180 resultados para Native plants


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日益增强的旅游活动干扰正成为九寨沟世界自然遗产的有效保护与持续管理不可回避的挑战,已成为当前区域生态保护与经济发展的焦点问题之一。阐明相关旅游的干扰活动对核心景区植物物种组成、多样性与结构的影响是九寨沟有效保护与持续管理的必要前提和基础,然而至今少有研究。选择九寨沟与旅游活动相关的九个景点、公路建设地段以及退耕地还林地,详细调查了林下植被结构、物种组成与多样性,比较了相关旅游活动干扰与基本未受干扰地段的差异。目的是阐明九寨沟核心景区旅游干扰条件下植物多样性与群落结构及其特点,揭示旅游干扰与植被结构和生物多样的相互关系,评估九寨沟旅游管理的有效性,探索减免旅游干扰影响的对策与措施。初步结论如下。 1.旅游活动引起九寨沟核心景区植物组成和群落结构特征改变显著。栈道及公路附近许多耐荫喜湿的敏感种局部消失,而早熟禾、车前草、委陵菜等耐干旱、耐践踏、繁殖能力强的植物种群扩大;外来物种频繁出现并已少量侵入干扰相对较轻的林分深处;林下群落以草本植物为优势,灌木与苔藓植物的频度、盖度、高度以及灌木密度均有所下降。可见,大量的游人活动和景区公路建设已对九寨沟丰富的乡土植物构成极大威胁,导致其生物多样性降低。而九寨沟农耕地退耕有利于九寨沟生态环境和生物多样性保护,正逐步向稳定群落演替。 2.干扰强度的差异导致九寨沟植物所受影响的程度不同。栈道附近植物受影响的程度与游人活动频率有关,活动频率高的地段干扰强度大,对植物的影响程度重,反之植物所受的影响较轻。强度干扰地段,耐荫喜湿的物种少见,伴生植物优势地位突出,生物多样性明显降低,植物群落结构特征改变也极为显著;干扰较轻的地段,伴生物种少量出现,植物群落结构变化不明显,生物多样性略为降低,部分地区结构参数值和多样性指数有所升高。公路修建是一种强度干扰,它导致附近植物种类极为单一,草本优势种异常突出,多数植物生活力低下、生长更新能力差。 3.不同植物类群受干扰影响的程度不同。草本及苔藓植物的种类组成和多样性指数受干扰影响较大,灌木和苔藓植物的结构受干扰影响较大,苔藓植物对干扰影响最为敏感。 综合分析表明,九寨沟核心景区的管理虽然比较规范,但目前核心区热点景点段的管理仍然不够,旅游活动驱动了林下植被退化明显、物种组成显著变化、生物多样性衰退、非乡土喜光耐旱种群扩大。导致九寨沟核心区旅游活动与生物多样性保护目标尖锐冲突,进一步约束旅游活动带来的干扰,强化管理,开展林下植被恢复与非乡土喜光耐旱种群调控是九寨沟自然遗产地保护一项紧迫任务。 The increasing tourism disturbance is an unavoidable challenge to effective conservation and sustained tourist management of Jiuzhaigou Nature Reserve. It has become one of the focal problems of regional ecological protect and economic development. It is important to clarify effects of tourism disturbance on plant species composition, diversity and community structure in kernel spot for effective conservation and sustained tourist management in Jiuzhaigou, China. However, there were little studies about this yet. The study investigated the vegetation structure, species composition and diversity at nine sight spot, road area and four abandoned farmlands connecting with tourism, and compared the differences between disturbed area and undisturbed area. The purpose of the this study is clarifying the plant diversity and community structure and characteristics of the disturbed area in kernel spot of Jiuzhaigou, discovering the relation between vegetation structure and biodiversity, evaluating the effect of tourist management and exploring the measure decreasing tourist disturbance. Our results are following: 1. Tourism disturbance caused a significant change in species composition and structure of plant communities in kernel Spot of Jiuzhaigou. In the vicinity of plank and road, some native shade-tolerant or hygrophilous plants had disappeared, accompanying with the population expansion of some xerophilous and disturbance-resisting species such as Poa sp. Plantago depressa, Potentiila multicaulis and some exotic and synanthropic species. Herbs were domaint species, while frequency coverage and height of shrubs and bryophytes, and shrub density decreased. In indicated that tourist activities and build of road had adversely affected on native plant species, and led to decline in biodiversity of Jiuzhaigou Nature Reserve. Abandoned farmlands maybe conduced to entironment and biodiversity conservation. 2. Nearby the plank, influency variable of tourism disturbance on plant was alosely and positively correlated with disturbance intensity. There was companion plant species and lacked shape-loving species in heavy disturbed areas, which caused decrease in biodiversity and significant change in community structure in these places. On the contrary, in the slightly disturbed areas, some companion speices displayed and biodiversity decreased slightly, but no significant change in community structure in these areas. The biuld of road is a heavy disturbance form, which led to increase of herb species and to decrease in vitality and regeneration capacity. 3. The intensity of tourism disturbance on plant depended on plant groups. Tourism interference significantly influenced species composition and diversity index of herb and bryophyte; it also significantly influenced community structure; the bryophyte was more sensitive to tourism disturbance. Our result indicated that the management in kernel spot of Jiuzhaigou is relatively reasonable, but not adequate. Tourism speed the degradation of the vegetation under woodland, the change of the species composition, the decreaing of the biodiversity and the expanding of the exotic sunloving plant populations. The contradiction between tourism and conserving biodiversity is increasing, so enforcing management, regenerating the vegetation under woodland and adjusting the exotic sunloving arid-tolerent plant populations is a pressing work to protect the Jiuzhaigou natural legacy.

