土壤水分胁迫对紫花苜蓿光合特性及其生物量的影响

通过大田试验对不同水分胁迫下紫花苜蓿的光合特性及产量进行研究，结果表明: ① 土壤水分胁迫对紫花苜蓿光响应参数影响显著，随着水分胁迫的加剧，最大净光合速率、表观量子效率、光饱和点逐渐降低，暗呼吸速率、光补偿点逐渐升高，从而直接影响紫花苜蓿光合作用对弱光的吸收和转化效率。② 随着水分胁迫的加剧紫花苜蓿叶片的和蒸腾速率呈显著的下降趋势，气孔导度呈先下降后上升的趋势，表明轻度水分胁迫下气孔因素是下降的主要因素，中度和重度水分胁迫下非气孔因素是净光合速率降低的主要因素。③适度水分胁迫可提高紫花苜蓿叶片的水分利用效率。④ 轻度水分胁迫与充分灌溉干草产量之间无显著差异，表明轻度水分胁迫能达到高产节水的目的。

A field experiment was conducted to investigate the photosynthetic characteristics and yield of alfalfa under different water stresses. The results show that:
① Soil water stress exerts a significant effect on the light response parameters of alfalfa. As water stress intensifies, the maximum net photosynthetic rate, apparent quantum yield, and light saturation point gradually decrease, while the dark respiration rate and light compensation point gradually increase, which directly affects the absorption and conversion efficiency of alfalfa photosynthesis to low-intensity light.
② As water stress intensifies, the transpiration rate of alfalfa leaves shows a significant downward trend, while the stomatal conductance first decreases and then increases. This indicates that stomatal factors are the main cause of the decline under mild water stress, whereas non-stomatal factors are the primary contributors to the reduction in net photosynthetic rate under moderate and severe water stress.
③ Moderate water stress can improve the water use efficiency of alfalfa leaves.
④ There is no significant difference in hay yield between mild water stress and full irrigation conditions, indicating that mild water stress can achieve the goals of high yield and water conservation.