外源褪黑素对低温胁迫下大豆V1期幼苗光合荧光及抗氧化系统的影响

为缓解东北春大豆产区大豆苗期低温冷害，通过研究外源褪黑素（melatonin，MT）处理对低温胁迫下大 豆耐冷性的影响，明确MT提高大豆耐冷能力的作用途径及适宜浓度。以绥农26为供验试材，设置盆栽培养，在大 豆V1期（一节期）叶面喷施不同浓度MT（0、50、100、200 μmol·L-1），3 d后进行4℃低温处理，5 d后取样分析低温胁迫 下喷施不同浓度MT对V1时期大豆光合特性、活性氧代谢、渗透调节物质的影响。结果表明，较低温胁迫不喷施MT 相比，喷施MT处理能增强低温胁迫下叶片光合作用，Pn、Gs、Tr及光合色素含量均显著提高，且随着外源MT浓度增 加呈先上升后下降趋势，Chl a/b显著下降；保护酶SOD（超氧化物歧化酶）、POD（过氧化物酶）、CAT（过氧化氢酶）、 APX（抗坏血酸过氧化物酶）活性、Pro（脯氨酸）含量及植株根冠比显著上升，且在100 μmol·L-1浓度处理时作用效 果最明显；MDA（丙二醛）含量、叶片相对电导率显著下降。综上可知，在低温迫下施加外源褪黑素可以提高大豆V1 期光合速率、增加抗氧化酶活性，减轻膜脂过氧化反应并调节渗透物质含量，从而有助于缓解胁迫伤害，提高大豆 幼苗耐冷能力。

Effects of exogenous melatonin on photosynthetic fluorescence and antioxidant system of soybean V1 seedlings under low temperature

In order to alleviate chilling injury of soybean seedling in northeast spring soybean production area, effect of exogenous melatonin (MT) on chilling tolerance of soybean under low temperature stress was studied. The object was to find out appropriate MT concentration to improve chilling tolerance of soybean. Cultivar Suinong 26 was used and planted in pots. At V1 stage (one leaf stage of soybean), leaves were sprayed with different concentra⁃ tions of MT (0, 50, 100, 200 μmol·L-1) for 3 days, then moved to artificialclimate box for 5 days under low tempera⁃ ture (4℃). The effects of MT on photosynthetic characteristics, active oxygen metabolism and osmoregulation of soy⁃ beans under 4℃ showed that different concentrations of MT enhanced the photosynthesis. Pn, Gs, Tr and photosyn⁃ thetic pigment increased significantly. Chl a/b decreased significantly with the MT concentrations. The activity of SOD (superoxide dismutase), POD (peroxidase), CAT (catalase), APX (ascorbate peroxidase), Pro (proline) content and root-shoot ratio in leaves exposed to MT increased significantly, reaching a significant difference at concentra⁃ tion of 100 μmol·L-1. While MDA (malondialdehyde) content and the relative conductivity of leaves decreased sig⁃ nificantly. The results indicated that exogenous melatonin could alleviate stress injury and improve cold tolerance ofsoybean seedlings at V1 stage by increasing photosynthetic rate, antioxidant enzyme activity, and reducing mem⁃ brane lipid peroxidation and regulating osmotic substances.