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植物群落及其环境在干扰后的演替格局和过程的研究,是群落和生态系统动态研究的一个热点。选取青藏高原东缘山原区川西云杉林皆伐后,从草地过渡到灌丛的关键阶段的4 个皆伐迹地(恢复时间为8 a、10 a、16 a 和21 a),研究皆伐及自然恢复过程对林下典型灌木银露梅(Potentilla glabra)和唐古特忍冬(Lonicera tangutica)的生长与繁殖能力的影响以及灌木植物在迹地上的更新情况,分析灌木在不同生境中的适应对策和适应能力的差异,为揭示青藏高原东缘山原区迹地植被从草甸到灌丛演替的过程和特点及促进迹地演替与植被恢复进程提供理论依据和技术支撑。研究主要结论如下:1)皆伐后银露梅生长和繁殖能力显著提高,但对唐古特忍冬的影响不明显。皆伐后银露梅丛基径、高度和各部分生物量都显著增加(P < 0.05),但唐古特忍冬只有叶生物量和地下生物量增加,总生物量和其余构件生物量无显著变化。皆伐后,银露梅的结实数量、结实株数、不结实株数和结实株/不结实株比例显著增加(P < 0.05)。自然恢复过程中,银露梅和唐古特忍冬生长能力以及银露梅的结实量都表现出降低的趋势。随着迹地自然恢复时间的增加,银露梅和唐古特忍冬的基径、高度、丛叶片数和各部分生物量有减少的趋势。银露梅的结实株数增加, 但结实数量减少。2)皆伐对银露梅和唐古特忍冬生物量分配模式影响不一致。原始林和迹地中(除CT85)银露梅的生物量大小关系皆为:地下>茎>侧枝>叶。唐古特忍冬在原始林中的生物量大小关系为:茎>地下部分>侧枝>叶,而皆伐后生物量的分配情况改变,生物量大小关系变为:地下部分>茎>侧枝>叶。随着自然恢复时间的增加,银露梅减少了地下生物量的分配,而唐古特忍冬增加了地下生物量的分配。3)皆伐和恢复时间的增加改变了迹地物种组成,促使阳性乔、灌木在迹地上定居。4 个迹地上共出现了灌木15 种,乔木3 种,没有出现天然云杉和冷杉幼苗。随着恢复时间的增加,迹地上的灌木物种由原始林下的耐阴物种逐步发展为以针刺悬钩子(Rubus pungens)为主的阳性灌木。4)影响灌木幼苗密度和幼树密度的因子不一致。灌木幼苗密度与灌木层盖度显著负相关,与苔藓层盖度显著正相关。幼树密度与草本层盖度正相关,与苔藓层盖度、灌木层盖度和高度负相关。5)研究发现在青藏高原东缘山原区皆伐15~20 a 后,迹地仍以草本植物为主,推测皆伐后至少20 a 以上迹地才可能向灌丛阶段过渡,比高山峡谷地区的演替进程至少推迟了20 a。银露梅和唐古特忍冬在皆伐后自然恢复过程中表现出不同的生长与繁殖策略是由两个物种的生物学特性的差异引起的。银露梅比唐古特忍冬更适应迹地退化环境。促进青藏高原东缘山原林区迹地森林恢复一方面是尽量减少人为活动的破坏,另一方面,可以通过在迹地中播种适当的乡土乔、灌木种子(如白桦、银露梅)等人工措施,以加快演替进程。The succession pattern and process of plant community and their environments is a hot spotin community and ecosystem dynamic study. Four clearcuts were chosen in Rangtang(recovery time of 8 a、10 a、16 a and 21 a), which represented the key stage of thecommunity evolved from grass stage to shrub stage in the eastern margin of theQinghai-Tibetan Plateau. The growth and reproduction of the Potentilla glabra andLonicera tangutica and the natural regeneration of shrub plants in the primary Piceabalfouriana forest and 4 clearcuts were studied to explore how clear cutting andnatural recovery process affected the understory shrub species during the 21 years inthe eastern margin of the Qinghai-Tibetan Plateau. The main results were below.1) The growth and reproduction of P. glabra significantly increased after forestclear cutting.. But it was not so significant as to the L. tangutica. The organismbiomass and total biomass of P. glabra were increased obviously after clear cutting(P< 0.05). But only leaves and underground biomass of L. tangutica increasedsignificantly after clear cutting(P < 0.05). The number of fruit and growth of P. glabraincreased significantly after clear cutting too(P < 0.05). The ramet height, basaldiameter , organism biomass and friut number of P. glabra and L. tangutica reducedas the increase of recovery time.2) The biomass allocation patterns varied between P. glabra and L. tangutica inthe primary forest and clearcuts. The biomass allocation of P. glabra both in primary forest and clearcuts was followed as: underground part > stem > branch > leaves.However, the biomass allocation of L. tangutica had changed after the clear cutting.The biomass allocation of L. tangutica in the primary forest was followed as: stem >underground part > branch > leaves and it was underground part > stem > branch >leave in clearcuts. The biomass