镉胁迫对甜瓜幼苗抗氧化酶活性和光合作用的影响

为了探讨甜瓜对镉污染的耐受机制，以2个甜瓜品种（‘哈密绿’和‘秀绿’）为试验材料，在人工气候箱内采用基质栽培方式，研究了不同浓度镉对甜瓜幼苗生长、抗氧化酶活性和光合作用的影响。结果表明，镉胁迫下，2个甜瓜品种幼苗生长量、净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和气孔限制值(Ls)均降低，且镉浓度越高，下降幅度越大，胞间CO₂浓度(Ci)随着镉浓度的增加而升高；‘哈密绿’幼苗生长和光合机构受镉胁迫的影响小于‘秀绿’。抗氧化酶活性和可溶性蛋白随着镉浓度的增加先升后降；甜瓜‘哈密绿’脯氨酸含量随着镉浓度的增加而升高，而‘秀绿’脯氨酸含量随着镉浓度的增加先升后降，但都高于对照且差异显著；MDA和O₂·^-产生速率随着镉浓度的增加而升高，且‘哈密绿’增加幅度明显小于‘秀绿’。研究结果说明，随着镉浓度的提高，镉对甜瓜幼苗的毒害作用增加，但是甜瓜幼苗对镉毒害的响应存在明显的基因型差异。

Effects of Cadmium Stress on Antioxidant Enzyme Activities and Photosynthesis in Melon Seedlings

The experiment was carried out on ‘Hamilv’ and ‘Xiulv’ in climate chambers and substrates to investigate the effects of cadmium stress on growth, antioxidant enzyme activities and photosynthesis of melon seedlings in order to explore the possible mechanisms of cadmium tolerance of melon. The results showed that, with the increasing cadmium concentration, melon-seedling growth, net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr) and stomatal limitation (Ls) decreased; meanwhile, intercellular carbon dioxide concentration (Ci) increased significantly. The plant growth and photosynthetic apparatus of ‘Hamilv’ were less affected than that of ‘Xiulv’. Antioxidant enzyme activities and soluble protein content first increased, then decreased with the increasing concentration of cadmium. Proline content of ‘Hamilv’ increased significantly, meanwhile, the proline content of ‘Xiulv’ increased first followed by a decrease. With the increasing cadmium concentration, MDA content and O₂·^- producing rate increased and ‘Hamilv’ were less affected than ‘Xiulv’. These findings suggested that there was significant genotypical difference in melon in response to cadmium toxicity.