Hughes Nicole M, Morley Christianna B, Smith William K
Department of Biology, Wake Forest University, Winston-Salem, North Carolina 27106 USA.
Liberal Studies Department, Dartmouth College, Hanover, New Hampshire 03755 USA.
New Phytol. 2007;175(4):675-685. doi: 10.1111/j.1469-8137.2007.02133.x.
Juvenile leaves in high-light environments commonly appear red as a result of anthocyanin pigments, which play a photoprotective role during light-sensitive ontogenetic stages. The loss of anthocyanin during leaf development presumably corresponds to a decreased need for photoprotection, as photosynthetic maturation allows leaves to utilize higher light intensities. However, the relationship between photosynthetic development and anthocyanin decline has yet to be quantitatively described. In this study, anthocyanin concentration was measured against photopigment content, lamina thickness, anatomical development, and photosynthetic CO(2) exchange in developing leaves of three deciduous tree species. In all species, anthocyanin disappearance corresponded with development of c. 50% mature photopigment concentrations, c. 80% lamina thickness, and differentiation of the mesophyll into palisade and spongy layers. Photosynthetic gas exchange correlated positively with leaf thickness and chlorophyll content, and negatively with anthocyanin concentration. Species with more rapid photosynthetic maturation lost anthocyanin earliest in development. Chlorophyll a/b ratios increased with leaf age, and were lower than those of acyanic species, consistent with a shading effect of anthocyanin. These results suggest that anthocyanin reassimilation is linked closely with chloroplast and whole-leaf developmental processes, supporting the idea that anthocyanins protect tissues until light processing and carbon fixation have matured to balance energy capture with utilization.
在高光环境下，幼叶通常因花青素色素而呈现红色，花青素在光敏感的个体发育阶段发挥光保护作用。叶片发育过程中花青素的丧失大概对应着对光保护需求的降低，因为光合成熟使叶片能够利用更高的光照强度。然而，光合发育与花青素减少之间的关系尚未得到定量描述。在本研究中，针对三种落叶树种发育叶片中的光合色素含量、叶片厚度、解剖结构发育以及光合二氧化碳交换，测定了花青素浓度。在所有树种中，花青素的消失与约50%成熟光合色素浓度的发育、约80%叶片厚度的发育以及叶肉分化为栅栏层和海绵层相对应。光合气体交换与叶片厚度和叶绿素含量呈正相关，与花青素浓度呈负相关。光合成熟较快的树种在发育过程中最早失去花青素。叶绿素a/b比值随叶龄增加，且低于无花青素树种，这与花青素的遮光效应一致。这些结果表明，花青素的再同化与叶绿体和全叶发育过程密切相关，支持了花青素在光处理和碳固定成熟以平衡能量捕获与利用之前保护组织的观点。