allocation of P. glabra and L. tangutica varied amongclearcuts. Aboveground biomass was increased while underground biomass decreasedfor P. glabra with the increase of recovery period. However, the L. tangutica showedthe reverse changing pattern.3) Clear cutting and recovery time had changed the species composition of theclearcuts. There were 15.shruby species and 3 tree species in the four clearcuts. Nospruce and fir seedlings were found. In the early stage after clear cutting, there wereonly understory shrub species from the primary Picea balfouriana forest. The sunnyspecies, especieally Rubus pungens invaded intensly as the increase of recovery time.4) There was a significant negative relationship between density of seedlingswith shrub layer coverage and positive correlation with moss coverage. The saplingshad significantly positive correlation with herb layer coverage and negativecorrelation with moss coverage, shrub layer coverage and height.5)Comparing to studies in Miyalou, a nearby high mountain and canyon area,the secondary sucession in this subalpine plateau areas lagged at least 20 years.P. glabra and L. tangutica showed different growth and reproduction strategies toclear cutting and natural recovery , which may associated with the difference of theirbiological characters. P. glabra was more adaptive to the clear cutting than the L.tangutica. Two suggestions were probably recommended to promote the recoveryprogress in the subalpine plateau areas based on the results of this study. Limitanthropogenic disturbance, and meanwhile sow native tree and shrub seeds inclearcuts.

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繁殖更新是植物生活史的重要阶段,在退化生态系统中,植物繁殖更新能力往往较差,是植被恢复的限制环节,因而也成为恢复研究重点和核心。本研究选择岷江干旱河谷广泛分布的三种蔷薇:多苞蔷薇(R. multibracteata)、黄蔷薇(R. hugonis)和川滇蔷薇(R. soulieana)为研究对象,通过野外调查,在查明其生长、繁殖更新状况的基础上,采用控制和模拟实验,对种子和幼苗阶段进行了深入研究,综合分析更新潜力,并提出相对应的促进更新和植被恢复措施。主要结论如下: 1)三种蔷薇在岷江干旱河谷广泛分布,生长和繁殖状况良好,结实量大。各生长指标:株高、基径和冠幅,繁殖指标:结实数量、重量和单果重量都具有显著的空间差异性。基径对多苞蔷薇结实量影响最大;而冠幅对黄蔷薇结实量影响最大。海拔和纬度是对蔷薇生长和繁殖影响最大的环境因素,随着海拔和纬度的升高,植株生长更高大,结实量增加;坡度和坡向对其生长和繁殖也有一定影响,随着坡度 和坡向增加,蔷薇生长和结实受到抑制。 2)三种蔷薇在岷江干旱河谷更新现状不佳, 但更新潜力大。活力种子比率低,动物取食以及两年生幼苗的大量死亡是蔷薇更新的主要限制因素。多苞蔷薇和黄蔷薇的结实率低,川滇蔷薇较高。三种蔷薇种子产量大,但种子质量较差,更新具有充足的种源。三种蔷薇都能形成持久种子库,种子库中种子总量大,但有效种子少,黄蔷薇被动物啃食的比例很高,多苞蔷薇和川滇蔷薇也有一部分种子受到动物破坏。三种蔷薇幼苗库组成特征表现为,当年生幼苗所占比例很高,年龄较大幼苗所占比例小。 3)三种蔷薇都具有不同程度休眠,未经处理种子的发芽率极低。黄蔷薇休眠程度最深,为深度生理休眠;多苞蔷薇为中度生理休眠;川滇蔷薇为非深度生理休眠。三种蔷薇种子在形态上发育成熟,种皮具有透水性。蔷薇果果肉和瘦果中含有抑制物质,其浸泡液抑制了油菜种子萌发,果肉抑制作用更强,果肉和瘦果浸泡液的抑制程度分别为:川滇蔷薇>黄蔷薇>多苞蔷薇。切割和硫酸腐蚀提高了川滇蔷薇种子的发芽能力,而对多苞蔷薇和黄蔷薇没有影响。完全去除瘦果果皮和种皮提高了多苞蔷薇种子发芽率,但对黄蔷薇没有影响。赤霉素和烟水对蔷薇种子萌发没有促进作用。三种蔷薇打破休眠所需低温层积时间分别为:黄蔷薇>多苞蔷薇>川滇蔷薇。对于多苞蔷薇和川滇蔷薇,层积前对种子进行硫酸腐蚀或暖温层积能缩短低温层积时间,提高发芽率。对于多苞蔷薇,变温层积中暖温层积和低温层积具有一定的负补性,即延长暖温层积可以缩短种子萌发对低温层积的需要。 4)多苞蔷薇种子形态特征和种子休眠与萌发在不同海拔梯度间存在较大差异。种子采集时间、采集季节和干藏影响多苞蔷薇和川滇蔷薇的种子休眠。多苞蔷薇果实大小、种子大小和千粒重、种皮厚度随海拔升高而增加,而种子饱满率和活力随海拔升高而降低,种子休眠程度也随海拔升高而增加。种皮厚度与种子大小、千粒重成正相关关系,硫酸腐蚀后的种子经过不同时间的低温层积后,种子发芽率与种皮厚度、种子大小、千粒重、海拔成正相关关系。2006 年采集川滇蔷薇和多苞蔷薇种子休眠程度较2005 年低。种子休眠随种子年龄增加而减弱。高温和干旱能减轻多苞蔷薇和川滇蔷薇种子休眠。 5)三种蔷薇的生长和生物量积累在干旱胁迫条件下受到抑制,而生物量分配、叶片形态特征和水分利用特征等都发生了变化。三种蔷薇的根、茎、叶各器官生物量以及总生物量等在干旱胁迫下明显减小,叶片脱落数量增加。在干旱胁迫条件下,较多的生物量分配到地下部分,从而这使R/S 明显增加。