O3对水稻叶片氮代谢、脯氨酸和谷胱甘肽含量的影响

臭氧(O3)被认为是重要的气污染物之一,水稻又是主要的粮食作物,因而准确地评估O3浓度升高对水稻生长发育的影响具有十分重要的意义。采用开顶式气室法模拟研究了O3对水稻叶片可见伤害症状、氮代谢、脯氨酸和谷胱甘肽含量的影响。结果显示,O3污染胁迫会导致水稻叶片产生明显的伤害症状,具体表现为:老叶叶鞘褪绿,有褐斑,直至完全干枯;稻穗小且黄化,籽粒不饱满;水稻成熟期提前等。O3浓度升高对水稻叶片的硝酸还原酶活性有显著影响。当O3浓度为40、80和120nL.L-1时,水稻叶片硝酸还原酶活性与对照组相比均降低,其中,分蘖期分别降低了25.3%、67.4%和86.3%;拔节期分别降低了57.4%、75.7%和97.8%;抽穗期分别降低了91.0%、97.2%和99.3%;乳熟期分别降低了89.5%、89.5%和96.7%。水稻叶片铵态氮和硝态氮含量随着O3浓度的升高而显著地降低,例如当O3浓度为40、80和120nL.L-1时,与对照相比,水稻叶片硝态氮含量分别降低46.3%、52.7%和65.7%,铵态氮含量分别降低6.5%、12.9%和43.4%。O3污染胁迫下水稻叶片脯氨酸含量在不同生长期变化不同,分蘖期、拔节期和抽穗期脯氨酸含量在40nL.L-1浓度O3熏蒸下急剧地提高,但是随着O3浓度的增加,脯氨酸含量又不断地降低。在水稻乳熟期,脯氨酸含量均随着O3浓度的增加而显著地下降。O3污染胁迫导致水稻叶片还原型谷胱甘肽(GSH)含量显著低于对照组,而氧化型谷胱甘肽(GSSG)含量显著高于对照组。当O3浓度为40、80和120nL.L-1时,乳熟期水稻叶片GSH含量分别比对照组降低68.7%、80.2%和78.2%,GSSG含量分别比对照提高494.4%、527.2%和439.8%。研究表明,O3污染胁迫对水稻叶片氮代谢和抗氧化系统产生了极显著的影响。

Effects of Ozone on Nitrogen Metabolism, Proline and Glutathione of Rice Leaf

Ozone (O₃) is recognized as one of the most important air pollutants. It is of significance to accuratly evaluate the effect of elevated O₃ concentration on the growth and development of rice which is the main food crop. The ozone-induced visible injury symptom, and the effects of ozone on nitrogen metabolism, proline content and glutathione content in rice leaf were studied using open top chamber (OTC) method. Results showed that O₃ stress could significantly make damage to the rice leaf, such as chlorosis, brown spots, etiolation and withering in old leaf sheath, causing the grain to shrink and not full, causing rice maturity ahead of time. There were significant effects on the activities of nitrate reductase (NR) of the rice leaf under O₃ stress. When the O₃ concentrations were 40, 80 and 120 nL·L^-1, compared with the control group, the activities of NR in rice leaf decreased by 25.3%, 67.4% and 86.3% in the tillering stage, by 57.4%, 75.7% and 97.8% in the jointing stage, by 91.0%, 97.2% and 99.3% in the heading stage, and by 89.5%, 89.5% and 96.7% in the milk stage, rerpectively. The contents of NH⁴⁺-N and NO₃--N in rice leaf decreased significantly with increasing of the O₃ concentration. For example, when the O₃ concentrations were 40, 80 and 120 nL·L^-1, compared with the control group, the content of NO₃--N decreased by 46.3%, 52.7% and 65.7%, and the content of NH⁴⁺-N decreased by 6.5%, 12.9% and 43.4%. The effects of O₃ on proline contents in rice leaf varied in different stages. The contents of proline dramatically increased at the O₃ concentration of 40 nL·L^-1 but gradually decreased with further increasing O₃ concentrations in the tillering stage, the jointing stage and the heading stage. The contents of proline significantly decreased when the O₃ concentrations increased in the milk stage of rice. O₃ stress decreased GSH contents in the rice leaf while increased GSSG contents compared with the control group. At the O₃ concentrations of 40, 80 and 120 nL·L^-1, GSH contents in the rice leaf decreased by 68.7%, 80.2% and 78.2%, while GSSG contents increased by 494.4%, 527.2% and 439.8% compared with the control group in the rice milk stage. It can be concluded that O₃ stress had significant effects on nitrogen metabolism and anti-oxidant system of rice leaf.