Summer Warming Limited Bud Output Drives a Decline in Daughter Shoot Biomass through Reduced Photosynthetis of Parent Shoots in Leymus chinensis Seedlings

Understanding how summer warming influences the parent and daughter shoot production in a perennial clonal grass is vital for comprehending the response of grassland productivity to global warming.Here,we conducted a simulated experiment using potted Leymus chinensis,to study the relationship between the photosynthetic activ-ity of parent shoots and the production of daughter shoots under a whole(90 days)summer warming scenario(+3°C).The results showed that the biomass of parents and buds decreased by 25.52%and 33.45%,respectively,under warming conditions.The reduction in parent shoot biomass due to warming directly resulted from decreased leaf area(18.03%),chlorophyll a(18.27%),chlorophyll b(29.21%)content,as well as a reduction in net photosynthetic rate(7.32%)and the maximum quantum efficiency of photosystem II(PSII)photochemistry(4.29%).The decline in daughter shoot biomass was linked to a decrease in daughter shoot number(33.33%)by warming.However,the number of belowground buds increased by 46.43%.The results indicated that long-term summer warming reduces biomass accumulation in parent shoot by increasing both limitation of stoma and non-stoma.Consequently,the parent shoot allocates relatively more biomass to the belowground organs to maintain the survival and growth of buds.Overall,buds,as a potential aboveground population,could remedy for the cur-rent loss of parent shoot density by increasing the number of future daughter shoots if summer warming subsides.

AFLP Variation Analysis on the Germplasm Resources of Leymus chinensis

The fingerprints of 27 Leymus chinensis (Trin.) Tzvel accessions from different regions in China were generated and their genomic DNA variations were assayed via amplified fragment length polymorphism (AFLP). A total of 537 DNA fragments were amplified ranging from 75-530 bp using 8 AFLP primer combinations, among which 89 (16.6%) were monomorphic and 329 (61.3%) were polymorphic. The average number of DNA band produced by each primer combination was 66.13 and the total polymorphic rate was 78.84%. PICs (polymorphic information contents) scores for AFLP ranged from 0.0-0.5 and the mean PIC was 0.216. PIC scores were maximum (0.5) for 8.5% of the AFLP markers. All the results revealed that there was rich polymorphism in genomic DNA of L. chinensis . A DNA molecular dendrogram was established for 27 L. chinensis genotypes based on genetic variation and UPGMA cluster analysis of 537 AFLP markers amplified by 8 primer combination, suggesting that the genetic variation with high frequency showed close correlation with their ecotopes and geographical distributions. Twenty_seven L. chinensis genotypes could be divided into four groups. Among them the lower genetic relationship was shown. The reason of high genetic variation frequency in L. chinensis species and formation of varieties was discussed.

羊草(Leymus chinensis)与灰色赖草(Leymus cinereus)及其杂交种(F_1)的抗旱生理特性比较

用不同浓度的聚乙二醇(PEG6000)进行根际水分胁迫处理,研究羊草(Leymuschinensis)、灰色赖草(Leymuscinereus)及其杂交种的抗旱生理特性。结果表明,在15%PEG、25%PEG、35%PEG不同处理下,两亲本及其杂交种叶片相对含水量(RWC)逐渐降低;相对电导率、丙二醛含量(MDA)逐渐增加;超氧化物歧化酶活性(SOD)在15%PEG、25%PEG处理下,活性逐渐增加,在35%PEG处理下,活性开始下降。而且在15%PEG、25%PEG处理下,杂交种的抗旱(耐旱)性与亲本羊草相近,明显大于另一亲本灰色赖草。

Molecular Cloning and Sequence Analysis of Class Ⅱ Chitinase Gene in Leymus chinensis

[ Objective] The aim of this study was to clone Class Ⅱ chitinase gene in Leymus chinensis grown in saline land in Heilongjiang Province and analyze its sequence, which provided a foundation for further study on the biological function and application of chitinasa gene. [ Method] cDNA library of Leymus chinensis leaves were constructed, and its DNA sequence was determined or analyzed, while the homology of chitinasa gene and amino acid sequence was compared with that in GenBank. [ Result] One full length cDNA fragment with length of 996 bp was cloned from cDNA library of Leymus chinensis leaves. The length of ORF was 768 bp encoding 225 amino acids （GenBank accession number： EU344908）. The encoding products lacked CBD and C-terminal extension region from the view of structure, but had structural characters of Class Ⅱ chitinase gene, which indicated that amino acid sequence had high homology compared with Class Ⅱ chitinase gene of rye and wheat. The constructed recombinant vector pQE-LcChi2 could express a protein of 27 kD through induction, which was consistent with the deduced encoding product of pQE-LcChi2 gene. [ Conclusion] LcChl2 gene is an expression gene, which can express in E. coll.

