Photosynthetic characteristics and chlorophyll fluorescence in leaves of catharanthus roseus grown under different light intensities

Chinese. 【目的】探讨不同光强下长春花的光合生理特性,为长春花的种植提供理论指导。【方法】采用遮荫处理模拟不同的生境光强（100%、42.5%和12.5%自然光）,测定不同光强条件下生长的长春花叶片的比叶重（LMA）、光合色素含量、最大净光合速率（Pmax）、叶绿素荧光参数等光合生理指标,并对叶绿体的超微结构进行观察。【结果】随生境光强的减弱,最大净光合速率Pmax下降,12.5%光强下的Pmax是全光强下的71.4%。其它光合指标也发生适应性调整,相对正常光照,弱光下叶绿素含量上升,LMA、Chla/Chlb、Car/Chl、光饱和点（LSP）、光补偿点（LCP）下降。自然光照条件下叶绿体中的类囊体片层结构垛叠紧密,数量较多,随光强减弱,叶绿体基粒逐渐变大,基粒片层发育较差、并且数量逐渐减少。Fv/Fm,qP、NPQ及实际光量子效率ΦPSⅡ等随光强下降也都呈下降趋势。【结论】不同光强下生长的长春花叶片的光合作用和叶绿素荧光动力学特征存在很大差异。弱光条件下,尤其是12.5%光强重度弱光胁迫下,长春花叶片的光合作用受到严重影响,主要表现在ΦPSⅡ、qP和NPQ的下降,从而导致光合机构发育不良和光合能力的下降,影响其正常生长。

English. [Objective] The purpose of this experiment was to study the effects of different light intensities on the photosynthetic and physiological characteristics of Catharanthus roseus, which offered a theoretical basis for its planting. [ Method ] Different light environments （100%, 42.5% and 12.5% daylight） were simulated with shading treatments. The maximum net photosynthetic rate （Pmax）, chlorophyll fluorescence parameters, chloroplast pigments content and lamina mass per unit area （LMA） were measured and the ultrastmctural changes of chloroplasts were observed. [Result] The maximum net photosynthetic rate （Pmax） decreased when the growth light intensity was low. The value of maximum net photosynthetic rate （Pmax） in 12.5% daylight decreased to 71.4% of the fully open site. Also the other photosynthetic indexes were accordingly adjusted. In low light, lamina mass per unit area （LMA）, Chla/Chlb, Car/Ch1, light saturation point （LSP）, light compensation point （LCP） decreased while the content of chlorophyll increased comparing with normal light. Under natural sunlight, the number of the thylakoid per granum and the extent of grana stacks increased steadily. On the contrary, the volume of chloroplast granas enlarged, the number of which gradually decreased, and the grana lamella were bad-developed as the light intensity lowered. Meanwhile, Fv/Fm, qP, NPQ, actual photochemical efficiency of PSⅡ showed decrease curve as the light intensity lowered. [Conclusion] The traits of photosynthesis and chlorophyll fluorescence dynamics are very different at different light intensities. In low light, especially in severe stress of 12.5% daylight, the photosynthesis of Catharanthus roseus leaves was badly inhibited, mainly showed the decrease of ΦpsⅡ, qP and NPQ, which affected the development of the photosynthetic organs, the photosynthetic capacity declined and normal growth inhibited.