Pate J S, Atkins C A
Department of Botany, University of Western Australia, Nedlands, W. A. 6009, Australia.
Plant Physiol. 1983 Apr;71(4):835-40. doi: 10.1104/pp.71.4.835.
Exchanges of CO(2) and changes in content of C and N were studied over the life of a leaf of Lupinus albus L. These data were combined with measurements of C:N weight ratios of xylem (upper stem tracheal) and phloem (petiole) sap to determine net fluxes of C and N between leaf and plant. Phase 1 of leaf development (first 11 days, leaf to one-third area) showed increasing net import of C and N, with phloem contributing 61% of the imported C and 18% of the N. (14)C feeding studies suggested the potential for simultaneous import and export through phloem over the period 9 to 12 days. Phase 2 (11-20 days, leaf attaining maximum area and net photosynthesis rate) exhibited net import through xylem and increasing export through phloem. Eighty-two% of xylem-delivered N was consumed in leaf growth, the remainder exported in phloem. Phase 3 (20-38 days) showed high but declining rates of photosynthesis, translocation, and net export of N. Phase 4 (38-66 days) exhibited substantial losses of N and declining photosynthesis and translocation of C. C:N ratio of xylem sap remained constant (2.3-2.6) during leaf life; petiole phloem sap C:N ratio varied from 25 to 135 over leaf development. The relationships between net photosynthesis and N import in xylem were: phase 1, 4.8 milligrams C per milligram N; phase 2, 24.7 milligrams C per milligram N; phase 3, 91.9 milligrams C per milligram N; and phase 4, 47.7 milligrams C per milligram N.
研究了白羽扇豆（Lupinus albus L.）叶片整个生命周期内的二氧化碳交换以及碳和氮含量的变化。这些数据与木质部（茎上部气管）和韧皮部（叶柄）汁液中碳氮重量比的测量结果相结合，以确定叶片与植株之间碳和氮的净通量。叶片发育的第1阶段（最初11天，叶片面积达到三分之一）显示碳和氮的净输入增加，韧皮部贡献了61%的输入碳和18%的输入氮。¹⁴C饲喂研究表明，在第9至12天期间，韧皮部存在同时进行碳输入和输出的可能性。第2阶段（11 - 20天，叶片达到最大面积和净光合速率）表现为通过木质部的净输入以及通过韧皮部增加的输出。木质部输送的氮中有82%用于叶片生长，其余的通过韧皮部输出。第3阶段（20 - 38天）显示出高但下降的光合作用、转运和氮净输出速率。第4阶段（38 - 66天）表现出大量的氮损失以及碳的光合作用和转运下降。在叶片生命周期中，木质部汁液的碳氮比保持恒定（2.3 - 2.6）；叶柄韧皮部汁液的碳氮比在叶片发育过程中从25变化到135。木质部中净光合作用与氮输入之间的关系为：第1阶段，每毫克氮对应4.8毫克碳；第2阶段，每毫克氮对应24.7毫克碳；第3阶段，每毫克氮对应91.9毫克碳；第4阶段，每毫克氮对应47.7毫克碳。