刈割对典型草原地带羊草(Leymus chinensis)的影响

经过１１年不同时期刈割和不同轮割研究结果表明：在羊草的抽穗期（６月２３日）、开花期（７月８日）、结实期（８月２日）、结实后期（８月１６日）和果后营养期（９月１２日）刈割，对羊草在群落地上生物量中所占的比例、羊草生物量、密度、高度均产生不同程度的影响，总的趋势是波动式地下降．随着刈割时间的后移，羊草生物量的分层结构呈现叶量上移，而茎量下移，对割草有利；它的Ｎ、Ｐ含量逐渐下降，在生长旺盛期Ｋ的含量增加，至后期下降．一年割两次（６月２３日和９月１２日）、一年割一次、割二年休一年、割一年休一年和对照（均为８月１６日）５个处理，羊草在群落生物量中所占的比例、羊草生物量、密度、高度均随刈割次数的增多而有不同程度下降，并有一定的相关关系．羊草生物量的分层结构，随刈割次数的增多而层次减少．羊草Ｎ、Ｐ的含量有随刈割次数增多而增加的趋势，Ｋ的含量有一定的波动．

Variation of Water-Use Efficiency of Leymus chinensis and Cleistogenes squarrosa in Different Plant Communities in Xilin River Basin, Nei Mongol

Water is usually considered to be a key limiting factor for the growth and reproduction of steppe plants in the Xilin River Basin, Nei Mongol. Foliar delta C-13 values, an indicator of long-term intercellular carbon dioxide concentration and thus of water-use efficiency (WUE) in plants, were measured on Leymus chinensis (Trin.) Tzvel. and Cleistogenes squarrosa (Trin.) Keng. in six communities of different habitats in die Xilin River Basin. The foliar delta C-13 values of both species tended to increase with decreasing soil water content (SWC) and a significant negative correlation was found between foliar delta C-13 Values and SWC in different soil layers, indicating that the two species could change WUE according to water availability. We also found relatively constant leaf water contents (LWC) of the two species in different habitats. Our results implied that the two steppe species might have adapted to different soil water regimes either through adjusting stomatal conductance to get a proper WUE, or through enhancing the osmosis-regulating ability to keep a relatively stable LWC. Our findings could partially explain why the two plant species have a wide distribution range and become dominant in the Xilin River Basin.

呼伦贝尔草原羊草(Leymus chinensis)光合速率的季节变化--以鄂温克旗牧业气象试验站为例

利用2005年和2006年5～9月对内蒙古呼伦贝尔草原鄂温克旗牧业气象试验站所在地羊草光合速率的系统观测数据,分析了羊草光合速率的季节变化和年际差异,及其与气象因子和土壤水分状况的关系。结果表明:(1)在整个生长季节内,羊草光合速率的变化大致呈三峰二谷的形式,峰值分别出现在返青期之后、夏季降水高峰期和秋季降水回升期。2005年光合速率的峰值明显大于2006年,前者夏季峰值的持续时间也明显长于后者,这与该年降水量较多、相对湿度和土壤含水率较高有关。(2)羊草的光合速率与测量当日前3～8d的累计降水量均呈显著正相关关系,2005年与测量当日前6d累计降水量的相关最显著,2006年与测量当日前3d累计降水量的相关最显著。与此相似,羊草光合速率与各层土壤含水率亦呈正相关关系,且2005年的相关程度一般明显优于2006年,其中,与0～20cm土壤含水率的相关系数最大,表明羊草光合速率主要受到20cm以上土壤水分的影响。(3)在水分条件较好、气温偏低的2005年,羊草光合速率与日平均气温之间呈微弱负相关关系,与相对湿度之间呈显著正相关关系,表明在水热组合满足羊草生长需要的情况下,相对湿度通过增加或降低气孔导度对光合速率产生显著的影响,而气温对光合速率的影响不大。在水分条件较差、气温偏高的2006年,羊草光合速率与日平均气温之间呈显著负相关关系,与相对湿度之间呈不显著正相关关系,这与水热组合失衡情况下气温升高加剧蒸发,使土壤水分亏缺有关。由此可见,土壤水分状况可能是羊草光合速率决定性的影响因素,而气温和相对湿度则是次生的影响因素。

