【作者】 杨季云；

【导师】 周道玮；

【作者基本信息】 东北师范大学 ， 生态学， 2011， 博士

【摘要】 花苜蓿是一种非常优良的多年生豆科牧草,在我国畜牧业发展中占有重要地位。它是苜蓿属中唯一可以适应干旱环境、极低降雨量的石质化环境和寒冷冬季的物种,并且比紫花苜蓿具有更加优越的抗寒性和营养利用效率,是公认的适合在寒冷地域种植的极佳豆科牧草。即便如此,国内外对花苜蓿的研究仍然较少,并且缺乏系统性,花苜蓿的生长过程、种子发育和收获、根系特征以及盐碱胁迫下逆境生理生态学研究都寥寥无几。花苜蓿生态幅较广,包含许多适应于各自原始生境的生态型,对花苜蓿生态型分异的研究对选育和杂交育种都具有重大意义。本论文通过对两种生态型花苜蓿形态分异、不同密度条件下的生长发育、种子最佳收获时期的研究,得出:1)林下和草甸两种生态型花苜蓿叶片、荚果和种子具有显著的形态分异,并且这种分异不随生长环境的变化而发生变化,具有适应性特征,是局域适应的结果;2)种植密度对花苜蓿株高、主茎直径、叶片数、分枝数和各器官生物量的影响在不同生活史阶段具有差异。在生长季初期,出苗后30天,种植密度对各密度下的花苜蓿生长无显著影响;在生长季末期,种植密度对两种生态型花苜蓿的株高、主茎直径、叶片数、分枝数和各器官生物量都具有显著影响,株高、主茎直径、叶片数、分枝数和单株总生物量都随密度增大而减少;3)种植密度与林下花苜蓿的主茎直径、叶片数、叶生物量和单株总生物量显著相关,与草甸花苜蓿的叶片数和叶生物量显著相关,两种生态型花苜蓿的单株总生物量都与株高、主茎直径、叶片数、分枝数和各器官生物量显著相关。林下和草甸两种生态型花苜蓿的最适种植密度都是278株/m²,可获得最大干草产量分别为2916.7 kg/hm²和2794.5 kg/hm²,最大繁殖生物量分别为333.33 kg/hm²和622.23 kg/hm²;4)由于花苜蓿开花不齐、荚果成熟期不一致的原因,不同收获时期的花苜蓿种子具有不同的产量和质量,种子的最佳收获时期就是在获得较高种子产量的同时,种子质量也较高的时期。草甸花苜蓿的种子最佳收获期是在初花期后57⁶0天,种子产量可达92.67⁹9.00 kg/hm²;林下花苜蓿的种子最佳收获期是在初花期后51⁶0天,产量可达93.33¹16 kg/hm²;5)林下花苜蓿具有叶片数多,分枝数多,单株生物量较大;花期较短、结荚相对集中、果序数量多,种子千粒重大、发芽百分数高、种子产量高、根系发育能力强等优点,是花苜蓿选育和杂交等工作的优良材料,具有潜在的发展前景。通过对三份花苜蓿材料根系特征的研究发现:不同花苜蓿材料的根系主根长、侧根发生位置和主根生物量差异极显著;林下花苜蓿具有比直立型和草甸花苜蓿更强的根系发育能力,表现为主根入土更深、侧根数更多、根系生物量更大。花苜蓿根系的垂直分布格局是主根直径、主根生物量和侧根生物量随土层深度增大而减小,主根生物量主要分布在根颈下0¹0cm主根段,侧根生物量主要分布在根颈下0²0cm主根段。主根直径、根颈直径和根颈入土深度适合用来作为花苜蓿材料的选育指标。通过对林下花苜蓿种子发育过程及与硬实形成关系的研究发现:随发育天数的增加,林下花苜蓿种子含水量、电导率逐渐减低;鲜重、发芽百分数、千粒重先升高后降低;干重、硬实率逐渐升高。种子种皮的栅栏细胞和种脐的两层栅栏细胞均不透水是导致林下花苜蓿种子硬实的原因之一。通过对花苜蓿在混合盐碱胁迫条件下生长、光合、无机离子和有机溶质积累的研究,我们发现:1)混合盐碱胁迫中,盐度（盐浓度）、碱度（pH）和二者交互作用都显著影响花苜蓿幼苗的地上部分含水量、相对生长速率、根系活力和存活率。花苜蓿地上部分和根系的相对生长速率、地上部分的含水量都随盐度和碱度的增加而降低。幼苗的根系活力被低碱度和盐度的联合作用促进而有所升高,在高碱度和盐度处理下,幼苗的根系活力随盐度增加而逐渐降低。碱度对幼苗存活率的影响大于盐度;2)混合盐碱胁迫处理下,盐度（盐浓度）和碱度（pH）显著影响花苜蓿幼苗的叶绿素a、叶绿素b和类胡萝卜素含量,这些色素的含量都随着盐度和碱度的增加而表现出降低的趋势。盐度、碱度及其交互作用都显著影响花苜蓿幼苗叶片的光合速率、气孔导度和胞间CO₂浓度。光合速率、气孔导度和胞间CO₂浓度都随盐浓度和pH值增加而降低;3)花苜蓿地上部分和根系对混合盐碱胁迫的生理响应不同。草酸积累在花苜蓿对混合盐碱胁迫的响应中具有重要作用。在花苜蓿地上部分,盐度和缓冲能力更能体现混合盐碱胁迫的作用;在花苜蓿根系中,pH和缓冲能力更能体现混合盐碱胁迫的作用。更多还原

