遮阴对3种珍贵乡土阔叶树种幼苗生长及光合作用的影响

Influence of Shading on the Seedling Growth of Three Precious Native Tree Species and Photosynthesis

探讨3种珍贵乡土阔叶树种幼苗在遮荫条件下的生长及光合作用,为城市绿化乔木树种的引种选择提供理论依据,分别在遮阴处理(50%和80%的遮阴率)与无遮阴(CK)对照条件下,探究桢楠(Phoebe zhennan)、红椿(Toona ciliata)、香樟(Cinnamomum camphora)3个珍贵乡土树种在不同光照条件下形态和生理的响应情况。结果表明,遮荫处理下的地径和苗高大部分均小于对照组,其中香樟最为显著。在各处理间,3种乡土树种的平均叶面积均差异显著(P <0.05),含水率差异均不显著(P>0.05),红椿比叶面积的变化较大,而香樟和桢楠没有明显的变化。香樟幼苗的叶绿素a、叶绿素b及总叶绿素随着光照强度的降低,其含量都增加;桢楠的叶绿素a、总叶绿素含量和红椿的叶绿素b随着遮荫强度的增加而降低,桢楠的叶绿素b含量增加,而红椿的叶绿素a及总叶绿素含量先降低后升高。香樟净光合速率和蒸腾速率均呈现不同程度的升高,气孔导度和胞间CO 2浓度均降低,气孔导度在不同遮阴处理下差异均显著(P <0.05);红椿净光合速率、气孔导度和蒸腾速率呈现不同程度降低,胞间CO 2浓度升高;桢楠净光合速率、气孔导度和胞间CO 2浓度呈现不同程度降低,蒸腾速率升高。香樟和桢楠对遮阴的适应性较强,而红椿则适宜在强光照条件下栽植,这为城市园林绿化乔木树种的选择提供了理论依据。

The purpose of this study was to investigate the growth and photosynthesis of three precious native broad-leaved tree species under shading conditions,and to provide a theoretical basis for their introduction to the selection of urban greening arbor species.Through different shading treatments (50% and 80% shading rates) and without shading (control),three species of Phoebe zhennan,Toona ciliata ,and Cinnamomum camphora were studied.Morphological and physiological responses of precious native tree species under different light conditions were observed.Most of the ground diameter and seedling height under shading were smaller than the control,especially for C.camphora .Among the shading treatments,the average leaf area of the three native tree species was significantly different (P < 0.05),the water content difference was not significant (P >0.05),and the specific leaf area of the T.ciliata varied greatly,while C.camphora and P.zhennan had no obvious change.The contents of chlorophyll a,b and total chlorophyll of C.camphora seedlings increased with the decrease of light intensity.The contents of chlorophyll a,total chlorophyll of P.zhennan ,the content of chlorophyll b of T.ciliata decreased with the increase of shading intensity.With the increase of shading intensity,the content of chlorophyll b of P.zhennan increased,while the content of chlorophyll a and total chlorophyll of T.ciliata decreased first and then increased.With the increase of shading intensity,the photosynthetic rate and transpiration rate of C.camphora increased to different degrees,stomatal conductance and intercellular CO 2 concentration decreased,stomatal conductance was significantly different under different shading strengths (P < 0.05);net photosynthetic rate and stomata of T.ciliata ,conductance and transpiration rate decreased to different degrees,and the intercellular CO 2 concentration increased.The net photosynthetic rate,stomatal conductance and intercellular CO 2 concentration of P.zhennan decreased to different degrees,and the transpiration rate increased.The adaptability of C.camphora and P.zhennan to shading is strong,while T.ciliata is suitable for planting under strong light conditions,which provides a theoretical basis for the selection of urban landscaping arbor species.