Comparison of photosynthetic and fluorscence characteristics of leaves in Taxus cuspidata under different light intensities

To further explain acclimation in Taxus cuspidata to light intensity,taking 15-year-old saplings in T.cuspidata as materials,photosynthetic and chloropphyll fluorescence characteristics were studied under different light intensities.The results showed that compared with the salings in T.cuspidata planted in full light,the leaves planted in weak light had lower photosynthetic rate,which was 60% of the value of leaves planted in full light,and lower carboxylation efficiency,so they had the characteristics in shade leaves.Actual photochemical efficiency(ΦPSⅡ),electron transport rate(ETR)and non-photochemical quenching(NPQ) had significant differences between the leaves in weak light and full light,when light intensities was transferred from weak to strong.As light intensity increasing,decreased range of ΦPSⅡof leaves in weak light was higher,ETR of leaves in weak light was lower than that in full light.NPQ of leaves in weak light and full light was increased with light intensity rising,but the index of leaves in weak light could reach the peak value under lower light intensity.Leaves in weak light had higher chlorophyll content,lower ratio of Chl a to Chl b,and lower ETR and ΦPSⅡ,indicating their shade-environmental acclimation.Lower photosynthetic rate and excess light energy dissipation ability in leaves in weak light were the main reason of serious photo inhibition after transferred to strong light.