Wittenbach V A
Central Research and Development Department, E. I. du Pont de Nemours and Co., Experimental Station, Wilmington, Delaware 19898.
Plant Physiol. 1983 Sep;73(1):121-4. doi: 10.1104/pp.73.1.121.
Well nodulated, field-grown soybeans (Glycine max [L.] Merr. var Williams) were depodded just prior to seed development and near mid pod-fill. Both treatments caused a considerable increase in leaf dry weight, suggesting continued photosynthate production following pod removal. Moreover, depodding had a marked effect on leaf soluble protein without affecting total proteolytic activity. Early depodding caused a 50% increase in leaf protein, and both early and late depodding caused the retention of protein for several weeks following the decline in control leaves. But despite this retention of protein, leaves of depodded plants showed no difference in the onset of the irreversible decline in photosynthesis. Therefore, although depodding delayed the loss of leaf chlorophyll and protein, it did not delay the onset of functional leaf senescence and in fact, actually appeared to enhance the rate of decline in photosynthesis. There was a good correlation between the irreversible decline in ribulose bisphosphate carboxylase (activity and amount) and that of photosynthesis. In contrast, the correlation did not seem as good between stomatal closure and the onset of the irreversible decline in photosynthesis. The reason total soluble protein remained high following depodding while carboxylase, which normally comprised 40% of the soluble protein, declined was because several polypeptides increased in amounts sufficient to offset the loss of carboxylase. This change in leaf protein composition indicates a change in leaf function; this is discussed in terms of other recent findings.
在种子发育前期和豆荚充实中期前后，将结瘤良好、田间种植的大豆（Glycine max [L.] Merr. var Williams）的豆荚摘除。两种处理均使叶片干重显著增加，这表明摘除豆荚后光合作用产物仍在持续产生。此外，摘除豆荚对叶片可溶性蛋白有显著影响，但不影响总蛋白水解活性。早期摘除豆荚使叶片蛋白增加了50%，早期和晚期摘除豆荚均使叶片在对照叶片蛋白含量下降后的数周内仍保留较高蛋白含量。但是，尽管蛋白得以保留，摘除豆荚植株的叶片在光合作用不可逆下降的起始时间上并无差异。因此，尽管摘除豆荚延迟了叶片叶绿素和蛋白的损失，但并未延迟叶片功能衰老的起始，实际上，似乎还加快了光合作用的下降速率。核酮糖二磷酸羧化酶（活性和含量）的不可逆下降与光合作用的不可逆下降之间存在良好的相关性。相比之下，气孔关闭与光合作用不可逆下降起始之间的相关性似乎没那么好。摘除豆荚后总可溶性蛋白含量仍然较高，而通常占可溶性蛋白40%的羧化酶含量下降，原因是几种多肽的含量增加，足以抵消羧化酶的损失。叶片蛋白组成的这种变化表明叶片功能发生了改变；结合其他近期研究结果对此进行了讨论。
