Regulation of Diurnal Carbohydrate Reserves and Translocation

昼夜碳水化合物储备为叶片在夜间和低光合作用时期提供碳输出，从而维持不间断的碳供应给非光合作用的植物结构，用于生长、储存和代谢。在一些植物中，如甜菜和大豆，每日储备以淀粉的形式存在，而在其他植物中，如蚕豆和菠菜，蔗糖会积累。我们项目的目标是系统地确定(1)蔗糖和淀粉的碳分配以及出口是如何被调节的，以一种方式为叶片提供昼夜碳水化合物储备，并调节当前在昼夜循环中的出口速度；(2)光合作用的碳同化，当出口受到限制或光合作用增加时，碳分配和出口相互作用，在积累蔗糖和不积累蔗糖的植物中都是如此。我们将测量通过延长白天或缩短前一夜来改变碳分配时两种植物叶片的出口率、酶活性和代谢物水平的变化。在蔗糖贮藏和淀粉贮藏植物中，通过低温诱导的减缓接收器官代谢限制出口或通过提高CO2来增加光合作用对光合作用和碳水化合物积累的影响进行比较。

Diurnal carbohydrate reserves provide leaves with carbon for export at night and during times of low photosynthesis, thereby maintaining an uninterrupted supply of carbon to non- photosynthesizing plant structures for growth, storage and metabolism. In some plants, like sugar beet and soybean, the diurnal reserve takes the form of starch, while in other plants, like fava bean and spinach, sucrose accumulates. The objectives of our program are to identify systematically (1) how carbon apportionment to sucrose and starch and of export together are regulated in a way that furnishes a diurnal carbohydrate reserve to leaves and regulates the current rate of export throughout the day- night cycle and (2) how photosynthetic carbon assimilation, carbon allocation and export interact when export is restricted or photosynthesis is increased, both in plants that accumulate sucrose and those that do not. We will measure changes in export rates, enzyme activities and metabolite levels in leaves of the two types of plants when carbon allocation is changed by extending the day or shortening the previous night. The ways in which restricting export by chilling-induced slowing of metabolism in the receiving organs or of increasing photosynthesis by raising CO2 affects photosynthesis and carbohydrate accumulation will be compared in sucrose-storing and starch storing plants.