Effects of light intensities on leaf structure and photosynthetic characteristics of yam
In order to investigate the adaptive mechanism of yam to varying light conditions,the yam culti-var'Dahechangyu'was selected as the experimental material.The morphological structure,tissue struc-ture,ultrastructure,photosynthetic characteristics,photosynthetic products,and expression of light re-sponse genes in leaves was investigated respectively under different light intensities.The results indicate that:(1)Decreasing light intensity led to an increase in the light absorption area and capacity of yam by expanding leaf area and chlorophyll content,resulting in a looser leaf structure,smaller cell size,and in-creased number of thylakoid substrate lamellae.(2)Leaf photosynthetic rate(Pn)and transpiration rate(Tr)significantly decreased under 55％-70％shading,along with reductions in starch and soluble sugar con-tents.However,the influence of low light conditions on photosynthesis was mitigated by enhancing the phosphoenolpyruvate carboxylase(PEPC)activity and elevating the CO2 assimilation rate in leaves.(3)The expression levels of DA1,TCP-1,TOR-1,and TOR-2 markedly increased under 55％-70％shading.DA1 and TOR-2 expression levels positively correlated with leaf area and thickness,thereby facilitating leaf enlarge-ment and thickening in yam,and enhancing light energy utilization.In conclusion,yam adjusts its leaf structure characteristics to capture more light energy under different light intensities,under low light inten-sity,the photosynthetic characteristics and expression of photoresponsive genes were altered to accli-mate to various light environments.The findings offered a theoretical foundation for understanding the re-sponse mechanism of yam leaves under varying light intensities.
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