Department of Agronomy, Purdue University, West Lafayette, Indiana 47907.
Plant Physiol. 1986 Feb;80(2):454-8. doi: 10.1104/pp.80.2.454.
The objective of this study was to identify factors which limit leaf nitrate reductase (NR) activity as decline occurs during flowering and beginning seed development in soybean (Glycine max [L.] Merr. cv Clark). Level of NR enzyme activity, level of reductant, and availability of NO(3) (-) as substrate were evaluated for field-grown soybean from flowering through leaf senescence. Timing of reproductive development was altered within one genotype by (a) exposure of Clark to an artificially short photoperiod to hasten flowering and podfill, and (b) the use of an early flowering isoline. Nitrogen (N) was soil-applied to selected plots at 500 kilograms per hectare as an additional variable. Stem NO(3) (-) concentration and in vivo leaf NR activity were significantly correlated (R(2) = 0.69 with nitrate in the assay medium and 0.74 without nitrate in the medium at P = 0.001) across six combinations of reproductive and soil N-treatment. The supply of NO(3) (-) from the root to the leaf tissue was the primary limitation to leaf NR activity during flowering and podfill. Levels of NR enzyme and reductant were not limiting to leaf NR activity during this period.
本研究旨在确定在大豆（Glycine max [L.] Merr. cv Clark）开花和种子发育初期叶片硝酸还原酶（NR）活性下降时限制其活性的因素。从开花到叶片衰老，对田间生长的大豆的 NR 酶活性水平、还原剂水平以及作为底物的 NO₃(-)的可用性进行了评估。通过（a）将 Clark 暴露于人为缩短的光照周期以加速开花和荚果填充，以及（b）使用早开花的等位基因系，改变了一个基因型的生殖发育时间。将氮（N）以每公顷 500 公斤的量作为附加变量施用于选定的地块。茎中 NO₃(-)浓度和活体叶片 NR 活性在六个生殖和土壤 N 处理组合中呈显著相关（在 0.001 水平下，在测定介质中有硝酸盐时 R²=0.69，无硝酸盐时 R²=0.74）。从根部向叶片组织供应 NO₃(-)是开花和荚果填充期间叶片 NR 活性的主要限制因素。在这段时间内，NR 酶和还原剂的水平并没有限制叶片 NR 活性。
