Fondy B R, Geiger D R
Department of Biology, Seton Hill College, Greensburg, Pennsylvania 15601.
Plant Physiol. 1985 Aug;78(4):753-7. doi: 10.1104/pp.78.4.753.
Storage of newly fixed carbon as starch and sucrose follows a regular daily pattern in exporting sugar beet leaves under constant day length and level of illumination. Up to the final two hours of the light period, when starch storage declines, a nearly constant proportion of newly fixed carbon was allocated to carbohydrate storage, principally starch. Sucrose is stored only early in the light period, when there is little accumulation of starch. Pulse labeling with (14)CO(2) revealed that considerable starch synthesis was taking place at this time. Starch made the previous day was not mobilized during this period but breakdown of newly synthesized starch may occur when carbon flow into sucrose synthesis increases early in the day. At the end of the day, starch storage declined from the constant level observed during most of the day, but no diversion of label into export of specific alternative compounds could be detected. Lowered storage of starch persisted when the 14-hour light period was lengthened. Changed allocation of recently fixed carbon to sucrose and starch at the beginning and end of the light period was not the result of outright inactivation of pathways but of regulation of carbon flow.
在光照时长和光照强度恒定的条件下，新固定的碳以淀粉和蔗糖的形式储存，这在甜菜叶片的糖分输出过程中呈现出规律的每日模式。在光照期的最后两小时之前，淀粉储存量下降，新固定的碳中几乎恒定比例的碳被分配到碳水化合物储存中，主要是淀粉。蔗糖仅在光照期早期储存，此时淀粉积累较少。用（14）CO₂ 进行脉冲标记显示，此时正在进行大量的淀粉合成。前一天合成的淀粉在此期间并未被调动，但当天早些时候当碳流入蔗糖合成增加时，新合成的淀粉可能会发生分解。在一天结束时，淀粉储存量从一天中大部分时间观察到的恒定水平下降，但未检测到标记物转向特定替代化合物的输出。当光照期延长至14小时时，淀粉储存量持续降低。在光照期开始和结束时，新固定的碳分配到蔗糖和淀粉中的变化并非是途径完全失活的结果，而是碳流调节的结果。
