模拟酸雨条件下Pb^(2+)和Cr^(6+)对蕹菜光合作用及品质的影响

Impacts of Pb^(2+) and Cr^(6+) on the photosynthesis and quality of Ipomoea aquatica Forsk under simulated acid rain

以蕹菜(Ipomoea aquatica Forsk.)为供试对象,通过盆栽试验,研究了不同酸度模拟酸雨(AR)条件下,Pb2+和Cr6+对其光合作用、营养品质及食用安全性的影响。结果表明:酸雨条件下,重金属对蕹菜叶片光合作用和品质的胁迫表现为Pb>Pb+Cr>Cr;随酸度增加,AR+Pb和AR+Pb+Cr处理的危害性显著增加,pH=3.5时,AR+Pb+Cr处理的胁迫性明显大于其他处理水平,对蔬菜造成伤害;3个光合作用参数均随酸雨酸度增加有不同程度的下降,但对胁迫的敏感性存在差异;pH<5.6时,蕹菜中蛋白质和游离氨基酸含量与pH值呈正相关;随酸度增加,可溶性糖含量增加,而还原性糖含量下降,表现出对环境胁迫的应激反应;除了Cr污染处理外,Pb污染和Pb+Cr污染都能显著促进蕹菜中硝态氮积累,其含量随酸雨酸度上升而增加;蕹菜中Pb和Cr存在竞争吸附作用,且随着酸雨酸度下降,蕹菜对2种重金属的富集有加快趋势。

A pot experiment was conducted to study the impacts of Pb^2＋ and Cr^6＋ on the photosynthesis, nutritional quality, and food safety of water spinach （lpomoea aquatica Forsk. ） under simulated acid rain （AR） with different acidity. The results showed that under AR, the stress of test heavy metals on the photosynthesis and quality of the spinach decreased in the order Pb 〉 Pb ＋ Cr 〉 Cr. With increasing acidity of AR, the impact of treatments AR ＋ Pb and AR ＋ Pb ＋ Cr increased remarkably, and the stress effect of treatment AR ＋ Pb ＋ Cr was greater than that of the other treatments under pH = 3.5. Compared with the control, three parameters of photosynthesis decreased with increasing acidity of AR, but had different susceptivity to the stress. The protein and free amino acid contents in the spinach had positive correlations with pH when the pH was 〈 5.6, and, with increasing acidity, the soluble sugar content increased while reductive sugar content decreased, being a kind of response to the environmental stress. Treatments Pb and Pb ＋ Cr notably promoted the nitrate nitrogen accumulation, and the nitrate nitrogen content in the spin- ach increased with the acidity of AR. There existed a competition between the adsorption of Pb and Cr in the spinach, and the enrichment of the two heavy metals would be sped up with decreasing acidity of AR.