低水平叶-气水气压差条件下气孔导度对其小尺度变化的响应

有关气孔对叶-气水气压差的变化响应的相关研究已进行多年并积累了大量的资料,但主要集中在较高水平VPD条件下气孔对较大尺度变化的稳态响应等方面.本试验以棉花(Gossypiumhirsutum L.)和玉米(Zea mays L.)为研究对象,在较低水平VPD条件下研究了气孔对较小尺度VPD变化的连续反应.研究表明,VPD增加时,气孔导度迅速上升而形成一个"峰",然后下降达到稳定状态,此时,gs与VPD变化之前不同,大小因植物种不同而不同;VPD减小时,gs快速下降而形成一个"谷",然后上升达到稳定状态,此时,gs也与VPD变化之前不同.分析认为:即使在较低VPD水平,VPD变化尺度较小,气孔也能敏感地作出反应;整个气孔响应过程可能包括一个瞬时变化以及随后的渐变过程.

Stomatal conductance in response to the smaller changes in leaf-air vapour pressure deficit

Stomatal response to leaf-air vapour pressure deficit(VPD) has been studied over the years mainly on steady-state responses with larger VPD changes at higher VPD levels. In this study, stomatal responses to smaller VPD changes were investigated at lower VPD levels. Stomatal conductance(gs) was measured within 30 min after VPD change with leaves of cotton(Gossypium hirsutum L.) and maize(Zea mays L.). When VPD was increased, gs instantaneously increased as an overshooting "peak", and then decreased to the steady status that may be greater or less than the initial value measured before VPD increase due to different species. When VPD was reduced, gs instantaneously decreased to an overshooting "valley", and then increased to the steady status which would be less or bigger than the initial values.The results showed that stomata can respond sensitively to smaller VPD changes at lower VPD levels and the whole responding process contains an overshooting phase and a gradual changing phase.