Lemaître Thomas, Gaufichon Laure, Boutet-Mercey Stéphanie, Christ Aurélie, Masclaux-Daubresse Céline
Unité de Nutrition Azotée des Plantes, UNAP, UR511, INRA, Route de Saint Cyr, F-78000 Versailles, France.
Plant Cell Physiol. 2008 Jul;49(7):1056-65. doi: 10.1093/pcp/pcn081. Epub 2008 May 28.
Adaptation to steady-state low-nutrient availability was investigated by comparing the Wassileskija (WS) accession of Arabidopsis thaliana grown on 2 or 10 mM nitrate. Low nitrogen conditions led to a limited rosette biomass and seed yield. The latter was mainly due to reduced seed number, while seed weight was less affected. However, harvest index was lower in high nitrate compared with limited nitrate conditions. Under nitrogen-limiting conditions, nitrate reductase activity was decreased while glutamine synthetase activity was increased due to a higher accumulation of the cytosolic enzyme. The level of nitrogen remobilization to the seeds was higher under low nitrogen, and the vegetative parts of the plants remaining after seed production stored very low residual nitrogen. Through promoting nitrogen remobilization and recycling pathways, nitrogen limitation modified plant and seed compositions. Rosette leaves contained more sugars and less free amino acids when grown under nitrogen-limiting conditions. Compared with high nitrogen, the levels of proline, asparagine and glutamine were decreased. The seed amino acid composition reflected that of the rosette leaves, thus suggesting that phloem loading for seed filling was poorly selective. The major finding of this report was that together with decreasing biomass and yield, nitrogen limitation triggers large modifications in vegetative products and seed quality.
通过比较在2 mM或10 mM硝酸盐条件下生长的拟南芥Wassileskija（WS）生态型，研究了其对稳态低养分可用性的适应性。低氮条件导致莲座叶生物量和种子产量有限。后者主要是由于种子数量减少，而种子重量受影响较小。然而，与有限硝酸盐条件相比，高硝酸盐条件下的收获指数较低。在氮限制条件下，硝酸还原酶活性降低，而谷氨酰胺合成酶活性增加，这是由于胞质酶的积累增加所致。低氮条件下向种子的氮再利用水平较高，种子生产后剩余的植物营养部分储存的残余氮非常低。通过促进氮再利用和循环途径，氮限制改变了植物和种子的组成。在氮限制条件下生长时，莲座叶含有更多的糖和更少的游离氨基酸。与高氮相比，脯氨酸、天冬酰胺和谷氨酰胺的水平降低。种子氨基酸组成反映了莲座叶的组成，因此表明种子充实的韧皮部装载选择性较差。本报告的主要发现是，除了生物量和产量下降外，氮限制还会引发营养产物和种子质量的重大变化。