【Abstract】 Medicago ruthenica （Linn.） Trautv.is one of the most important and outstanding perennial forage legume in the world, and it plays an important role on livestock husbandry in China. It is a unique species of Medicago adapted to dry, stony locations with extremely low snowfall and very cold winters. It has more superior cold-tolerance and nutrition utilization efficiency than Alfalfa （Medicago sativa L.）, and was considered to be the most optimal forage legume cultivated in cold region. Nevertheless, the research on M. ruthenica is still less and lack systematicness, especially on the growing, development and harvest of seed, characteristics of root system, physioecological responses under salt-alkaline stress. M. rithenica distributes widely and contains many ecotypes which adapted to each original habitat, research on the ecotypic differentiation is of great significance for crossbreeding and hybridization.The results of morphological differentiation of two ecotypes, growing development under different density, seed optimal harvest time research indicated （1） The morphological differentiations of leaves, pods and seed in two ecotypes of M. ruthenica were evident. The differentias were adaptive, did not change with the environment alteration, results of local adaptation.（2） The effects of planting diversity on height, stem diameter, number of leaves, number of branches and biomass of every organ were diverse in different stage of M. ruthenica life history. On the beginning period of M. ruthenica growing season, 30 days after emergence, the effects of planting density on growth under all density treatments were unremarkable. In the final stage of growing season, planting density showed significantly effets on height, stem diameter, number of leaves, number of branches and biomass of every organ in both ecotypes of M. ruthenica. Height, stem diameter, number of leaves, number of branches and biomass of individual plant decreased with density increasing. （3） Planting density showed significant correlativity with stem diamter, number of leaves, leaves biomass and individual plant biomass in Woodland M. ruthenica; also showed significant correlativity with number of leaves and leaves biomass in Meadow M. ruthenica. Individual plant biomass markablely correlated with height, tem diameter, number of leaves, number of branches and biomass of every organ in both ecotypes. The optimal planting density for two ecotypes was 278 plants/m²,maximal hay yield for woodland and meadow M. ruthenica respectively were 2916.7 kg/hm² and 2794.5 kg/hm², maximal reproductive biomass were 333.33 kg/hm² and 622.23 kg/hm².（4） Seed of M. ruthenica which harvested on different period had diverse yield and quality due to irregular blossomming and pod maturation. The optimal harvest time was the period that can gain higher yield and higher quality of seeds. The optimal harvest time for meadow M. ruthenica was 57⁶0 days after initial anthesis, with seeds yield was 92.67⁹9.00 kg/hm²; for woodland M. ruthenica was 51⁶0 days after initial anthesis, with seeds yield was 93.33¹16.00 kg/hm². （5） The merits of woodland M. ruthenica such as more leaves, more branches, more individual plant biomass, shorter blooming period, fructification more synchronous, more infructescence, bigger thousand seeds weight, higher germination percentage, more seed yield and better root development ability were basis for breeding and hybridization work. It is a eminent material and had potential developmental prospect.Differences of taproot length, lateral root position and taproot biomass between three M. ruthenica were remarkable. Woodland M. ruthenica had better root development ability than Zhili and meadow, showed longer taproot, more lateral root and bigger root biomass. Vertical distribution pwttern of M. ruthenica root system was taproot diameter, biomass od taproot and lateral root decreased with soil depth increasing; taproot biomass mainly distributed in 0¹0cm section under root crown, lateral biomass mainly distributed in 0²0cm section under root crown. Taproot diameter, diameter and depth of root crown were acceptable indexes for breeding excellent M. ruthenica.The results of seed development and its relationship with hardseedness indicated that with the increasing of development days, water content and electrical conductivity of woodland M. ruthenica seeds decreased; fresh weight, germination percentage and thousand seeds weight raised at first reduced finally; dry weight and hard seed percentage rised gradually. The impermeability of palisade cells in spermoderm and seed hilum was one of the reason for seed hardness in woodland M. ruthenica.According to the physioecological responses of M. rithenica to mixed salt-alkaline stresses, we found that: （1） Salinity（concentration）, alkalinity（pH） and their interaction significantly influenced water content, relative growth rate, root activity and survival rate of M. ruthenica under mixed salt-alkali stresses. RGR and water content of shoots decreased with the increasing of salinity and alkalinity. Root activity was promoted by the combine of low salinity and low alkalinity, but decreased with salinity increasing under high alkalinity and salinity stresses. The influence of alkalinity on survival rate was bigger than salinity. （2） Salinity（concentration） and alkalinity（pH） significantly influenced the content of chloropyll a ,b and carotenoid in M. ruthenica under mixed salt-alkali stresses. The contents were all lower with salinity and alkalinity raising. Salinity（concentration）, alkalinity（pH） and their interaction significantly influenced photosynthetic rate, stomatal conductance and intercellular CO₂ concentration of M. ruthenica leaves. The photosynthesis indexes reduced with salt concentration and pH increasing.（3） Physioloucal responses of shoots and roots to mixed salt-alkali stresses in M. ruthenica were different. Oxalate accumulation showed very important effect on responses to mixed salt-alkali stresses in M. ruthenica. Salinity and buffer capacity reflected the mixed salt-alkali stresses better in shoots of M. ruthenica, but in roots, pH and buffer capacity reflected the mixed salt-alkali stresses better.更多还原