比叶面积(SLA)和冠层面积比(LAR)对干旱胁迫的反应不敏感,仅有部分物种在干旱胁迫条件下发生了变化,并且其变化特点在不同年龄幼苗之间有一定差异。干旱胁迫对WUE 的影响在不同物种间存在差异。多苞蔷薇和黄蔷薇的WUE 随着干旱胁迫的增加而增大, 而川滇蔷薇的WUE 则随干旱胁迫增加而减小。在干旱胁迫条件下,多苞蔷薇和黄蔷薇叶片脱落量和生物量减小幅度较川滇蔷薇大,表明其抗旱能力较强。在干旱胁迫条件,三种蔷薇两年生幼苗的生物量减小幅度较当年生幼苗小,表明两年生幼苗的抗旱能力更强。 6)两种植被恢复措施中,幼苗移栽比播种具有更好的植被恢复效果。播种后,蔷薇种子的发芽率较高,但出苗率都很低,即使出苗,幼苗也几乎在一月内全部死亡。 三种微生境条件下(灌木、半灌木和裸地),种子出苗和幼苗成活没有差异。移栽幼苗总体死亡率都比较低,小于20%。特别是两年生幼苗死亡率更低,小于2%。移栽后的幼苗生长状况良好,在整个生长季中,各生长指标不断增加。生境对幼苗的存活率没有显著影响,但对于幼苗的生长和生物量积累有一定影响,裸地更有利于幼苗生长和生物量积累。与当年生幼苗相比,两年生幼苗具有更高的成活率。总之,三种蔷薇在干旱河谷分布广泛、生长繁殖状况良好,结实量大,具有丰富种源,繁殖更新潜力大,但繁殖更新状况不佳;种子散布后动物对种子的取食、种子的深度休眠过程、种子出苗以及当年生幼苗的存活和定居是更新的主要限制环节。水分是影响结实、种子休眠解除和萌发,幼苗存活和定居的最主要的限制因素。在植被恢复中,应在种子成熟季节大量采集种子,在室内打破休眠后进行人工播种,培育两年生幼苗,通过幼苗移栽方式进行植被恢复。川滇蔷薇应栽种在相对湿润的过渡区,而多苞蔷薇和黄蔷薇可以应用于核心区植被恢复。 Regeneration is an important phase in plant life cycle. It has been a key component of ecological restoration in degradation ecosystem in which plants commonly has poor regeneration. In this paper, we investigated the natural growth, propagation and regeneration status of native three rose species, Rosa multibracteata, R. hugonis and R. soulieana, and analysis the limitation in seed germination and seedling establishment stages. Advice on facilitating the use of these plants in restoration based on the results has been proposed. The results were as follows: 1) Three rose plants widely distributed in the dry valley of the Minjiang River, and made a good performance in growth and propagation. There were significant spatial differences in each growth parameter, such as ramet height, basal diameter, crown diameter and propagation parameters including hip number of a clump, hip mass of a clump and a hip mass. Basa diameter was the most important growth parameter influencing fruit number for R. multibracteata and crown diameter was for R. hugoni. Altitude and latitude had the greatest effect on the growth and propagation of rose plants among environmental conditions. Each parameter of growth and propagation increased with the increase of altitude and latitude. In addition, the increase of slope and aspect limited the growth and propagation. 2) Three rose plants had poor natural regeneration, but great regeneration potential. Low seed viability, predation and higher mortality of current year old seedlings were the limitation in regeneration. R. multibracteata and R. hugonis had higher fruiting rates than R. souliean. All three plants produced a great number of seeds, while their viability was poor. Three rose plants had persistent seed banks, with high total seed number but very low viable seed density. Predation was most severe in R. hugonis, and it also existed to some degree in R. multibracteata and R. soulieana. The seedling age-structure was characteristic of current-year seedlings predominating and few older seedlings were observed. 