遮阴对米槁幼苗光合生理指标的影响

Effects of shading on photosynthetic physiological responses of the medicinal plant Cinnamomum migao

米槁是我国少数民族特色药用植物之一,为了探索其对光的需求及其生理适应性,解决其产量下降的问题,笔者以1年生米槁幼苗为试验对象,通过Li-6400测定在不同尼龙网遮阴环境下(透光率分别为100%,75%±5%,40%±5%)米槁幼苗培养120d的光合生理特性,了解其变化规律.结果表明:随着遮阴加剧,米槁幼苗叶片Chla(叶绿素a)、Chlb(叶绿素b)、Chl(总叶绿素)、Car(类胡萝卜素)含量上升,Chla/b含量的比值下降.遮阴加剧使米槁光饱和点有所增加,且净光合速率(P_n)、气孔导度(G_s)皆先增大后快速减小.胞间CO_2浓度(C_i)恰好相反,其随遮阴的加剧先降后升,蒸腾速率(T_r)则持续下降,而水分利用率WUE不断升高.透光率为75%±5%时米槁P_n、G_s最大,C_i最小,为米槁生长的最适透光率.

Cinnamomum migao is one of the special medicinal plants of ethnic minorities in China. In order to explore its photosynthetic requirement and physiological adaptability, and to solve the problem of yield decline, the photosynthetic physiological characteristics of one-year-old seedlings of C . migao were measured by Li-6400 under different nylon net shading conditions for 120 days (transmittance was 100%, 75%±5%, 40%±5%) in the experiment to understand its laws of change. The results showed that the contents of Chla (chlorophyll a), Chlb (chlorophyll b), Chl (total chlorophyll) and Car (carotenoid) increased and the ratio of Chl a/b decreased with shading increasing. At the same time, the net photosynthetic rate ( P n ) and stomatal conductance ( G s ) of the C . migao leaves increased first and then decreased rapidly with the increase of shading. Intercellular CO 2 concentration ( C i ), on the contrary, decreased first and then increased, transpiration rate ( T r ) continued to decline , and WUE increased with shading. When the light transmittance was 75%± 5%, the P n and G s values were the largest and the C i values were the smallest. Therefore, it was the optimum light transmittance for the growth of the tree.