摘要:
镉(Cd)是非必需和毒性最强的重金属元素之一,不合理的开发利用可导致土壤受到Cd的严重污染,严重危及土壤环境或水环境。以苎麻为材料,采用模拟镉(Cd)污染盆栽培养法,选择21 d和49 d等2个不同胁迫期,测定不同浓度Cd2+胁迫下苎麻根系与叶片中渗透调节物质含量、超氧化物岐化酶(SOD)活性、过氧化物酶(POD)活性、过氧化氢酶(CAT)活性、丙二醛(MDA)含量及根系活力的变化。结果表明,高浓度胁迫49 d后,苎麻根系中的渗透调节物质含量明显高于叶片含量,且极显著高于对照,并在240 mg·L-1 Cd处理下出现最高值;胁迫49 d时,根系与叶片的渗透调节物质含量与Cd2+浓度极显著正相关。在2个不同胁迫周期,苎麻根系的SOD与POD活性均明显高于叶片;在胁迫21 d时,根系的CAT活性低于叶片,而胁迫49 d后,则明显高于叶片;胁迫21 d时,苎麻根系与叶片的抗氧化酶活性均较胁迫49 d要高;胁迫49 d时,根系POD活性与Cd2+浓度呈极显著正相关,表明根系POD酶在抗氧化酶中占主导地位。不同胁迫时长下苎麻根系或叶片的MDA含量变化趋势不明显,但根系或叶片受胁迫21 d后的MDA含量随Cd2+浓度增加的波动相对受胁迫49 d后的更明显,表明植物早期生理功能出现暂时性的修复。2个不同胁迫周期内,不同浓度镉胁迫下苎麻的根系活力均比对照组下降。研究显示,苎麻根系与叶片对镉胁迫的应答机制不同,且在不同胁迫时间下的响应机理差异较大,根系表现出更强的耐受能力。
关键词:
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镉胁迫
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苎麻
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叶
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抗氧化酶
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根系活力
Abstract:
Cadmium (Cd) is one of the most toxic heavy metal elements and the non-essential，unreasonable exploitation and utilization may lead to the serious pollution of soil by Cd, which endanger the soil environment or water environment. Our objective was to reveal the differences in the contents of osmoregulation substances, superoxide dismutase (SOD) activities, peroxidase (POD) activities, catalase (CAT) activities, malondialdehyde (MDA) contents in roots and leaves and root activities in ramie (Boehmeria nivea) under different cadmium stress in different stress duration. Under long stress duration of 49 days, the content of osmoregulation substances in roots was significantly higher than those in leaves at high cadmium concentration, simultaneously being significantly higher than those of the control group without any heavy metal stress. The concentration of each osmoregulation substance in roots peaked at the cadmium stress of 240 mg·L-1. The contents of osmoregulation substance in roots and leaves were both positively correlated to cadmium concentrations under the stress duration of 49 days. The SOD and POD activities in roots were both significantly higher than those in leaves under the two different stress duration (21 d and 49 d). Furthermore, the contents of CAT activities in roots were lower than those in leaves under the stress duration of 21 days, but were higher than those in leaves under the stress duration of 49 days. The antioxidant enzyme activities in roots and leaves under the stress duration of 21 days were higher than those with duration of 49 days. We also found that the POD activity in roots at the stress duration of 49 days were positively correlated to cadmium concentrations, indicating that the POD activity in roots dominated in antioxidant enzymes. The changes of MDA contents in roots or leaves were not significant under the stress of two different duration, but the fluctuation of the MDA content in roots or leaves under the stress duration of 21 days showed more obvious than those of 49 days with increasing cadmium concentrations, suggesting that plant physiological function exhibited a temporary repair in the early stress period. Compared to the control group, the root activities decreased both under different cadmium stress and different stress durations. We concluded that the mechanism of physiological response to cadmium in roots and leaves under different stress durations is very different, but the roots show stronger resistance to stress.
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