3) Three rose seeds were dormant and untreated seeds germinated with very low germination percentages. The rose seeds had morphological mature embryos, and achenes were permeable. Some inhabit substances existed in hips and achenes for the extracts of hips and achenes inhibited germination of Brassica campestris. The inhibition effect of the extracts of three rose hip and achenes was R. soulieana>R. hugonis>R. multibracteata. Mechanical and H2SO4 scarification increased R. soulieana germination but had no effect on germination of R. hugonis and R. multibracteata seeds. Full removal of pericarp and testa improved the germination of R. multibracteata but did not affect R. hugonis germination. GA3 and smoke water had no positive effect on rose seed germination. The periods of cold stratification required to released seed dormancy was R. hugonis > R. soulieana >R. multibracteata. H2SO4 scarification and warm stratification shortened cold stratification to release dormancy for R. soulieana and R. multibracteata. Warm stratification had complementary effect for cold stratification, i.e. the longer warm stratification seeds received, the shorter cold stratification were required to obtain the same germination percentage. Three rose seeds had different kinds of dormancy; R. hugonis has deep physiological dormancy, R. multibracteata with intermediate physiological dormancy and R. souliean non-deep physiological dormancy. 4)The seeds traits and dormancy of R. multibracteata showed significant difference across altitudes. Year and season of seed collection had significant effect on seed dormancy for both R. souliean and R. multibracteata. Hip size, seed size, seed weight, seed coat thickness and seed dormancy level increased with the increase of the altitude. There were positive relations between seed coat thickness with seed size and seed weight. Germination percentage of seeds treated with H2SO4 scarification following different periods of cold stratification showed positive relation with seed coat thickness, seed size, seed weight and altitude. Seeds of R. souliean and R. multibracteata collected in 2006 had low dormancy level than those collected in 2005. Seed dormancy decreased with increasing seeds age. High temperature and drought were associated with low dormancy level. 5) Seedling growth, the total dry mass and their components of seedlings were reduced, while leaf senescence accelerated under drought stress. More biomass allocation to root system resulted in higher R/S ratio under drought. Water-use efficiency (WUE) of R. multibracteata and R. hugonis increased, while it declined for R. soulieana under drought stress. R. soulieana seedlings had poor drought-resistance capacity it had more senescent leaves, and its reduction of biomass was stronger than two other rose plants under drought. The reduction degree of one year old seedlings under drought stress was slighter than that of current year seedlings. Therefore, one year old seedling was more drought-resistent compared to current year seedlings. 