Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
Plant Physiol. 1987 Sep;85(1):137-44. doi: 10.1104/pp.85.1.137.
When arrival of shoot supplied carbohydrate to the nodulated root system of soybean was interrupted by stem girdling, stem chilling, or leaf removal, nodule carbohydrate pools were utilized, and a marked decline in the rates of CO(2) and H(2) evolution was observed within approximately 30 minutes of treatment. Nodule excision studies demonstrated that the decline in nodulated root respiration was associated with nodule rather than root metabolism, since within 3.5 hours of treatment, nodules respired at less than 10% of the initial rates. Apparently, a continuous supply of carbohydrate from the shoot is required to support nodule, but not root, function. Depletion of nodular carbohydrate pools was sufficient to account for the (diminishing) nodule respiration of girdled plants. Of starch and soluble sugar pools within the whole plant, only leaf starch exhibited a diurnal variation which was sufficient to account for the respiratory carbon loss of nodules over an 8 hour night. Under 16 hour nights, or in continuous dark, first the leaf starch pools were depleted, and then nodule starch reserves declined concomitant with a decrease in the rates of CO(2) and H(2) evolution from the nodules. Nodule soluble sugar levels were maintained in dark treated plants but declined in girdled plants. The depletion of starch in root nodules is an indicator of carbohydrate limitation of nodule function.
当大豆根瘤系统的供氮碳水化合物供应被茎环割、茎冷处理或叶片去除中断时,根瘤碳水化合物库被利用,并且在处理后约 30 分钟内观察到 CO(2)和 H(2)演化的速率显著下降。根瘤切除研究表明,根瘤呼吸的下降与根瘤而不是根代谢有关,因为在处理后 3.5 小时内,根瘤的呼吸速率不到初始速率的 10%。显然,需要从地上部分连续供应碳水化合物来支持根瘤,但不是根的功能。根瘤碳水化合物库的耗尽足以解释环割植物的(减少的)根瘤呼吸。在整个植株的淀粉和可溶性糖库中,只有叶片淀粉表现出昼夜变化,足以解释 8 小时夜间根瘤呼吸的碳损失。在 16 小时的夜间或连续黑暗中,首先耗尽叶片淀粉库,然后根瘤淀粉储备下降,同时根瘤的 CO(2)和 H(2)演化速率下降。黑暗处理的植物中根瘤的可溶性糖水平保持不变,但在环割植物中下降。根瘤淀粉的耗尽是根瘤功能碳水化合物限制的指标。