Water Use of Leymus chinensis Community

Soil moisture of Leymus chinensis (Trin.) Tzvel. community has obviously stratified phenomena: the layer (0-40 cm) in which roots are concentrically distributed is directly influenced by precipitation and evapotranspiration. It can be called interaction layer of precipitation and evapotranspiration. The layer (40-120 cm), where water-storage capacity exchange lagged exchange of the root-layer water-storage capacity and the community evapotranspiration, can be called major water-storage layer. The layer (under 120 cm) can be called water relatively stable/balanced layer. The year 1996 was a normal flow year, and soil water had a surplus of 18 mm at the end of the growing season. The year 1998 was a high flow year, because leakage took place under continuous heavy rainfall, soil water had a deficit of 15 mm at the end of the growing season. Transpiration to evapotranspiration ( T/ET) value reflected not only the luxuriance degree of the community, but also the water use regime of the environmental resources. T/ET value was low (0.5) in May 1998, reaching 0.7 in June, then decreasing to 0.6 in July, due to the impact of rainfall inclining, while August reached the maximum (0.9), and September decreased to 0.6. Water use efficiency (WUE) was mainly restricted by the growing rate of plants under sufficient water condition (1998). Its seasonal changes were coincident with the grand period of growth of the plants. When both meanings of WUE and T/ET were analyzed profoundly, the concept of evapotranspiration efficiency (ETE) which can all-side reflect utilization regime of the environmental water resources was advanced.

羊草(Leymus chinensis)草地雨天放牧与非雨天放牧的绵羊采食特征

通过受控实验,比较了雨天和非雨天放牧在采食方式、采食损失量、践踏折损率以及土壤含水量和容重的差异。得出雨天放牧条件下,羊草各种采食方式的比例降低,去顶量依旧随放牧压升高而增加,但与非雨天放牧不同的是不再占主要比例。羊草采食损失量与非雨天差异不大,对于适口性更高的植物,如芦苇和全叶马兰,雨天放牧时损失更高。绵羊在冷湿环境中活动明显减少,羊草的践踏折损率各放牧压下差异不大,但芦苇的折损率依旧表现为随放牧压增强而增加。放牧后土壤15cm的含水量都低于对照小区,表明绵羊践踏加速了土壤水分的蒸发。放牧后土壤容重与放牧前和非牧区差异显著,并且容重随放牧压增强而增加。

Research on Phenotypic Diversity of Different Populations of Leymus Chinensis in Zhalong Wetlands

[Objective] This paper aimed at revealing the rules of phenotypic variation of Leymus chinensis in Zhalong wetlands and providing the scientific and theoretical bases for devising protection strategies of Leymus chinensis populations in Zhalong National Nature Reserve.[Method] Four phenotypic traits of five Leymus chinensis populations in Zhalong Wetlands were comparison and analysis using principal component analysis method and UPGMA cluster analysis method.[Result] There were significant differences among the four phenotypic traits of five populations,the order of coefficients of variation were node number〉plant height〉leaf width〉leaf length;the order of variation degrees of the populations from large to small was KQH,MD,JZ,ZK,TTG population.Results of principal component analysis suggested that the four traits were all factors led to the phenotypic differences among the populations of Leymus chinensis.Leymus chinensis of five populations were divided into three groups by cluster analysis,MD,JZ and TTG were classified as one group,KQH and ZK population were individually classified as one group.[Conclusion] Leymus chinensis had large-scale phenotypic variations and showed strong adaptability to different habitats,which was very important for selection,breeding of fine varieties and germplasm conservation.