6)Planting seedlings may have better effect in comparison with direct seeding. Most seeds germinated after seeding, but seedling emergence was very low. More than 80 % seedlings from direct seeding died within a months after emergence. Seedling emergence and survival rate did not show difference among microhabitats. Mortality rates of seedlings artificially planted in microhabitats were general lower than 20 %, and the mortality rate of one year old seedlings was lower than 2 %. Each grow parameter including plant height, leaf number and branch number continually increased after planting. Microhabitat type had effect on the growth parameter and biomass production, but it did not influence the seedling survival. Bare land tended to facilitate seedling growth. One year old seedlings had higher survival rate than current year seedlings. In conculsion, the three rose had wide distribution in the dry valley of the Minjiang River. They produced many seeds and had tolerance to drought stress to some degree. But they had poor regeneration in habitats may be caused by predation, seed dormancy,and high mortality in current year seedlings. We recommend that rose plants should be utilized in restoration by planting two-year old seedlings in spring. A large quantity of seeds should be collected artificially in autumn, release seed dormancy in room, and then cultivate two-year old seedlings by seeding in particular container. R. soulieana seedling probably be planted in transition area, and R. multibracteata and R. hugonis can be used in core area of the dry valley of the Minjiang River.

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株高是农作物的重要农艺性状之一,适度矮化有利于农作物的耐肥、抗倒、高产等。20世纪50年代,以日本的赤小麦为矮源的半矮秆小麦的培育和推广,使得世界粮食产量显著增长,被誉为“绿色革命”。迄今为止,已报到的麦类矮秆、半矮秆基因已达70多个,但由于某些矮源极度矮化或者矮化的同时伴随不利的农艺性状,使得真正运用于育种实践的矮源较少。因此,发掘和鉴定新的控制麦类作物株高的基因,开展株高基因定位、克隆及作用机理等方面的研究,对实现麦类作物株高的定向改良,具有重要的理论意义和应用价值。簇毛麦(Dasypyrum villosum,2n=14,VV)是禾本科簇毛麦属一年生二倍体异花授粉植物,为栽培小麦的近缘属。本课题组在不同来源的簇毛麦杂交后代中发现了一株自然突变产生的矮秆突变体。观察分析了该突变体的生物学特性,对矮秆性状进行了遗传分析,对茎节细胞长度、花粉的活力进行了细胞学观察,考察了该突变体内源赤霉素含量及不同浓度外施赤霉素对突变体的作用,分析了赤霉素生物合成途径中的内根贝壳杉烯氧化酶(KO)和赤霉素20氧化酶(GA20ox)的转录水平,对赤霉素20氧化酶和赤霉素3-β羟化酶(GA3ox)进行了克隆和序列分析,并对GA20ox进行了原核表达和表达的组织特异性研究。主要研究结果如下:1. 该突变体与对照植株在苗期无差异,在拔节后期才表现出植株矮小,相对对照植株,节间伸长明显受到抑制,叶鞘长度基本不变。在成熟期,对照植株的平均株高为110cm,而突变株的平均株高为32cm,仅为对照植株的1/3 左右。除了株高变矮以外,在成熟后期,突变株还表现一定程度的早衰和雄性不育。I2-KI染色法观察花粉活力结果表明,对照植株花粉90%以上都是有活力的,而突变植株的花粉仅20%左右有活力。2. 突变株与对照植株的杂交F1代均表现正常株高,表明该突变性状为隐性突变。F1代植株相互授粉得到的168株F2代植株中,株高出现分离,正常株高(株高高于80cm)与矮秆植株(株高矮于40cm)的株数比为130:38,经卡方检验,其分离比符合3:1的分离比,因此推测该突变体属于单基因的隐性突变。3. 用ELISA方法检测突变株和对照植株的幼嫩种子中内源性生物活性赤霉素(GA1+3)含量,结果表明突变株的赤霉素含量为36 ng/ml,而对照植株的赤霉素含量为900 ng/ml。对突变株外施赤霉素,发现矮秆突变株的株高和花粉育性均可得到恢复。这些结果表明该突变株为赤霉素缺陷型突变。4. 用荧光定量PCR方法比较突变株与对照植株中内根贝壳杉烯氧化酶和赤霉素20氧化酶的转录水平,结果表明突变株的KO转录水平比对照植株分别提高了6倍(苗期)和16倍(成熟期),突变株的GA20ox转录水平与对照植株在苗期无明显差异,在成熟期突变株较对照植株则提高了10倍左右。这些结果表明该矮秆突变体与赤霉素的生物合成途径密切相关,而且极有可能在赤霉素的生物合成途径早期就发生了改变。5. 以簇毛麦总基因组为模板,同源克隆了GenBank登录号为EU142950,RT-PCR分离克隆了簇毛麦的GA3ox基因cDNA全长序列,分析结果表明该cDNA全长1206bp,含完整编码区1104bp,推测该序列编码蛋白含368个氨基酸残基,分子量为40.063KD,等电点为6.27。预测的氨基酸序列含有双加氧酶的活性结构,在酶活性中心2个Fe离子结合的氨基酸残基非常保守。该序列与小麦、大麦和水稻的GA3ox基因一致性分别为98%、96%、86%。基因组序列与cDNA序列在外显子部分一致,在478-715bp和879-1019bp处分别含238bp和140bp的内含子。6. 通过RT-PCR技术克隆了簇毛麦的GA20ox基因全长,命名为DvGA20ox,GenBank登录号为EU142949。该基因全长1080个碱基,编码359个氨基酸,具有典型的植物GA20ox基因结构。该基因编码的蛋白质与小麦、大麦、黑麦草等GA20ox蛋白的同源性分别为98%,97% 和91%。该序列重组到原核表达载体pET-32a(+)上,将获得的重组子pET-32a(+)-DvGA20ox转化大肠杆菌BL21pLysS后用IPTG进行诱导表达。SDS-PAGE分析表明,DvGA20ox基因在大肠杆菌中获得了高效表达,融合蛋白分子量为55kDa。定量PCR分析表明,该基因在簇毛麦不同器官中的表达差异明显:叶片中表达水平最高,根部表达水平次之,茎部和穗中表达较弱。