Light induces leaf orientation and chloroplast movements of hybrid poplar clones
光诱导下杂种杨无性系叶角和叶绿体的运动

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 hours light evasion movements could be achieved by changing midrib angle,declining leaf tilt downwards for triploid clones ZH6 and B346 and maintaining leaf blade erected for diploid clone B11.In other daytime all clones optimize in interception of solar irradiance by changing both of midrib angle and lamina angle.In both clear and cloudy days,rhythmical movement involved in change of lamina angle.The chloroplasts in the palisade cell moved and lined along the radial wall of cell when subjected to strong irradiance,which made the chloroplasts have less areas to expose direct light.Whereas the chloroplasts in the palisade cell distributed all over the cell when receiving darkpretreatment,which made the chloroplasts have much more areas to receive direct light.The triploid clones were more sensitive to light induction than that of diploid clones in the movements of leaf and chloroplast.