Munier-Jolain Nathalie, Salon Christophe
INRA, Unité de Génétique et d'Ecophysiologie des Légumineuses, BP 86510, F-21065 Dijon Cedex, France.
J Exp Bot. 2003 Nov;54(392):2457-65. doi: 10.1093/jxb/erg266. Epub 2003 Sep 25.
The composition of the translocates reaching the seeds of pea plants having various nitrogen (N) nutrition regimes was investigated under field situations. Sucrose flow in the phloem sap increased with the node number, but was not significantly different between N nutrition levels. Because N deficiency reduced the number of flowering nodes and the number of seeds per pod, the sucrose flow bleeding from cut peduncles was divided by the number of seeds to give the amount of assimilates available per seed. The sucrose concentration in phloem sap supplied to seeds at the upper nodes was higher than that at the lower nodes. The flow of sucrose delivered to the seeds during the cell division period was correlated with seed growth potential. Seeds from the more N-stressed plants had both the highest seed growth rate and received a higher sucrose flux per seed during the cell division period. As seed growth rate is highly correlated with the number of cotyledonary cells produced during the cell division period, sucrose flow in phloem sap is proposed to be an important determinant of mitotic activity in seed embryos. The carbon (C)/N ratio of the flow of translocates towards seeds was higher under conditions of N-deficiency than with optimal N nutrition, indicating that N flux towards seeds, in itself, is not the main determinant of seed growth potential.
在田间条件下，研究了处于不同氮（N）营养状况的豌豆植株输送到种子中的易位物质的组成。韧皮部汁液中的蔗糖流量随节数增加，但在不同氮营养水平之间没有显著差异。由于氮缺乏会减少开花节数和每荚种子数，因此将从切断的花梗中渗出的蔗糖流量除以种子数，得出每粒种子可利用的同化物量。供应给上部节位种子的韧皮部汁液中的蔗糖浓度高于下部节位。细胞分裂期输送到种子的蔗糖流量与种子生长潜力相关。来自氮胁迫更严重植株的种子，在细胞分裂期具有最高的种子生长速率，并且每粒种子获得的蔗糖通量更高。由于种子生长速率与细胞分裂期产生的子叶细胞数量高度相关，因此韧皮部汁液中的蔗糖流量被认为是种子胚有丝分裂活性的重要决定因素。在氮缺乏条件下，向种子输送的易位物质的碳（C）/氮比率高于最佳氮营养条件，这表明向种子的氮通量本身并不是种子生长潜力的主要决定因素。
