大气汞浓度升高对水稻叶片生理效应的影响研究

采用大田开顶式气室熏气实验,研究大气汞浓度升高对水稻叶片气体交换参数、脯氨酸、丙二醛的积累以及超氧化物歧化酶活性的影响。实验结果显示,水稻叶片净光合速率(Pn)和气孔导度(Gs)随大气汞浓度的升高均较对照略微下降,表明大气汞浓度的升高对水稻光合作用和气孔开放程度有一定影响;扬花期水稻胞间CO2浓度(Ci)随大气汞浓度的升高明显降低(P0.05)表明Pn的略微下降属于气孔限制,同时蒸腾速率(Tr)显著增加(P0.01)表明大气汞对水稻的蒸腾生理功能有一定的影响。乳熟期水稻叶片气体交换参数与大气汞浓度无显著差异(P0.05),且各指标均低于扬花期。水稻叶片脯氨酸(Pro)含量在拔节期随大气汞浓度的升高而显著增加(P0.05),扬花期先升高后下降,在45 ng·m-3时达到最大,成熟期无显著差异(P0.05);水稻叶片丙二醛(MDA)含量在拔节期先升高后下降,45 ng·m-3时达到最大,扬花期和成熟期均无显著差异(P0.05);水稻叶片超氧化物歧化酶(SOD)活性在拔节期先升高后下降,15 ng·m-3时达到最大,扬花期无显著差异(P0.05)。以上结果表明大气汞浓度的升高可以引起水稻叶片膜脂过氧化以及脯氨酸和丙二醛含量的积累,且随着体内Pro、MDA和SOD对大气汞胁迫的协同反应,水稻对逆境的适应能力增强,对汞胁迫产生了耐受性。

Physiological Responses of Rice Leaves to the Elevated Gaseous Elemental Mercury in the Atmosphere

The effects of elevated gaseous elemental mercury (GEM) on gas exchange parameters, accumulation of proline (Pro) and malondialdehyde (MDA), activity of superoxide dismutase (SOD) in rice foliage were studied with field open-top chambers (OTCs) fumigation experiment. The results showed that the net photosynthesis rate (Pn) and stomatal conductance (Gs) were less slightly in GEM treatment than those in the control, which indicating that elevated GEM had some effect on photosynthesis and stomatal openness of rice leaves. In flowering stage of rice, the distinct decrease(P<0.05) of intercellular CO2 concentration (Ci) with elevated GEM indicated that stomatal limitation led to the slight decrease of Pn, and the significant increase (P<0.01)of transpiration rate (Tr)with elevated GEM showed that the physiological function of rice transpiration was effected by Hg in the atmosphere. Gas exchange parameters of rice leaves in milky stage were insignificantly difference with GEM in air (P>0.05) and lower than that in flowering stage. Proline concentrations in rice foliage were increased obviously with elevated GEM (P<0.05) in jointing stage, declined after increasing and reached to the maximum value at 45 ng·m-3 in flowering stage, and it was no significant difference (P>0.05) in mature stage among four treatments. The contents of MDA in rice foliage increased first and reached the highest value at 45 ng·m-3, and then decreased in jointing stage, and it was no significant difference (P>0.05) with the increase of GEM in flowering and mature stage. The activity of SOD in rice foliage also increased first and then declined at 15 ng·m-3 in jointing stage, and there was no significant difference (P>0.05) in flowering stage. These results suggested that elevated GEM in air can cause membrane lipid peroxidation and accumulation of Pro and MDA in rice foliage, furthermore the ability of adapting to adversity and the tolerance to elevated GEM for rice were enhanced with the concerted reactions in vivo among Pro, MDA and SOD on the atmospheric mercury stress.