摘要：

为探究褪黑素对盐胁迫下小豆幼苗生长发育的影响,以保红876为材料,设置4个处理:CK(清水)、S(60 mmol/L NaCl)、MT(50 μmol/L 褪黑素)和S-MT(60 mmol/L NaCl和50 μmol/L 褪黑素),并分析了小豆幼苗生长指标、光合指标、矿质元素离子含量和抗氧化酶活性的变化。结果表明,在盐胁迫条件下,较CK处理,小豆幼苗的生长受到明显抑制,叶绿素含量、净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)和胞间CO₂浓度(Ci)显著降低;叶、茎中Na⁺含量显著上升,叶片中Ca²⁺含量显著上升而Mg²⁺含量则显著下降,豆苗Na⁺/K⁺比值显著增加;MDA和H₂O₂含量显著上升,破坏了膜脂选择透性。盐胁迫下施加褪黑素后,较S处理,显著提高了豆苗株高、叶面积和生物量,总根长显著增加;同时提高了叶绿素含量、叶片Pn、Tr和Ci;叶、茎中Na⁺和K⁺含量显著降低,叶片Mg²⁺含量显著升高同时Ca²⁺含量显著降低,豆苗Na⁺/K⁺比值降低;MDA、 {\mathrm{O}}_2^{-}和H₂O₂含量下降;提高了叶片和根系SOD、POD和CAT活性。正常条件下,施加褪黑素可以促进豆苗的生长,提高幼苗的光合能力,提高了可溶性蛋白含量。对15个代表指标进行Spearman相关分析,发现总根长、叶绿素含量、净光合速率、抗氧化酶活性均与Na⁺/K⁺比值和ROS含量呈显著或极显著负相关。综上所述,盐胁迫下,褪黑素通过激活了豆苗抗氧化酶活性,可直接和间接的减少H₂O₂含量,保持膜脂渗透稳定性,从而利于植物体内Na⁺/K⁺平衡;同时,H₂O₂和Ca²⁺作为信号分子,在褪黑素调节细胞内离子平衡的过程中存在协同效应,从而提高植物的耐盐能力。

关键词: 小豆, 褪黑素, 盐胁迫, Na⁺/K⁺平衡

Abstract:

In order to explore the effects of melatonin on the growth and development of adzuki bean seedlings under salt stress,a phytotron experiment was conducted with Baohong 876 as the material and four treatments:CK(Clear water),S(60 mmol/L NaCl),MT(50 μmol/L melatonin)and S-MT(60 mmol/L NaCl and 50 μmol/L melatonin).The growth indexes,photosynthetic indexes,mineral ion contents and antioxidant enzyme activities of adzuki seedlings were analyzed using classical physicochemical determination.The results showed as follows:under salt stress,compared with CK treatment,the growth of adzuki bean seedlings was significantly inhibited,chlorophyll content,net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductivity(Gs)and intercellular CO₂ concentration(Ci)were significantly decreased;the contents of Na⁺ in leaves,stems were significantly increased.Meantime,the content of Ca²⁺ in leaves was significantly increased while the content of Mg²⁺ was significantly decreased,and the ratio of Na⁺/K⁺ was significantly increased.The contents of MDA and H₂O₂ increased significantly,which damaged the selective permeability of membrane lipid.Compared with S treatment,the plant height,leaf area,biomass,and total root length of adzuki bean seedlings were significantly increased under S-MT condition.Meantime,chlorophyll content,leaf Pn,Tr,and Ci were increased.The contents of Na⁺ and K⁺ in leaves,stems were significantly decreased,the content of Mg²⁺ in leaves was significantly increased and Ca²⁺ was significantly decreased,and the Na⁺/K⁺ ratio was decreased.The contents of MDA, {\mathrm{O}}_2^{-} and H₂O₂ decreased.The levels of SOD,POD and CAT activity in leaves and roots were increased.Under normal conditions,the application of melatonin could promote the growth of adzuki bean seedlings,improve the photosynthetic capacity of seedlings,and increase the content of soluble protein.Spearman correlation analysis was performed on 15 representative indicators,and it was found that total root length,chlorophyll content,net photosynthetic rate,and antioxidant enzyme activities were significantly or extremely significantly negatively correlated with Na⁺/K⁺ ratio and ROS.In summary,under salt stress,melatonin can directly and indirectly reduce H₂O₂ content and maintain the stability of membrane lipid permeability by activating the antioxidant enzyme activity of adzuki bean seedlings,thus maintaining the Na⁺/K⁺ balance in plants.Meanwhile,H₂O₂ and Ca²⁺,as signaling molecules,have a synergistic effect in the regulation process of melatonin regulating intracellular ion balance,thereby improving the salt tolerance of plants.

Key words: Adzuki bean, Melatonin, Salt stress, Na⁺/K⁺ equilibrium