Abstract：
We hypothesized that anthocyanins act as a sugar-buffer and an alternative electron sink during leaf senescence to prevent sugar-mediated early senescence and photoinhibition. To elucidate the role of anthocyanin, we monitored seasonal changes in photosynthetic traits, sugar, starch and N contents, pigment composition, and gene expression profiles in leaves exposed to substantially different light conditions within a canopy of an adult fullmoon maple (Acer japonicum) tree. Enhancement of starch amylolysis accompanied by cessation of starch synthesis occurred in the same manner independent of light conditions. Leaf sugar contents increased, but reached upper limits in the late stage of leaf senescence, even though leaf anthocyanins further increased after complete depletion of starch. Sun-exposed leaves maintained higher energy consumption via electron flow than shade-grown leaves during leaf N resorption. Thus, anthocyanins accumulated in sun-exposed leaves might have a regulative role as a sugar-buffer, retarding leaf senescence, and an indirect photoprotective role as an alternative sink for electron consumption to compensate declines in other metabolic processes such as starch and protein synthesis. In this context, anthocyanins may be key substrates protecting both outer-canopy leaves (against photoinhibition) and inner-canopy leaves (via shading by outer-canopy leaves) from high light stress during N resorption.
摘要：
我们假设花青素在叶片衰老过程中充当糖缓冲剂和替代电子汇，以防止糖介导的早期衰老和光抑制。为了阐明花青素的作用,我们监测了光合性状的季节性变化，糖,淀粉和N含量，颜料成分,和成年满月枫树（Acerjaponicum）树冠内暴露于完全不同的光照条件下的叶片中的基因表达谱。淀粉淀粉分解的增强伴随着淀粉合成的停止以相同的方式发生，而与光照条件无关。叶片含糖量增加，但在叶片衰老后期达到了上限，尽管叶花色苷在淀粉完全耗尽后进一步增加。在叶片N吸收过程中，暴露于阳光的叶片通过电子流保持了更高的能量消耗。因此，在阳光照射的叶子中积累的花青素可能具有作为糖缓冲的调节作用，延缓叶片衰老，以及作为电子消耗替代汇的间接光保护作用，以补偿淀粉和蛋白质合成等其他代谢过程的下降。在这种情况下，花青素可能是保护外冠层叶（抗光抑制）和内冠层叶（通过外冠层叶遮荫）免受氮吸收过程中高光胁迫的关键底物。
