UV-B辐射增强和O3浓度升高对大豆叶片内源激素和抗氧化能力的影响

揭示大豆叶片内源激素对UV-B和臭氧胁迫的代谢机制和响应方式,为从分子水平研究植物内源激素对UV-B(Ultraviolet-B)和O3(Ozone)胁迫的适应机制奠定基础。以大豆(Glycine max.)为试验材料,利用开顶式气室研究UV-B(0.32W/m2)和O3((110±10)nmol/mol)复合胁迫对大豆叶片内源激素含量及活性氧代谢系统的影响。结果表明:在大豆整个生育期内,与对照相比,UV-B胁迫使大豆叶片ABA(Abscisic acid)含量、ZR(Zeatin riboside)含量和IAA(Indoleacetic acid)含量显著降低,IAA/ABA、ZR/ABA、(IAA+ZR)/ABA比值升高,O·-2(Superoxide anion free radical,O·-2)产生速率和MDA(Malonaldehyde)含量升高,SOD(Superoxide dismutase)、CAT(Catalase)和POD(Peroxidase)活性显著降低;高浓度O3胁迫下,大豆叶片ABA和IAA含量显著下降、ZR含量显著增加,IAA/ABA、ZR/ABA、(IAA+ZR)/ABA值显著升高,O·-2产生速率和MDA含量增加,SOD、CAT和POD活性显著降低;UV-B和O3复合胁迫下,大豆叶片ABA含量、ZR含量和IAA含量降低,ZR/ABA、(IAA+ZR)/ABA值下降,而IAA/ABA值升高,O·-2产生速率和MDA含量显著增加,SOD、CAT和POD活性显著降低。UV-B辐射增强和O3浓度升高单一及复合作用使大豆叶片内源激素间平衡改变,进而影响大豆叶片的代谢水平。持续胁迫下,植株抗氧化能力下降,对大豆表现为伤害效应。UV-B和O3复合胁迫比单独胁迫时的影响有所加深,但是小于两者单独作用时影响的简单累加。

Effects of plant endogenous hormones and antioxidant ability in soybean leaves under UV-B and ozone stress

Widespread areas of crop production are presently at risk for damage from ambient atmospheric ozone (O₃) concentrations and ultraviolet-B radiation (UV-B). The concentration of tropospheric ozone and UV-B have been rising due to aggravating urbanization since the Industrial Revolution, which has had a significant impact on plants and plants play an important role in adjusting structure and function of the ecosystem. Thus, to correctly evaluate how elevated O₃ concentration and UV-B radiation affect plants is of great significance. The effects of O₃ and UV-B on plant growth and some physiological indexes such as photosynthesis have been reported separately for a number of species by controlled experiments,but only few experiments have focused on their interaction. It is not distinct on interaction mechanism between O₃ and UV-B. Especially, it is lack of reports to investigate the effects on endogenous hormone of a single species exposed to UV-B and O₃ under well-controlled experimental conditions.Open-top chambers were utilized to investigate endogenous hormones content, change of lipid peroxidation extent, ROS (Reactive oxygen species, ROS) production rate, anti-oxidation enzymes activities in soybean leaves under elevated ozone concentration (110±10 nmol/mol) and UV-B radiation (0.32 W/m²) singly and in combination treatment. The results indicated that enhanced UV-B radiation induced a decrease on abscisic acid (ABA) content, indoleacetic acid (IAA) content, zeatin riboside (ZR) content, the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and a increase on ratio of IAA/ABA, ZR/ABA, (IAA+ZR)/ABA, superoxide anion free radical (O₂·) production rate, Malondialdehyde (MDA) content, in soybean leaves during the whole growth stage and the ratio of IAA/ABA, ZR/ABA, (IAA+ZR)/ABA showed significantly increase at flowering stage,but slightly decrease at podding stage. Elevated O₃ concentration exposure showed the similar effects, which resulted in lower ABA content, IAA content, the activities of SOD, CAT, POD and higher ZR content, O₂· production rate, MDA content, ratio of IAA/ABA, ZR/ABA, (IAA+ZR)/ABA compared with the control and the ratio of IAA/ABA, ZR/ABA, (IAA+ZR)/ABA showed significantly increase at branching stage and flowering stage. A increase of ZR content may improve the antioxidant ability of soybean. UV-B radiation and O₃ concentration combined stress induced a decrease on ABA content, IAA content, ZR content, the activities of SOD, CAT, POD, ratio of ZR/ABA, (IAA+ZR)/ABA and a increase on IAA/ABA ratio, O₂· production rate, MDA content. The ratio of ZR/ABA showed significantly decrease at flowering stage and podding stage, but the difference of the ratio of IAA/ABA and (IAA+ZR)/ABA is not significant at the whole growth stage. The antagonism effect appears between ABA and ZR under enhanced UV-B and O₃ in combination. Obviously, enhanced UV-B radiation and elevated O₃ concentration caused significant variation on endogenous hormone balance and accelerated ROS metabolism rates and reduced anti-oxidative enzymes activities in soybean leaves. Compared with UV-B and O₃ singly, UV-B and O₃ in combination caused significant decrease in soybean endogenous hormone content and antioxidant ability. UV-B and O₃ in combination enhanced the negative effect on soybean compared with UV-B and O₃ alone but less than the simple accumulation effects of UV-B and O₃ alone.