Communication mechanisms between root and shoot in the reduction of photosynthesis during senescence in crop plants under water stress

水分胁迫下作物衰老过程中光合作用减少的根冠通讯机制

基本信息

批准号：
11460007
负责人：
HIRASAWA Tadashi
金额：
$ 9.02万
依托单位：
Tokyo University of Agriculture and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

In order to clarify the mechanism of the reduction in photosynthesis during senescence under water stress with reference to root-shoot relations, we investigated photosynthetic rate, content of ribulose-1, 5-bisphosphate carboxylase/oxygenase (Rubisco), which is, a key enzyme of the rate of photosynthesis, and the expression of Rubisco genes during senescence under various conditions.1. There were close correlations among Rubisco content and the abundances of rbcL and rbcS (genes encoding the large subunit and small subunit of Rubisco, respectively) mRNA of a leaf during the reduction of photosynthetic rate due to senescence.2. Partitioning of nitrogen decreased to leaves and increased to roots under deficient soil moisture conditions, causing the reduction of leaf nitrogen content and, therefore, photosynthetic rate.3. There were close correlations among nitrogen content and the abundances of rbcL and rbcS mRNA of a leaf during senescence and the nitrogen topdressing increased their abundances.4. When plants were treated with exogenous cytokinin, nitrogen content and the abundances of rbcL and rbcS mRNA of a leaf increased without the increase in total nitrogen content of a plant, suggesting that cytokinin might increase the partitioning of nitrogen to leaves.5. The activity of cytokinin transported from root to shoot decreased in plants grown under deficient soil moisture conditions.From these results, it was suggested that one of the causal factors in the significant reduction of photosynthetic rate under deficient soil moisture conditions might be the reduction of leaf nitrogen content due to smaller partitioning of leaf nitrogen to leaves and that the levels of cytokinin transported from root to shoot might affect the leaf nitrogen content by changing the nitrogen partitioning.

为了阐明水分胁迫下衰老过程中光合作用减少的机制，结合根冠关系，我们研究了光合作用速率、核酮糖-1, 5-二磷酸羧化酶/加氧酶（Rubisco）的含量，这是光合作用的关键。不同条件下衰老过程中光合作用酶和Rubisco基因表达的变化。 1．在衰老导致的光合速率降低过程中，Rubisco含量与叶片rbcL和rbcS（分别编码Rubisco大亚基和小亚基的基因）mRNA丰度存在密切相关。2．土壤水分不足时，氮素向叶片的分配减少，向根部的分配增加，导致叶片氮含量降低，光合速率降低。3．叶片衰老过程中氮含量与rbcL、rbcS mRNA丰度存在密切相关，追施氮肥可提高其丰度。 4．外源细胞分裂素处理植物后，叶片的氮含量以及rbcL和rbcS mRNA丰度增加，但总氮含量没有增加，这表明细胞分裂素可能增加了氮在叶片中的分配。 5．在土壤水分不足的条件下生长的植物中，从根部运输到地上部的细胞分裂素的活性降低。从这些结果表明，土壤水分不足的条件下光合速率显着降低的原因之一可能是叶片的减少。由于叶氮到叶片的分配较小而导致氮含量增加，并且从根部转运到地上部的细胞分裂素水平可能通过改变氮分配来影响叶片氮含量。