羊草(Leymus chinensis)叶片光合参数对干旱与复水的响应机理与模拟

利用典型草原优势植物羊草（Leymus chinensis）对不同水分胁迫与复水响应的植物光合生理生态模拟实验与野外观测资料，分析研究了羊草叶片光合参数Kcmax（Rubisco的最大羧化速率）、Jmax（最大光合电子传递速率）和TPU（磷酸丙糖利用率）对干旱与复水的响应机理。结果表明，无论是模拟实验还是野外观测均显示羊草叶片的光合参数随着土壤水分的增加呈抛物线曲线变化，但各光合参数最大值对土壤水分的响应不同。温室模拟下的羊草光合参数Vcmax，Jmax和TPU在土壤含水量分别在15．56％，15．89％和16．23％时达到最大，而野外观测羊草的光合参数Vcmax，Jmax和TPU在土壤含水量分别为16．89％，17％和16．79％时达到最大。复水后羊草植株叶片光合参数的变化取决于前期干旱的影响，土壤含水量18％～19％和15％～16％处理的羊草复水后光合参数能够恢复正常，前者甚至超过正常水平，说明适宜的水分胁迫在复水后能够提高羊草叶片的光合能力，促进光合作用；土壤含水量10％～12％和7％～9％处理下的羊草复水后光合参数则不能恢复到正常水平。土壤含水量15％～16％可能是羊草光合能力在水分胁迫后能否恢复的阈值。

温度对羊草（Leymuschinensis）生长及无性系分化的影响

根据温室内的人为控制温度试验，观测温度对羊草（Ｌｅｙｍｕｓｃｈｉｎｅｎｓｉｓ）无性系分化和生长的影响，得出如下结论；温度是影响羊草株高的最主要生态因子，适宜的高温显著促进单草的伸展；温度也是促进单草分蘖的主要因子之一，羊草的生物量积累受到温度变化极值的限制，适宜的温度范围显著促进生物量积累．羊草无性系的分化和高温的天数明显正相关，无性系对高温有较强的生态适应性，甚至在高温已经抑制羊草生物量的积累的情况下，仍然对无性系的生长和分化有一定的促进作用，这充分表明了羊草无性系对温度有较强生态适应的特点．

不同改良措施对退化羊草(Leymus chinensis)草原的影响

对1983年通过不同改良措施(播种羊草、耙地、围栏封育)处理过的退化羊草草原群落特征进行比较研究,结果表明:虽然经过23 a的恢复,土壤条件仍有差别,经过耙地处理土壤容重最小,含水量最高;三种改良措施的增产效果都很明显,播种羊草、耙地、围栏封育的群落地上生物量比围栏外分别提高了127.30%、146.64%、138.04%;播种羊草和耙地处理的根茎禾草所占比例较高,而围栏外和围栏封育处理的丛生禾草所占的比例较高;三种改良措施中,旱生植物的绝对生物量都低于围栏外;耙地处理后群落多样性最高,而围栏外均匀性指数最高。综上所述:经过耙地改良所产生的效果维持时间最长,而播种羊草和围栏封育改良的后效依然存在。

羊草(Leymus chinensis)种群无性系种群动态的初步研究

本文根据1985—1990年在天然羊草群落中对羊草种群无性系的观测与统计分析,在研究羊草种群无性系生活周期的基础上,探讨了其种群动态,建立了用转移概率矩阵表示的种群动态模型。通过用两种营养繁殖系数R_(v1)和R_(v2)模拟种群密度变化,发现用转移概率矩阵种群动态模型和现存种群营养繁殖系数R_(v2)可以预测羊草种群密度。

不同群落类型对羊草（Leymus chinensis）种群生殖分配的影响

通过对羊草种群在不同生境条件下干物质和营养元素在植株不同部位的配置研究，结果表明：羊草种群在干物质方面的配置为：根＞茎＝叶＞果实；Ｃ元素在单草植株的各个部位均匀分配，Ｎ元素的配置表现为：叶＞果＞根＝茎；Ｐ元素的配置表现为：果＞叶＞根＝茎，粗灰分表现为：根＝叶＞果＞茎．营养元素的配置在克氏针茅、大针茅、羊草三个群系类型之间，无论是什么部位都无显著差异，而这三个群系类型都与贝加尔针茅类型有显著差异，差异主要表现在茎和叶中．

退化羊草（Leymus chinensis）草原恢复演替动态的研究

对退化羊草（Ｌ．ｃｈｉｎｅｎｓｉｓ）草原围封后１１年的群落特征进行了研究分析．结果表明：退化草原在恢复过程中单位面积内植物种丰富度增加．但组成整个样地的种类成分变化不大．多样性指数中期增加后期呈现下降趋势，物种在群落中所占比例大小是造成多样性指数变化的主要因素，而与丰富度关系不大．均匀性指数在恢复过程中呈下降趋势．羊草、冰草（Ａｇｒｏｐｙｒｏｎｍｉｃｈｎｏｉ）、针茅（Ｓｔｉｐａ）在演替过程中呈持续增加趋势，相反，冷蒿（Ａｒｔｅｍｉｓｉａｆｒｉｇｉｄａ）、木地肤（Ｋｏｃｈｔｉａｐｒｏｓｔｒａｔａ）呈现下降趋势．１１年的恢复过程可划分为冷蒿＋丛生小禾草＋羊草群落，冷蒿群落向羊草群落的过渡阶段；羊草＋冰草、冷蒿＋丛生禾草群落和羊草＋冰草＋丛生禾草群落４个阶段．１１年的封育，退化群落并未恢复到羊草草原顶极群落的水平．

