为探究外源硫S对玉米响应镉（Cd）胁迫的影响机制，采用水培试验，研究了根部施加外源SO42-对Cd胁迫下玉米幼苗相关关键生理指标的影响，并分析了Cd在玉米组织和亚细胞分布情况。结果表明，外源SO42-处理，可显著降低Cd胁迫下玉米叶片与根中的丙二醛含量、相对电导率和抗氧化酶（SOD、CAT）活性。同时，根中抗坏血酸、非蛋白硫醇、植物螯合素含量在外源SO42-处理后显著上升，而在叶片中的变化不显著。外源SO42-处理可降低玉米叶片中Cd含量，而提升在根中的含量。进一步分析表明，根细胞壁和液泡中的Cd含量显著上升，从而减少Cd向地上部分的运输量。另外，根细胞液泡膜中Cd运输专一性基因HMA3在外源SO42-处理后，表达水平显著增强。因此，外源S可以通过提升Cd胁迫处理下玉米根细胞壁中Cd含量和抗坏血酸的保护作用，同时促进液泡的区室化作用，降低Cd向玉米地上部位的转运，以增强玉米对Cd胁迫的耐受性
英文摘要:
To investigate the physiological mechanism of surplus sulfur on alleviating cadmium stress in Zea Mays, a hydroponic experiment was applied at the present study, and the change of some critical parameters in leaves were analyzed. The Cd distribution in different organs and subcellular components were determined as well. Our results showed that (NH4)2SO4 (surplus sulfur donor) treatment could significantly mitigate both the Cd (CdCl2?2.5H2O)-induced increase of MDA content in the root and relative electrolyte leakage in the root and leaf. SO42- lead to a reduced effect on the Cd-induced increase in the activities of some typical antioxidant enzymes, including superoxide dismutase (SOD) and catalase (CAT). The changes on the contents of ascorbic acid, non-protein thiol and phytochelatins in the root could also be increased by SO42- relative to Cd treatment. Further analysis revealed that the Cd content in root cell wall and vacuole were increased. Therefore, the decreased transmit of Cd from root to the leaves were observed. Furthermore, the expression of HMA3 gene was enhanced by SO42- treatment under Cd condition. Concludingly, SO42- counteracts Cd toxicity strongly in Zea Mays via regulating antioxidant metabolism and enhancing Cd accumulation in the cell wall and vacuole of the root.
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