Abstract:Diurnal changes in leaf azimuth angle,lamina angle,midrib angle under two natural regimes and chloroplast movements when subjected to different light pretreatments were investigated for several hybrid poplar clones.Changes in leaf orientation in a clear day were stronger than that in a cloudy day especially for triploid clones,suggesting these clones were sensitive to light.From 9:00 to 11:00 in the clear day,the triploid clones ZH6 and B346 evaded strong light by changing in azimuth angle.Around midday hou...