干旱区生态环境知识资源中心

Net photosynthesis (P(N)), transpiration (E) and water use efficiency (WUE) responses to prolonged drought and subsequent recovery after rewatering were investigated in sun and shade leaves of two maize (Zea mays L. cv. Pioneer 3839 SC) stands with different plant density (6.2 and 10.8 plants per m2). Drought stress was induced by the very small amount of precipitation (60 mm) during the 57 d of the study period. P(N) was higher in both sun and shade leaves in the low density stand through the study period, presumably owing to higher degree of intraspecific competition in the denser stand. P(N) did not decrease under severe drought stress in the sun leaves of the two stands. WUE decreased in sun leaves in both stands. P(N) decreased most in the shade leaves of the high density stand, due to less available radiation in this stand. The higher degree of intraspecific competition might also contribute to this. The short- and long-term responses by the stands to irrigation differed greatly, as WUE decreased in the high density stand and increased in the low density stand. Thus P(N) was more strongly affected in the high density stand because of the higher degree of interactive drought stress and intraspecific competition concurrently with considerable loss of stomatal control of E.