, principalmente a aeração, são fatores de grande importância. O presente estudo objetivou avaliar a composição de substratos utilizando misturas de solo, esterco bovino, casca de amendoim, mucilagem de sisal, bagaço de cana e cama de frango. Utilizou-se delineamento em blocos casualizados com 12 tratamentos e quatro repetições. Sementes da cultivar BRS Nordestina foram semeadas em sacos plásticos de 17 x 28cm, contendo misturas dos materiais a serem testados. Valores de altura, área foliar, número de folhas e diâmetro caulinar foram registrados semanalmente entre 15 e 43 dias após a emergência. Na última coleta também se registraram a massa seca da parte aérea e das raízes. O substrato composto por solo + casca de amendoim + cama de frango + mucilagem de sisal propiciou o melhor crescimento das mudas. A cama de frango contribuiu para o enriquecimento químico do substrato, enquanto a casca de amendoim e a mucilagem de sisal contribuíram para adequar as características físicas de aeração e retenção de água.

Volume de recipientes e composição de substratos para produção de mudas de mamoneira

A mamoneira (Ricinus communis L.)é uma oleaginosa bem adaptada ao cultivo na região semi-árida por sua rusticidade e resistência ao estresse hídrico. Seu plantio é tradicionalmente feito por sementes, mas o uso de mudas pode se tornar atraente como estratégia para melhor aproveitamento da curta estação chuvosa. Para adoção desta tecnologia, a definição de aspectos técnicos como volume de recipientes, composição do substrato e período de permanência da muda no viveiro são fundamentais para o êxito da técnica. Conduziu-se experimento em casa-de-vegetação da Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) Algodão em Campina Grande, com sementes da cultivar de mamona de porte médio BRS Nordestina, em delineamento de blocos casualizados com 4 repetições e 25 tratamentos em distribuição fatorial 5², sendo os fatores cinco volumes de recipientes e cinco composições de substratos. Entre 15 e 43 dias após a emergência (DAE) foram feitas cinco coletas destrutivas semanais para obtenção de dados de altura, diâmetro caulinar, área foliar, número de folhas e matéria seca da parte aérea e radicular. Com os dados obtidos calculou-se o tamanho da folha. Detectaram-se efeitos significativos dos tratamentos em todas as variáveis estudadas. O crescimento das mudas estabilizou-se aproximadamente aos 36 DAE, independente do volume do recipiente. Os substratos compostos por mistura de areia com esterco bovino ou casca de amendoim propiciaram o melhor crescimento das mudas, enquanto aqueles contendo bagaço de cana ou mucilagem de sisal foram os piores. Recipientes de 2 L de volume foram os mais adequados para a produção de mudas de mamoneira.

Biological activity of Gomphrena elegans Mart. Var. Elegans (Amaranthaceae)

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