紫花苜蓿和沙打旺幼苗的生物量分配、叶片气体交换和水分关系对土壤干旱的响应——西北农林科技大学2010.pdf

PHOTOSYNTHETICA 48 (4): 481-487, 2010 Biomass partition, leaf gas exchange and water relations of alfalfa and milkvetch seedlings in response to soil drying B.-C. XU*,**,+, X.-P. DENG*,**, S.-Q. ZHANG*,**, and L. SHAN*,** State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A F University, * Yangling, Shaanxi 712100, P.R. China Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, ** Shaanxi 712100, P.R. China Abstract This study compared physiological and growth responses to water stress of two legume species during the seedling stage. Potted alfalfa (Medicago sativa L. cv. Algonquin) and milkvetch (Astragalus adsurgens Pall. cv. Pengyang early- maturing vetch) seedlings were grown under well-watered [soil water content (SWC) maintained at 14.92% daily] or water-stressed conditions (drying) for 15 days. Net photosynthetic rate (PN), transpiration rate (E) and stomatal conductance (g ) of both species decreased parabolically. When SWC decreased to 7.2% and 10.3%, g values for alfalfa s s and milkvetch were significantly different from those of the respective well-watered plants (p 0.05). When SWC decreased to 6.6% for alfalfa and 6.8% for milkvetch, leaf water potentials (ψL) were significantly different from those of the well-watered plants (p 0.05). Thus the difference between the SWC thresholds for a nonhydraulic root signal (nHRS) and a hydraulic root signal (