摘要:以海水稻品种‘FL478’‘JX99’‘Pokkali’和盐敏感品种‘IR29’为材料，设置6个土壤含盐量（0 g·kg-1、1 g·kg-1、2 g·kg-1、3 g·kg-1、4 g·kg-1、5 g·kg-1），在防雨大棚下进行盆栽试验，孕穗期测定水稻叶片的丙二醛含量、细胞膜透性、可溶性糖含量、脯氨酸含量，以及Δ1-吡咯啉-5-羧酸合成酶（P5CS）、鸟氨酸-δ-氨基转移酶（δ-OAT）和超氧化物歧化酶（SOD）活性，旨在探讨盐胁迫下海水稻渗透调节物质、抗逆酶与海水稻耐盐性的关系，为海水稻耐盐基因的发掘和耐盐品种的选育提供理论依据。结果表明：1）盐胁迫抑制了海水稻叶绿素的合成与积累，表现为水稻叶片的叶绿素含量随盐胁迫梯度的增加而减少，但其叶绿素含量显著高于盐敏感水稻品种。2）海水稻和盐敏感水稻的可溶性糖对盐胁迫的响应差异显著，其中土壤含盐量0~3 g·kg-1胁迫下，盐敏感水稻叶片的可溶性糖含量的增加显著高于海水稻，但是在土壤含盐量4~5 g·kg-1下，海水稻叶片的可溶性糖积累量显著高于盐敏感水稻品种。3）随盐胁迫加剧海水稻和盐敏感水稻叶片的丙二醛积累，造成细胞膜透性逐渐增大，但是海水稻品种丙二醛的积累量显著低于盐敏感对照，这表明海水稻叶片细胞膜损伤较小。4）盐胁迫下，4个水稻叶片的脯氨酸含量和P5CS、δ-OAT、SOD活性随盐胁迫浓度增加均表现出先升高后降的趋势，海水稻和盐敏感水稻分别在3 g·kg-1、2 g·kg-1盐浓度达到峰值，而海水稻植株的游离脯氨酸积累量、P5CS、δ-OAT和SOD活性显著高于盐敏感水稻。5）盐胁迫下海水稻可溶性糖、脯氨酸和P5CS之间呈极显著正的简单相关和偏相关性。因此，海水稻的抗盐性为生理性耐盐：在盐胁迫下，植株脯氨酸合成酶P5CS和δ-OAT均被激活，脯氨酸合成的两个途径（谷氨酸→脯氨酸和鸟氨酸→脯氨酸）同时增强，促使植株游离脯氨酸的快速积累。同时，由于植株游离脯氨酸快速积累，也助于植株SOD活性的激活，有效降低活性氧的积累，并通过合成可溶性糖与脯氨酸协同缓解渗透胁迫，而表现为较强的耐盐性。
关键词:海水稻/
盐胁迫/
抗逆生理/
渗透调节/
抗逆酶活性
Abstract:The sea rice varieties 'FL478' 'JX99' 'Pokkali' and salt-sensitive variety 'IR29' were used to determine malondialdehyde content, cell membrane permeability, soluble sugar and proline in rice leaf. We also investigated the activities of Δ1-pyrroline-5-carboxylic acid synthetase (P5CS), ornithine-δ-aminotransferase (δ-OAT) and superoxide dismutase (SOD) under 0 g·kg-1, 1 g·kg-1, 2 g·kg-1, 3 g·kg-1, 4 g·kg-1 and 5 g·kg-1 of soil salt treatments at booting stage of potted rice under rainproof greenhouse conditions. This aim of the study was to investigate the relationship between osmotic regulators, stress resistance enzymes and salt tolerance of sea rice under salinity stress. The study also provided theoretical basis for the exploration of salt tolerance genes and breeding sea rice varieties with salt tolerance. The results were as follows:1) salinity stress inhibited the synthesis and accumulation of chlorophyll in rice. Then chlorophyll content in rice leaf decreased with increasing salt stress concentration, and was significantly higher than that of salt-sensitive rice. 2) The response of soluble sugars of sea rice and salt-sensitive rice to salinity stress had significantly differences. The rise in soluble sugars of sea rice was less than that of salt-sensitive rice under 0-3 g·kg-1 soil salt content, but the content of soluble sugars of sea rice was significantly higher than that of salt-sensitive rice under 4-5 g·kg-1 soil salt content. 3) Malondialdehyde contents of sea rice and salt-sensitive varieties increased with increasing salt stress, resulting in increased cell membrane permeability. However, malondialdehyde content of sea rice was significantly lower than that of salt-sensitive rice. This implied that leaf membrane damage of sea rice was significantly less than that of salt-sensitive rice. 4) Proline content and P5CS, δ-OAT and SOD activities of rice leaf increased initially and then decreased with increasing salt stress. Proline content and P5CS, δ-OAT and SOD activities of sea rice and salt-sensitive rice were maximum under 3 g·kg-1 and 2 g·kg-1 salt content, respectively. However, proline content and P5CS, δ-OAT and SOD activities of sea rice were significantly higher than those of salt-sensitive rice. 5) Simple and partial correlations of soluble sugar, proline and P5CS were significantly positive under salinity stress. Salt tolerance characteristics of sea rice were considered as physiological salt tolerance. Proline synthetase P5CS and δ-OAT of sea rice were both activated by salinity stress. The activity of two pathways of proline synthesis (ornithine synthase and glutamate synthase pathways) were simultaneously increased, which promoted rapid and high accumulation of free proline in sea rice. Rapid accumulation of free proline also activated SOD activity, which effectively destroyed the accumulation of intracellular reactive oxygen species. Soluble sugar and proline synergistically alleviated osmotic stress and sea rice showed a strong salt tolerance.
Key words:Sea rice/
Salt stress/
Anti-stress physiology/
Osmotic regulation/
Resistance enzyme activity
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