外源褪黑素对盐胁迫下紫花苜蓿幼苗抗氧化能力以及光合作用效率的影响
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Effect of Exogenous Melatonin on Antioxidant Capacity and Photosynthetic Efficiency of Alfalfa Seedling under Salt Stress
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    摘要:

    紫花苜蓿为多年生豆科优良牧草,土壤盐碱化是其产量的重要限制因素。该研究以‘中苜1号’紫花苜蓿为材料,在盐胁迫浓度和褪黑素浓度筛选试验基础上,设置盐(150 mmol/L NaCl)和褪黑素(30、50、80 μmol/L)单独及复合处理,采用水培根灌褪黑素的方法,探究外源褪黑素对盐胁迫下紫花苜蓿幼苗生长特性、膜透性、渗透调节、抗氧化物酶以及光合作用指标的影响。结果表明:(1)紫花苜蓿幼苗生长受到盐胁迫的显著抑制,而在单独褪黑素处理下无显著变化;各浓度褪黑素处理均可有效缓解盐胁迫对紫花苜蓿生长造成的伤害,并以150 mmol/L NaCl+80 μmol/L褪黑素处理(NaCl+MT2)效果最佳,其幼苗根长、根鲜重和根干重分别比盐胁迫处理显著增加了34.52%、41.93%和19.61%。(2)盐胁迫显著增加了紫花苜蓿幼苗细胞膜系统的透性和膜脂过氧化程度, NaCl+MT2处理幼苗叶片的相对电导率和MDA含量分别比盐胁迫处理显著降低了27.18%和30.24%,同时使幼苗叶片的相对含水量显著提高,脯氨酸含量却显著降低,表明外源褪黑素有效缓解了盐胁迫下细胞失水危害和细胞膜损伤的程度。(3)NaCl+MT2处理幼苗叶片的POD和SOD活性分别比盐胁迫处理显著提高31.45%和41.41%,其CAT活性却无显著变化,表明外源褪黑素可显著增强紫花苜蓿幼苗叶片POD、SOD活性,提高其活性氧的清除能力,减轻盐胁迫诱导的过氧化伤害。(4)盐胁迫显著抑制了紫花苜蓿幼苗光合作用效率,而 NaCl+MT2处理幼苗叶片的净光合速率、气孔导度和蒸腾速率较盐胁迫处理分别显著增加了30.27%、45.1%、42.15%。研究发现,盐胁迫致使紫花苜蓿幼苗叶片的活性氧积累显著增加,抗氧化物酶活性显著降低,显著降低了其光合作用效率,外源褪黑素通过提高紫花苜蓿的抗氧化能力和光合作用效率来促进幼苗生长,从而增强了紫花苜蓿的耐盐性。

    Abstract:

    Alfalfa, the perennial legume forage, soil salinization is becoming a yield limiting factor of it. ‘Zhongmu No.1’, as one of the Alfalfa, was used as the material in this study. Based on the screening test of salt stress and melatonin, salt (150 mmol/L NaCl) and melatonin (30, 50, 80 μmol/L MT) separate and combination treatment were selected. The effects of exogenous melatonin on the growth characteristics, membrane permeability, osmotic regulation and effects of antioxidants enzymes and photosynthetic indexes were shown in this article. The results showed that: (1) the growth of alfalfa seedlings was significantly inhibited by salt stress, but not affected by various concentrations of melatonin. All melatonin treatments effectively alleviated the damage caused by salt stress to the growth of alfalfa, and the effect of 150 mmol/L NaCl+ 80 μmol/L melatonin treatment (NaCl + MT2) was the best, the seedling foot length, the root fresh weight and root dry weight increased significantly by 34.52%, 41.93% and 19.61% compared with salt stress treatment, respectively. (2) Salt stress significantly increased the permeability of cell membrane system and the degree of membrane lipid peroxidation of alfalfa seedlings. The relative conductivity and MDA content of seedling leaves treated with NaCl + MT2 were significantly lower than those treated with salt stress by 27.18% and 30.24%, respectively. At the same time, the relative water content in seedling leaves was significantly increased, but the proline content was significantly reduced, exogenous melatonin effectively alleviated the damage of cell water loss and cell membrane under salt stress. (3) The activities of POD and SOD in the leaves of NaCl + MT2 seedlings were significantly higher than those of salt stress treatment by 31.45% and 41.41%, respectively. However, the CAT activities had no significant change. Exogenous melatonin could significantly enhance the activities of POD and SOD in the leaves of alfalfa seedlings, improve the scavenging ability of reactive oxygen species and reduce the peroxidation damage induced by salt stress. (4) Salt stress significantly inhibited the photosynthetic efficiency of alfalfa seedlings, while the net photosynthetic rate, stomatal conductance and transpiration rate of seedlings treated with NaCl + MT2 increased by 30.27%, 45.1% and 42.15%, respectively compared with salt stress. It was found that salt stress significantly increased the accumulation of reactive oxygen species in alfalfa seedling leaves, reduced the activities of antioxidant enzymes, and reduce its photosynthetic efficiency. Exogenous melatonin promoted the growth of alfalfa seedlings by improving its antioxidant capacity and photosynthetic efficiency, so our study provides a theoretical basis for improving alfalfa salt tolerance and reforming saline alkali land.

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赵丽娟,麻冬梅,王文静,等.外源褪黑素对盐胁迫下紫花苜蓿幼苗抗氧化能力以及光合作用效率的影响[J].西北植物学报,2021,41(8):1355-1363

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  • 在线发布日期: 2021-09-10
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