Effects Of Pruning On Photosynthesis And Leaf Anatomical Structure Of Chimonanthus Praecox

This study is exploring the effect of pruning on growth,photosynthesis and leaf anatomical structure of Chimonanthus praecox,and to analysis the relationship between the change of leaf anatomical structure and photosynthesis of Chimonanthus praecox.In this study,Chimonanthus praecox is six years old,and pruning in April 2014 and April 2015.Removed the redundant branches from the base of plants,and removed the apical dominance of saving branches.Pruned the excessive growth of shoots,and pruned crowded or damaged shoots of canopy.Cuting back the perennial branches of canopy to improving the ventilation and transmittance conditions.The second pruning 50-60 days later,measured the diurnal variation of photosynthetic parameters by Li-6400.Two months later,researched the stoma stamp by nail polish.Four months later,researched the section of Chimonanthus praecox leaf with paraffin section method and growth indicators,and measured the leaf anatomical structure parameters and stomata parameters by Olympus stereoscopic microscope.The study is providing theoretical basis for the cultivation and management of Chimonanthus praecox,and providing production guidance for the garden planting of Chimonanthus praecox.Statistics and analysis of all data,the results show as the following:(1)After pruning,the average of diurnal variation of net photosynthetic rate,stomata conductance and transpiration rate of Chimonanthus praecox were significantly increased(P<0.05).And the average of diurnal variation of apparent mesophyll conductance was dramatically increased(P<0.01),and the intercellular CO2 concentrations was significantly decreased(P<0.05),no significantly changed in water use efficiency,the stoma limited value and the vapor pressure deficit.At the same time,the variation trend of the net photosynthetic rate,stomata conductance,transpiration rate,intercellular CO2 concentrations,stoma limited value,water use efficiency and vapor pressure deficit of Chimonanthus praecox have not significantly changed.However,the variation trend of apparent mesophyll conductance have changed dramatically(P<0.01),which was from a single-peak trend to a double-peak trend.(2)After pruning,the chlorophyll a and chlorophyll content of Chimonanthus praecox leaf were significantly increased(P<0.05),and the chlorophyll a/b and leaf mass area ratio were dramatically increased(P<0.01).The increment of leaf length,plant height and crown diameter of the pruning group were dramatically superior to the CK(P<0.01).And the increment of leaves area and leaf width of the pruning group were dramatically lower than the CK(P<0.01).(3)After pruning,the stoma width of Chimonanthus praecox leaf was dramatically increased(P<0.01),and the stoma length,width of stomtal aperture,and stomatal density were significantly increased(P<0.05).The leaf thickness and palisade tissue of Chimonanthus praecox were significantly increased(P<0.05),and the thickness rate of palisade and sponge tissue was dramatically increased(P<0.01),no significantly changed in the sponge tissue thickness,the epidermal thickness and vein protuberant degree.(4)The chlorophyll a/b was significantly positively correlated(r=0.679)with net photosynthetic rate,dramatically positively correlated(r=0.836)with stomata conductance,and dramatically negatively correlated(r=-0.890)with the intercellular CO2 concentrations.The stoma length was dramatically positively correlated(r=0.873)with net photosynthetic rate,and significantly positively correlated(r=0.712)with stomata conductance.The stoma width was dramatically positively correlated with net photosynthetic rate(r=0.904)and stomata conductance(r=0.830).The width of stomtal aperture was significantly positively correlated with net photosynthetic rate(r=0.725)and stomata conductance(r=0.746).The palisade tissue was significantly positively correlated(r=0.668)with net photosynthetic rate,and significantly negatively correlated(r=-0.729)with the intercellular CO2 concentrations.The thickness rate of palisade and sponge tissue was dramatically positively correlated(r=0.861)with chlorophyll a/b,and significantly positively correlated(r=0.657)with the net photosynthetic rate,and dramatically negatively correlated(r=-0.831)with the intercellular CO2 concentrations.(5)In conclusion,after pruning,the chlorophyll content and specific leaf weight of Chimonanthus praecox were significantly increased,and the leaf morphological characteristics and anatomical structure characteristics were changed significantly.And the photosynthetic rate and efficiency were significantly increased,which were beneficial to the growth of Chimonanthus praecox.