Response Of Photosynthetic Physiological Characteristics Of Japanese Yew Seedlings To Different Light Conditions

In order to investigate the response characteristics of Japanese yew seedlings in different ages to different light conditions, Japanese yew seedlings in different ages (three years old and five years old) were taken as experimental materials to study the photosynthetic physiological characteristics under four light conditions, i.e. FL:full light; LI:50%FL; L2:30%FL; L3:15%FL. The results were showed as follows:Full light declined the contents of chlorophyll a, chlorophyll b and total chlorophyll for two seedling age seedlings. The value of chlorophyll a/b of Japanese yew seedlings for two seedling age seedlings under shade conditions were greater than that under full light condition. Compared five-year-old seedlings with three-year-old seedlings, chlorophyll content presented a rising trend.In the light response curves of photosynthesis of Japanese yew seedlings for two seedling age seedlings under FL condition, the net photosynthetic rate (Pn) declined after Pn reaching the maximum follow photosynthetically active radiation (PAR) enhanced. The decline range of Pn of the five-year-old seedlings was less than that of the three-year-old seedlings. The trends of light response curve of photosynthesis of Japanese yew seedlings for two seedling age seedlings were basically consistent under three shade conditions. The light response parameters of the five-year-old seedlings were slightly better than that of the three-year-old seedlings.The trends of response curves of intercellular CO2concentration of Japanese yew seedlings for two seedling age seedlings under four light conditions. The intercellular CO2concentration decreased rapidly from the highest point of400μmol/mol follow PAR enhanced. Compared with three shade conditions, the decline range of intercellular CO2concentration was the biggest for two seedling age seedlings under full light condition.Compared with three shade conditions, the stomatal conductance (Gs) of Japanese yew seedlings was the minimum for two seedling age seedlings under full light condition.Compared with shade conditions, the fluorescence parameters basis fluorescence (F0) and non-photochemical quenching coefficient (qN) of Japanese yew seedlings were larger for two seedling age seedlings under full light condition. On the contrary, the maximum fluorescence (Fm), variable fluorescence (Fv), potential activity of PS Ⅱ (Fv/F0) and the efficiency of solar energy conversion (Fv/Fm) were smaller. Compared with shade conditions, the photochemical quenching coefficient (qP) and the electron transport rate (ETR) of Japanese yew seedlings were also slightly lower for two seedling age seedlings under full light condition.Compared with shade conditions, the activities of superoxide dismutase (SOD) and peroxidase (POD) of Japanese yew seedlings were higher for two seedling age seedlings under full light condition.Compared with shade conditions, the malondialdehyde content (MDA) of Japanese yew seedlings were higher for two seedling age seedlings under full light condition.