在外施赤霉素后,该基因的表达水平在两小时以后急剧下降,表明该基因的表达受自身的反馈调节。本研究结果认为,(1)该簇毛麦矮秆突变体为单基因的隐性突变;(2)该矮秆突变体为赤霉素敏感突变,内源赤霉素含量检测表明突变体的内源性赤霉素含量仅为对照植株的1/30;(3)荧光定量PCR结果表明突变株的赤霉素生物合成途径的关键酶基因表达水平比对照植株高,而且突变植株的赤霉素生物合成改变很可能发生在赤霉素生物合成途径的早期;(4)GA20ox有表达的组织特异性,且受到自身产物的反馈调节。 Plant height is an impotrant agronomic trait of triticeae crops.Semi-dwarf cropcultivars, including those of wheat, maize and rice, have significantly increased grainproduction that has been known as “green revolution”. The new dwarf varieties couldraise the harvest Index at the expense of straw biomass, and, at the sametime, improvelodging resistance and responsiveness to nitrogen fertilizer. Moreover, dwarf traits ofplant are crucial for elucidating mechanisms for plant growth and development aswell. In many plant species, various dwarf mutants have been isolated and theirmodles of inheritance and physiology also have been widely investigated.The causesfor their dwarf phenotypes were found to be associated with plant hormones,especially, gibberellins GAs.Dasypyrum villosum Candargy (syn.Haynaldia villosa) is a cross-pollinating,diploid (2n = 2x = 14) annual species that belongs to the tribe Triticeae. It is native toSouthern Europe and West Asia, especially the Caucasuses, and grows underconditions unfavorable to most cultivated crops. The genome of D. villosum,designated V by Sears, is considered an important donor of genes to wheat for improving powdery mildew resistance, take-all, eyespot, and plant and seed storageprotein content. A spontaneous dwarf mutant was found in D. villosum populations.The biological character and modles of inheritance of this dwarf mutant are studied.The cell length of stem cell is observed. The influence of extraneous gibberellin tothe dwarf mutant is also examined; the transcript level of key enzyme of gibberellinbiosynthesis pathway in mutant and control plants is compared. GA3ox and GA20oxare cloned and its expression pattern is researched.1. The dwarf mutant showed no difference with control plants at seedlingstage.At mature stage, the average height of control plants were 110cm and the dwarfplants were 33cm. The height of the mutant plant was only one third of the normalplants due to the shortened internodes. Cytology observation showed that theelongation of stem epidermal and the parenchyma cells were reduced. The dwarfmutant also shows partly male sterile. Pollen viability test indicates that more than80% of the pollen of the mutant is not viable.2. The inheritance modle of this dwarf mutant is studied. All The F1 plantsshowed normal phenotype indicating that the dwarfism is controlled by recessivealleles. Among the 168 F2 plants, there are 130 normal plants and 30 dwarf plants, thesegregation proportion accord with Mendel’s 3:1 segregation. We therefore proposethat this dwarf phenotype is controlled by a single recessive gene.3. Quantitative analyses of endogenous GA1+3 in the young seeds indicated thatthe content of GA1+3 was 36ng/ml in mutant plants and 900ng/ml in normal plants.The endogenous bioactive GA1+3 in mutant plants are only about 1/30 of that innormal plants. In