Department of Plant Biology, University of California, 94720, Berkeley, CA, USA.
Planta. 1990 Jun;181(3):399-405. doi: 10.1007/BF00195894.
The effects of phosphorus nutrition on various aspects of photosynthetic metabolism have been examined for soybean plants (Glycine max) grown in growth chambers. Orthophosphate was supplied at two levels in 0.5-strength Hoagland's solution. At the end of the 19-d growth period, plants grown at 10 μM KH2PO4 (low-P plants) had undergone a 40% drop in net CO2 exchange (averaged over a 16-h light period), as compared with control plants grown with 200 μM KH2PO4. Low-P resulted in reductions in the initial activities of five, and in the total activities of seven, Calvin-cycle enzymes. Notable exceptions were the initial and total activities of chloroplastic fructose-1,6-bisphosphatase (EC 3.1.3.11) which were increased by 85 and 53%, respectively, by low-P. Low-P decreased leaf 3-phosphoglycerate (PGA) levels most (by 80%), ribulose-1,5-bis-phosphate (RuBP) less (by 47%) while triose-phosphate (TP) was not significantly changed. The results indicate that photosynthetic CO2-fixation in low-P plants was limited more by RuBP regeneration than by ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) activity. Ribulose-1,5-bisphosphate regeneration in low-P plants did not appear to be limited by ATP and-or NADPH supply because ATP/ADP and NADPH/ NADP(+) ratios were increased by 60 and 37%, respectively, by low-P, and because TP/PGA ratios were higher in low-P plants. Low-P may diminish RuBP regeneration, and hence photosynthesis, by reducing Calvin-cycle enzyme activity, in particular, the initial activity of ribulose-5-phosphate kinase (EC 2.7.1.19) (44% reduction), and by enhancing the flux of carbon into starch biosynthesis.
在生长室中种植的大豆（Glycine max）植株中，研究了磷营养对光合作用代谢各个方面的影响。在 0.5 倍强度的 Hoagland 溶液中，以两种浓度供应正磷酸盐。在 19 天的生长期结束时，与用 200 μM KH2PO4 生长的对照植物相比，在 10 μM KH2PO4 下生长的（低磷）植物的净 CO2 交换量下降了 40％（平均在 16 小时的光照期内）。低磷导致五种卡尔文循环酶的初始活性降低，七种酶的总活性降低。值得注意的例外是叶绿体果糖-1,6-二磷酸酶（EC 3.1.3.11）的初始和总活性分别增加了 85％和 53％。低磷使叶片 3-磷酸甘油酸（PGA）水平降低最多（降低了 80％），核酮糖-1,5-二磷酸（RuBP）降低较少（降低了 47％），而三磷酸（TP）则没有明显变化。结果表明，低磷植物的光合作用 CO2固定受到 RuBP 再生的限制大于核酮糖-1,5-二磷酸羧化酶/加氧酶（EC 4.1.1.39）活性的限制。低磷植物的 RuBP 再生似乎不受 ATP 和/或 NADPH 供应的限制，因为低磷使 ATP/ADP 和 NADPH/NADP（+）的比值分别增加了 60％和 37％，并且低磷植物的 TP/PGA 比值更高。低磷可能通过降低 Calvin 循环酶活性，特别是通过降低核酮糖-5-磷酸激酶（EC 2.7.1.19）的初始活性（降低 44％），以及通过增强碳进入淀粉生物合成的通量，从而减少 RuBP 再生，进而减少光合作用。
