NaCl胁迫下3种榆树幼苗光合作用特性的研究

Research on photosynthetic characteristics of three elm species seedling under salt stress

以岩榆、南方岩榆和白榆的1a生盆栽苗为研究对象,测定其在不同浓度NaCl胁迫下的光合作用指标,结果表明:(1)NaCl胁迫初、中期,随着浓度的增大和胁迫时间的延长,各种幼苗的净光合速率(Pn)、气孔导度(Cond)、胞间CO2浓度(Ci)和蒸腾速率(Tr)均呈不同幅度的下降趋势,以白榆降幅最大,南方岩榆次之,岩榆最小。叶面水气压亏缺(Vpdl)均有增加趋势,但增幅不明显。(2)NaCl胁迫后期,随盐分浓度的增加和时间的延长,净光合速率、气孔导度和蒸腾速率呈逐渐降低的的趋势,且降幅明显高于初期和中期。(3)3种榆树幼苗净光合速率的下降在NaCl胁迫初和中期是气孔限制的结果,后期为非气孔限制和气孔限制共同作用的结果。(4)不同的NaCl浓度与净光合速率、气孔导度、胞间CO2浓度和蒸腾速率呈负相关,与叶面水气压亏缺呈正相关。不同时期岩榆叶面水气压亏缺与NaCl浓度均呈显著或极显著的相关性,白榆和南方岩榆在初中期与NaCl浓度的相关程度达到显著或极显著的水平,但后期相关性不显著。

Taking one-year seedlings of three elm species potted as studied subjects ,we respectively determined its photosynthesis under salt stress in order to disclose the effect of salt stress on its photosynthesis parameters and lay theroretic foundation for introduction and cultivation of Ulmus thomasii and U. Crassifolia. The results showed that （1）with increase of NaCl concentration and time at prometaphase stage its net production rate （Pn）, stomatal conductance （Cond）, carbon dioxide between cells （Ci） and transpiration rate （Tr） all presented a decreasing trend, the decreasing amplitude of U. pumila was the biggest, that of U. thomasii the smallest among three elm species. meanwhile its vapor pressure devoid of leaves （Vpdl） presented a rising trend, but its decreasing amplitude was not obvious; （2）with increase of NaCl concentration and time, Pn, Ci and Tr came to display a decreasing trend, and its decreasing amplitudes were higher than those of prometaphase stage ; （3） at prometaphase stage the decreasing Pn was caused by stomatal inhibition, but latterly it resulted from both non-stomatal inhibition and stomatal inhibition together; （4）there were a negtive correlations between Pn, Ci, Tr, cond, and different NaCl concentrations, but positive correlations between Vpdl and different NaCl concentrations. During different sahstress periods there were significant correlations between U. thomasii Vpdl and different NaCl concentrations. For U. crassifolia and U. pumila there was a significant correlation at prometaphase stage, but not notable in the later stage.