Effects of Various Phytohormones on Seed Germination and Seedling Growth of Leymus Chinensis

[Objective] To explore the effects of various phytohormones at different concentrations on the seed germination and seedling growth of Leymus Chinensiss （ L. chinensis）. [ Method ] The seeds of two varieties of L. chinensis were respectively treated with four kinds of phytohormone [ gibbereUin （ GA ）, 2,4-D, naphthalene acetic acid and 6-benzyl aminopurine （6-BA） ] for the observation of seed germination. The seedling growth of natural L. chinensis was observed after the seedlings were respectively treated with these phytohormones. [Result] The germination percentage of L. chinensis was promoted by the GAs and 6-BA at low concentration and inhibited by these two kinds of phytohormone at high concentration. Moreover, they promoted the seedling growth of L. chinensis, and the GA3 had better effect. However, the NAA and 2,4-D at any concentration inhibited the seed germination and seedling growth of L. chinensis. [ Conclusion] The various phytohormones have different effects on the seed germination and seedling growth of L. chinensis.

遮光和去叶处理对羊草(Leymus chinensis)无性系分株间碳物质转移的影响

羊草无性系分株间的生理整合研究，采用分别对由同一根茎相连的两颗羊草分株进行了两颗分株全部遮光、一颗分株遮光、一颗分株去叶及对照，而后分析了不同处理样品的全碳百分比含量．结果表明：在遮光干扰或去叶干扰下，都有碳物质从未被干扰的分株向被干扰的分株转移．而且，强烈的干扰会导致植株分解其结构物质，只剩纤维素骨架，从而使其全碳百分比含量增高．在遮光干扰下和去叶干扰下，碳物质转移量的百分比约分别为１．４３％和３．８８％．

氮添加对锡林郭勒灌丛草原羊草(Leymus chinensis)化学计量特征的影响

本研究以内蒙古锡林郭勒小叶锦鸡儿(Caragana microphylla)灌丛草原优势物种羊草(Leymus chinensis)为研究对象,研究氮添加对羊草碳、氮、磷元素含量及其化学计量特征的影响。结果表明氮添加对羊草茎叶N,P含量和叶片C∶N,C∶P影响显著;不同氮添加水平对灌丛下和灌丛间羊草C,N,P含量及其化学计量特征的影响存在分异;随氮添加的增加,灌丛间羊草茎叶C∶N和叶片C∶P呈降低趋势,灌丛下羊草茎叶化学计量特征变化不显著;灌丛下羊草茎叶C,N,P含量及其化学计量特征的变异系数均低于灌丛间羊草;氮添加显著影响灌丛间羊草茎叶N含量,C∶N和C∶P,但是,氮添加对灌丛下羊草茎叶化学计量特征影响不显著。小叶锦鸡儿灌丛化过程可能会削弱氮添加对草本植物叶片C,N,P含量及化学计量特征的影响,本研究结果为草原生态系统管理提供了新的视角和重要的理论依据。

羊草(Leymus chinensis(Trin)Kitag.)的小孢子发生和雄配子体形成

本文研究了羊草小孢子发育和雄配子体形成,主要结论如下:(1)小孢子母细胞减数分裂过程中的胞质分裂为连续型。四分孢子为平面型,单核小孢子第一次有丝分裂形成生殖细胞和营养细胞,它们之间有明显的细胞壁,对PAS染色和苯胺兰染色诱导荧光均呈负反应,成熟花粉粒为三细胞,细胞内贮藏丰富淀粉粒,(2)药璧发育为单子叶型,绒毡层细胞属分泌型,母细胞减数分裂时绒毡层细胞具一或二核,在单核小孢子早期,绒毡层细胞有向花药腔肥大增生和绒毡层细胞互相融合形成变形绒毡层的现象。