Cucumber (Cucumis sativus L. 'Xinchun 4') was used to explore the relationship between nitric oxide (NO) and calcium (Ca2+) during adventitious rooting under drought stress. Rooting parameters, endogenous Ca2+ fluorescent intensity and the antioxidant enzymes activity (SOD, CAT and APX) in cucumber explants under drought stress were investigated. The results showed that treatment with 200 μmol·L-1 CaCl2 and 0.05% PEG significantly improved the number and length of adventitious root in cucumber explants under drought stress, while the application of Ca2+ chelating agent (EGTA) and channel inhibitor (BAPTA/AM) significantly decreased NO-induced number and length of adventitious root under drought stress. Under drought stress, the fluorescence intensity of Ca2+ in hypocotyls treated with NO and CaCl2 was improved, however, the Ca2+ fluorescence intensity in the hypocotyls treated with NO scavenger (cPTIO) was significantly lower than that in the hypocotyls treated with NO. Under drought stress, the activities of antioxidant enzymes in the cucumber explants were significantly promoted by the treatments with NO and CaCl2, however, Ca2+ chelating agent and channel inhibitor significantly decreased the activity of antioxidant enzymes induced by NO. In conclusion, Ca2+ might be involved in the process of NO-adjusted antioxidant enzymes activity during adventitious rooting under drought stress, which alleviated the negative effects of drought on the adventitious rooting and promoted the formation of adventitious roots.
以黄瓜品种‘新春4号'为材料,研究干旱胁迫下一氧化氮(NO)和钙离子(Ca2+)处理下黄瓜的生根指标、内源Ca2+荧光强度以及抗氧化酶(超氧化物歧化酶SOD、过氧化氢酶CAT、抗坏血酸过氧化物酶APX)活性,分析干旱条件下黄瓜不定根发生过程中NO和Ca2+之间的关系.结果表明: 200 μmol·L-1 氯化钙(CaCl2)和0.05%聚乙二醇(PEG)共处理显著提高了干旱条件下黄瓜不定根的根长和根数;添加Ca2+螯合剂(EGTA)和通道抑制剂(BAPTA/AM)处理显著降低了干旱条件下NO诱导的不定根根数和根长.干旱条件下,NO和CaCl2处理提高了黄瓜下胚轴内源Ca2+荧光强度;而NO清除剂(cPTIO)处理的Ca2+荧光强度显著低于NO处理.干旱条件下,NO和CaCl2处理显著提高了黄瓜下胚轴抗氧化酶活性;而Ca2+抑制剂或螯合剂处理显著降低了NO诱导的抗氧化酶活性.由此可见,干旱条件下Ca2+参与了NO调控黄瓜抗氧化酶活性,缓解了干旱胁迫对不定根形成产生的伤害,进而促进了不定根的发生.
Keywords: adventitious root; antioxidant enzymes; calcium ion; cucumbers; drought; nitric oxide.