土壤干旱胁迫对不同种群羊草光合及叶绿素荧光的影响

采用室外盆栽干旱胁迫试验方法,对干旱条件下3个不同种群羊草净光合速率、叶绿素荧光参数、生物量及其分配格局进行了研究。结果表明,不同种群羊草对照和轻度胁迫条件下的净光合速率差异不显著,重度胁迫下嘎松山种群羊草光合速率显著大于另外2个种群。不同干旱胁迫处理间、不同种群羊草的F0差异不显著。3个种群羊草叶片的最大荧光(F m)、可变荧光(F v)、原初光能转换效率(F v/F m)、PSⅡ潜在活性(F m/F0)和Tm值随干旱胁迫加剧呈下降趋势,但各种群下降的幅度不同。各种群羊草的生长对轻度干旱胁迫不敏感,重度胁迫下羊草生物量均呈下降趋势,但不同种群变化存在差异。重度胁迫下,羊草样地种群生物量显著低于对照和轻度胁迫,而达里湖种群和嘎松山种群在与对照、轻度胁迫差异不显著。随胁迫强度加大,达里湖种群和嘎松山种群地下部分投入比例增加,羊草样地种群在重度胁迫下地下生物量却显著减少。生物量与PSⅡ光化学效率(F v/F m)呈显著正相关,与初始荧光F0呈显著负相关;净光合速率与F v、F m、F v/F m、F m/F0之间呈显著或极显著正相关,与F0呈显著负相关。

Effects of Soil Drought Stress on Photosynthesis and Chlorophyll Fluorescence for Different Leymus chinensis Populations

Soil drought stress effects were studied on three Leymus chinensis populations from different geographic locations (Dali lake, Leymus chinensis plot, Gasong Mountain) of the Inner Mongolian Plateau. Seedlings were maintained under three treatments:one well-watered condition (Control, keeping the soil at field capacity) and two different water deficit conditions (T1, mild stress; T2, severe stress). Net photosynthesis rate, chlorophyll fluorescence parameters,dry matter accumulation and allocation were measured during the onset of stress. There was no significant difference in net photosynthesis rate among the populations under CK and T1, but the net photosynthesis rate of Gasong Mountain population was higher than those of the others under sever stress. No significant differences in F0 among the populations and the treatments were observed. With stress intensification,Fm,Fv,Fv/Fm,Fm/F0 and Tm of leaf in the three populations decreased with varied degrees. No significant population differences in dry matter accumulation were detected under control (CK) and mild stress (T1).In severe stress (T2), biomass of Leymus chinensis plot plants decreased significantly compared with CK and T1, while there were no significant differences among the treatments in the other two populations. Root/shoot ratio increased with increased stress levels and stress duration in Dali Lake and Gasong mountain populations, but below-ground biomass decreased in Leymus chinensis plot population under severe stress