addition, exogenously supplied GA3 could considerably restore themutant plant to normal phenotype. These results showed that this mutant wasdefective in the GA biosynthesis.4. More than ten enzymes are involved in GA biosynthesis. KO catalyzes thefirst cytochrome P450-mediated step in the gibberellin biosynthetic pathway and themutant of KO lead to a gibberellin-responsive dwarf mutant. GA20ox catalyze therate-limited steps so that their transcript level will influence the endogenous GAbiosynthesis and modifies plant architecture. The relative expression levels of genesencoding KO and GA20ox were quantified by real time PCR to assess whether thechanges in GA content correlated with the expression of GA metabolism genes andwhere the mutant occurred during the GA biosynthesis pathway. In mutant plants,the transcript levels of KO increased about 6-fold and 16-fold at the seedling stage and elongating stage respectively comparing with the normal plants. For theseedlings, there was no notable difference in the expression of GA20ox betweenmutant and normal plants. At the elongating stage, GA20ox transcript increased 10times in mutant plants, suggesting that the GA biosynthesis pathway in mutant plantshad changed from the early steps rather than the late steps.5. A full length cDNA of D. villosum gibberellin 3β-hydroxylase homology(designated as DvGA3ox) was isolated and consisted of 1206bp containing an openreading frame of 1104bp encoding 368 predicted amino acid residues. Identityanalysis showed that the gibberellin 3β-hydroxylase nucleotide sequence shared 98%,96% and 86% homology with that of wheat, barley and rice. The predicted peptidecontained the active-site Fe of known gibberellin 3β-hydroxylase and the regionhomologous to wheat, barley and Arabidopsis. The genomic clone of gibberellin3β-hydroxylase has two introns.6. The full-length cDNA of D. villosum gibberellin 20 oxidase (designated asDvGA20ox) was isolated and consisted of 1080-bp and encoded 359 amino acidresidues with a calculated mol wt of 42.46 KD. Comparative and bio-informaticsanalyses revealed that DvGA20ox had close similarity with GA20ox from otherspecies and contained a conserved LPWKET and NYYPXCQKP regions. Tissueexpression pattern analysis revealed DvGA20ox expressed in all the tissues that wereexamined and the highest expression of DvGA20ox in expanding leaves followed byroots. Heterologous expression of this cDNA clone in Escherichia coli gave a fusionprotein that about 55KD. Transcript levels of DvGA20ox dramatically reduced twohours after application of biologically active GA3, suggesting that the biosynthesis ofthis enzymes might be under feedback control.

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在黄土丘陵区,地形因素和土壤水分是决定草地景观格局的主要因素,同时草地景观格局在不同尺度上影响着景观中的流。地形因素、土壤水分和草地结构在不同尺度上有着密切的联系,研究它们之间的关系对于了解生态系统的过程十分重要。针对黄土高原异质化的草地群落结构,选取黄土丘陵区经过20多年自然封育形成的天然草地,从坡面尺度对景观格局进行了调查研究,在地形因素、土壤水分和草地结构中选取了有代表性的指标14个,用多元统计分析对选取的指标进行了主成分分析和聚类分析。聚类分析将样方分成3种植被类型,不同植被类型的海拔、坡度、20~140cm土壤含水量以及物种丰富度和生物多样性存在显著性差异。相关分析表明:海拔对0~300cm土壤含水量影响显著;海拔对草地群落盖度,坡位、坡向对草地群落的物种丰富度和生物多样性有着重要影响;而草地群落的物种丰富度和生物多样性与0~100cm土层的含水量关系密切。