Physiological Response to Salinity in Rice Plant : III. A possible mechanism for Na+ exclusion in rice root under NaCl-stress conditions
Physiological Response to Salinity in Rice Plant : III. A possible mechanism for Na+ exclusion in rice root under NaCl-stress conditions
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水稻对盐度的生理反应：III。
DOI：
10.1626/jcs.63.326
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发表时间：
1994
影响因子：
--
通讯作者：
H. Naito
中科院分区：
文献类型：
--
作者：
Mikio Tsuchiya;M. Miyake;H. Naito
以反渗透作为离子排斥原理，研究了NaCl胁迫下水稻根系排斥Na+的机理和品种差异。在静水压力为294和686 kPa的NaCl溶液中，对根切面的分泌物进行了取样。整个切面渗出物的Na+浓度最多比根培养基低60%。然而，柱状茎切面渗出物的Na+浓度比根培养基低约85%。这些结果表明，Na+排斥可能发生在外表皮和内表皮。在静水压力作用下，渗出液中Na+浓度降低，说明Na+排除可能是由蒸腾作用引起的负压驱动的非代谢过程，可能是基于反渗透作用。从x射线显微分析的结果来看，Na+在IR28中穿过内胚层的运动少于KR1。而盐渍条件下，KR1的蒸腾速率更高，这可能与KR1根系的形态特征有关，即单株根系较多，根系较长较粗，茎柱面积与横截面面积之比较高，每横截面血管较多。综上所述，KR1和IR28耐盐性的品种差异与其在盐碱条件下通过保持蒸腾速率来维持离子排除负压的能力差异有关。
The mechanism and varietal difference of Na+ exclusion in rice roots exposed to NaCl stress was studied in relation to reverse osmosis as the principle of ion exclusion. Exudates from the cut-surface of a root exposed to 20 mmoll-1 NaCl solution with hydrostatic pressure of 294 and 686 kPa were sampled. Na+ concentration of the exudate from the whole cut-surface was at most 60% lower than that of the root medium. However, Na+ concentration of the exudate from the cut-surface of the stele was about 85% lower than that of the root medium. These results indicated that Na+ exclusion might occur at the exodermis and endodermis. The decrease of Na+ concentration of the exudate with hydrostatic pressure indicated that Na+ exclusion might be a non-metabolic process which could be driven by negative pressure induced by transpiration, and seemed to be based on reverse osmosis. From the results of X-ray micro-analysis, Na+ movement across the endodermis was less in IR28 than in Kala-Rata 1-24 (KR1). However, transpiration rate under saline conditions was higher in KR1, and it was considered to be supported by morphological characteristics of KR1 root, i.e. more roots per plant, longer and thicker roots, high ratio of stele area to the area of cross-section and more vessels per cross-section. It is concluded that the varietal difference in salt tolerance between KR1 and IR28 is related to the difference in the ability to maintain the negative pressure for ion exclusion by keeping the transpiration rate under saline conditions.