镉胁迫下硅对水稻幼苗生长与生理响应的影响

以水稻(Oryza sativa L.)"辽粳9"为试验对象,在消除阳离子影响的条件下,通过水培试验,研究镉胁迫下硅对水稻幼苗的生长与生理响应的影响。试验设置5个处理,除对照外,各处理初始镉离子(Cd~(2+))浓度均为1 mg·L~(-1),施硅量(以SiO_2计)依次为0、50、100、150 mg·L~(-1)。结果表明:镉胁迫下,水稻幼苗生长受到抑制,施硅显著地提高了水稻茎叶和根的干重;镉胁迫下,水稻幼苗过氧化物酶(POD)活性和丙二醛(MDA)含量受到诱导而处于较高水平,过氧化氢酶(CAT)活性受到抑制;随施硅量的增加,POD活性逐渐降低(P0.05),CAT活性逐渐增加(P0.05),MDA含量降低(P0.05);镉胁迫下,水稻细胞受到损伤出现质壁分离现象,叶绿体基粒、片层模糊并且排列紊乱,线粒体膜部分破裂解体、嵴模糊甚至消失;施硅使水稻叶片细胞结构趋于完整、有序,叶绿体内淀粉粒数目增多、嗜锇颗粒减少并变小、片层排列逐渐整齐,线粒体及其嵴的数目增多、双层膜结构逐渐恢复。综合来看,镉胁迫下施硅促进水稻幼苗生长,缓解逆境生理响应,改善细胞超微结构,增强其抗镉胁迫能力。本试验条件下,硅施加量为150 mg·L~(-1)时,水稻幼苗缓解镉胁迫效果最好。

Effects of silicon on growth and physiological responses of rice seedlings under cadmium stress

The effects of silicon(Si) on growth and physiological responses of rice(Oryza sativa L. "Liaojing 9") seedlings under Cd stress were studied using a hydroponics experiment in which the effects of attendant cations had been eliminated. Four treatments were conducted with the initial content of 1 mg·L^-1 Cd²⁺, except for the control group, and different contents of Si(0, 50, 100, 150 mg·L^-1 SiO₂). The results demonstrated that the growth of the rice seedlings was inhibited under Cd stress, and that Si significantly enhanced the dry weights of shoots and roots. Moreover, higher peroxidase(POD) activity and malondialdehyde(MDA) content were induced, whereas catalase(CAT) activity was inhibited under Cd stress. With the increase in Si content, the activity of POD gradually decreased(P<0.05), the activity of CAT gradually increased(P<0.05), and MDA content decreased(P<0.05). The ultrastructure of rice cells was damaged and plasmolysis occurred. We found blurred and disorderly arranged chloroplast particles and lamellae, broken mitochondrial membranes, and blurred ridge under Cd stress. Following Si application,(1) the cell structure of rice leaves was intact,(2) the number of starch granules in chloroplast increased,(3) the osmium granules decreased and became smaller,(4) the lamellae were gradually neat,(5) the number of mitochondria and ridges increased, and (6) the bilayer membrane structure gradually recovered. To sum up, exogenous Si application promoted the growth of rice seedlings under Cd stress. Moreover, it alleviated the stress physiology response, improved the cell ultrastructure, and enhanced the ability of rice seedlings to resist Cd toxicity. Under the experimental conditions, the best effect of cadmium stress alleviation in rice seedlings occurred when the amount of silicon applied was 150 mg·L^-1.