麦田冠层气孔导度的分层研究

THE STUDY OF CANOPY STOMATAL CONDUCTANCE WITH DIVIDING LAYER METHOD IN THE WINTER WHEAT FIELD

小麦灌浆期和乳熟期冠层各层叶片上、下表面的气孔导度之间呈正相关关系;冠层不同层的叶片气孔导度从早到傍晚有平行变化的趋势,数值上存在较大的差异,一般从冠层上到下递减。经分析,这主要与冠层叶片接受的光强自上而下递减有关,且这时所对应的叶片水势自冠层上到下递增的幅度大。测算结果表明,冠层气孔导度白天亦呈明显的日变化,灌浆期的值大于乳熟期的值。

With the measurements of leaf stomatal conductances (g_(si),i=1,2,3,or 4) in different la- yers of the winter wheat canopy and the other related variables,the diurnal changes of different layer leaf stomatal conductance and canopy stonatal conductance (g_c) have been analysed in grain filling and milk stages in several aspects:There are most positive correlations between the adaxial and abaxial stomatal conductances of all different layers in both of the two grow- ing stages;During the day,in addition to its parallel changes of all layers with time,g_(si) shows the tendency of decrease from the top to the bottom of the canopy.This is mainly because the light intensity exposing to leaves should decrease in the same direction.But in some cases this change tendency disappears or reverses when the extent to which the leaf water potential in- crease from the upper layer to the lower one of canopy becomes greater.This may show the effect that leaf water potential is favorable to the open of stomata.The gc also shows the evident change in the day and the value of it in grain filling stage is larger than that of milk stage.