摘要： 为了探究外源褪黑素对向日葵幼苗耐旱性的影响并明确其作用机制，以晋葵5号为试验材料，研究了叶面喷施50~200 μmol/L外源褪黑素对干旱胁迫下向日葵幼苗生长、光合及抗氧化系统的影响。结果表明，干旱胁迫显著抑制了向日葵幼苗的生长，随着干旱胁迫时间的延长，向日葵幼苗叶片叶绿素含量、净光合速率（Pn）、气孔导度（Gs）及蒸腾速率（Tr）均逐渐下降，相对电导率、MDA含量、H₂O₂含量及₂^·产生速率均逐渐上升，抗氧化酶（SOD、POD、CAT、APX、GR）活性及抗氧化剂（AsA和GSH）含量则先升高后降低。外源施用褪黑素可显著提升干旱胁迫下向日葵幼苗叶片的叶绿素含量、Pn、Gs及Tr，抗氧化酶（SOD、POD、CAT、APX、GR）活性和抗氧化剂（AsA和GSH）含量得到进一步提升，显著抑制了MDA、H₂O₂及₂^·在叶片中的积累，以浓度为100 μmol/L处理效果最佳；在干旱胁迫10 d时，100 μmol/L褪黑素处理的向日葵幼苗株高、茎粗、叶面积、干质量、叶绿素含量以及Pn、Gs、Tr及SOD、POD、CAT、APX、GR活性和AsA、GSH含量分别较CK2（干旱胁迫）提升7.13%，7.48%，8.13%，12.48%，61.43%，52.71%，60.00%，39.29%，43.03%，70.16%，57.00%，85.22%，148.09%，20.00%，40.98%；相对电导率、MDA含量、H₂O₂含量、₂^·产生速率分别较CK2降低26.79%，35.81%，24.33%，23.13%。结果说明，外源褪黑素通过提高干旱胁迫下向日葵幼苗叶片的光合作用和活性氧清除能力，从而缓解干旱胁迫造成的伤害，提高耐旱性，以100 μmol/L处理效果最佳。

关键词: 向日葵幼苗, 褪黑素, 干旱胁迫, 光合作用, 抗氧化系统

Abstract: In the paper, an oil sunflower cultivar(Jinkui 5)was selected as the experimental material to study the effects of 50-200 μmol/L exogenous melatonin treatment on plant growth, photosynthesis and antioxidant system of sunflower seedling under drought stress. The results showed that the growth of sunflower seedlings were significantly inhibited under drought stress. With the extension of drought stress time, the chlorophyll content, Pn, Gs and Tr gradually decreased, and the relative conductivity, MDA content, H₂O₂ content and O₂^· production rate increased, while the activities of antioxidant enzymes(SOD, POD, CAT, APX and GR)and the content of antioxidants(AsA and GsH)increased first and then decreased. Exogenous melatonin significantly reduced MDA content, O₂^· production rate and H₂O₂ content, and raised the chlorophyll content, the Pn, Gs and Tr value, the activities of antioxidant enzymes(SOD, POD, CAT, APX and GR)and the AsA and GsH contents in sunflower seedling leaves under drought stress. The best effect of MT concentration was 100 μmol/L.At 10 d of drought stress, the plant height, stem diameter, leaf area, dry weight, chlorophyll content, Pn, Gs, Tr, SOD, POD, CAT, APX and GR activities, AsA and GSH contents of sunflower seedlings treated with 100 μmol/L MT increased by 7.13%,7.48%,8.13%,12.48%,61.43%,52.71%,60.00%,39.29%,43.03%,70.16%,57.00%,85.22%,148.09%,20.00% and 40.98%, respectively, compared with CK2(drought stress), and the relative conductivity, MDA content, H₂O₂ content and O₂^· production rate decreased by 26.79%,35.81%, 24.33% and 23.13%, respectively. These results suggested that exogenous melatonin could effectively alleviate the damage of drought stress and improve the resistance of sunflower seedling to drought stress by improving the photosynthesis and active oxygen scavenging capacity of sunflower seedling, and the best effect of MT concentration is 100 μmol/L.

Key words: Sunflower seedling, Melatonin, Drought stress, Photosynthesis, Antioxidant system

中图分类号: 

• S565.5