Department of Plant and Soil Biology, University of California, Berkeley, California 94720.
Plant Physiol. 1990 Jan;92(1):29-36. doi: 10.1104/pp.92.1.29.
The effect of low phosphate supply (low P) was determined on the diurnal changes in the rate of carbon export, and on the contents of starch, sucrose, glucose, and fructose 2,6-bisphosphate (F2,6BP) in leaves. Low-P effects on the activities of a number of enzymes involved in starch and sucrose metabolism were also measured. Sugar beets (Beta vulgaris L. cv. F58-554H1) were cultured hydroponically in growth chambers and the low-P treatment induced nutritionally. Low-P treatment decreased carbon export from the leaf much more than it decreased photosynthesis. At growth chamber photon flux density, low P decreased carbon export by 34% in light; in darkness, export rates fell but more so in the control so that the average rate in darkness was higher in low-P leaves. Low P increased starch, sucrose, and glucose contents per leaf area, and decreased F2, 6BP. The total extractable activities of enzymes involved in starch and sucrose synthesis were increased markedly by low P, e.g. adenosine 5-diphosphoglucose pyrophosphorylase, cytoplasmic fructose-1,6-bisphosphatase, uridine 5-diphosphoglucose pyrophosphorylase, and sucrose-phosphate synthase. The activities of some enzymes involved in starch and sucrose breakdown were also increased by low P. We propose that plants adapt to low-P environments by increasing the total activities of several phosphatases and by increasing the concentrations of phosphate-free carbon compounds at the expense of sugar phosphates, thereby conserving Pi. The partitioning of carbon among the various carbon pools in low-P adapted leaves appears to be determined in part by the relative capacities of the enzymes for starch and sucrose metabolism.
低磷供应（低 P）对叶片中碳输出率的日变化以及淀粉、蔗糖、葡萄糖和果糖 2,6-二磷酸（F2,6BP）含量的影响进行了确定。还测量了低 P 对参与淀粉和蔗糖代谢的一些酶活性的影响。在生长室中用水培法培养了甜菜（Beta vulgaris L. cv. F58-554H1），并进行了营养诱导的低 P 处理。低 P 处理使叶片从光合作用中吸收的碳量减少，而不是光合作用本身。在生长室的光子通量密度下，低 P 在光照下使碳输出减少了 34%；在黑暗中，出口率下降，但在对照中下降得更多，因此低 P 叶片在黑暗中的平均出口率更高。低 P 增加了每叶面积的淀粉、蔗糖和葡萄糖含量，并降低了 F2,6BP。低 P 显著增加了参与淀粉和蔗糖合成的酶的总可提取活性，例如腺苷二磷酸葡萄糖焦磷酸化酶、细胞质果糖-1,6-二磷酸酶、尿苷二磷酸葡萄糖焦磷酸化酶和蔗糖磷酸合酶。参与淀粉和蔗糖分解的一些酶的活性也被低 P 增加。我们提出，植物通过增加几种磷酸酶的总活性并增加磷酸根免费碳化合物的浓度来适应低 P 环境，从而节省 Pi。在低 P 适应叶片中，碳在各种碳库之间的分配似乎部分取决于酶对淀粉和蔗糖代谢的相对能力。
