'Jinyan No. 4'cucumber was used as experimental material. The growth of cucumber radicles treated with different concentrations of p-hydroxybenzoic acid (0, 2.5, 5, 7.5, 10, 12.5, 15, 17.5 and 20 mmol·L-1) was investigated firstly, and 10 mmol·L-1 p-hydroxybenzoic acid was chosen for the further experiment. To investigate if melatonin alleviate p-hydroxybenzoic acid stress on cucumber radical elongation, 0, 1, 10, 25, 50, 75 and 100 μmol·L-1 melatonin were used to pretreat cucumber seeds for 24 h before 10 mmol·L-1 p-hydroxybenzoic acid treatment. The results suggested that exogenous melatonin could alleviate the radicle growth inhibition induced by p-hydroxybenzoic acid, and 75 μmol·L-1 melatonin showed the best effect. The growth of cucumber radical was significantly inhibited with an increase in p-hydroxybenzoic acid concentration, which was accompanied with lower activity of amylase. The melatonin pretreatment could significantly increase the activities of amylase and antioxidant enzymes in cucumber seeds resulting in lower accumulation of O2-·, H2O2 and MDA. Exogenous melatonin effectively reduced the PHBA stress on cucumber germination, which might be due to its function in decreasing oxidative stress and promoting starch catabolism.
以‘津研四号’黄瓜为试材,分别用0、2.5、5、7.5、10、12.5、15、17.5、20 mmol·L-1浓度的对羟基苯甲酸(PHBA)溶液对黄瓜种子处理72 h,选出胁迫作用较明显的10 mmol·L-1浓度;再分别用0、1、10、25、50、75、100 μmol·L-1的褪黑素(MT)溶液对10 mmol·L-1 PHBA下的黄瓜种子预处理24 h,72 h后观察MT的缓解效果.结果表明: 缓解PHBA胁迫效果最明显的MT浓度为75 μmol·L-1.随着PHBA浓度的升高,黄瓜种子胚根伸长的抑制作用明显增加;用10、25、50、75、100 μmol·L-1的MT预处理PHBA胁迫下的黄瓜种子均能不同程度缓解PHBA胁迫对胚根的抑制作用,其中以75 μmol·L-1的MT缓解效果最好.用MT预处理黄瓜种子可显著提高PHBA胁迫下黄瓜种子中淀粉酶活性及胚根中超氧化物歧化酶、过氧化物酶、过氧化氢酶和抗坏血酸过氧化物酶活性,并降低胚根中O2-·的产生速率及H2O2和丙二醛含量.外源MT能够通过降低氧化胁迫和促进淀粉的分解转化来降低PHBA对黄瓜发芽的影响.
Keywords: alleviating effect; autotoxicity; cucumber; melatonin; p-hydroxybenzoic acid.