外源5-ALA对干旱胁迫下玉米幼苗生长的缓解效应及抗氧化酶基因表达的影响

以抗旱玉米自交系郑58和干旱敏感自交系TS141为材料，研究了5-氨基乙酰丙酸（5-ALA）对15% PEG-6000模拟干旱胁迫下玉米幼苗生长的缓解效应及抗氧化酶基因表达的影响。结果表明：与对照相比，郑58及TS141在干旱胁迫下幼苗的苗长、鲜重、干重明显降低，郑58分别下降18.49%、29.06%和20.00%，TS141分别下降25.66%、23.97%和13.64%；叶片丙二醛（MDA）及过氧化氢（H₂O₂）含量明显增高，MDA含量分别提高了164.58%、263.53%，H₂O₂分别提高了134.95%、203.83%；超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化酶（APX）活性增加，郑58分别提高了65.61%、29.48%、68.49%、141.51%，TS141分别提高了63.01%、48.00%、85.68%、204.29%；叶绿素含量降低，分别降低33.46%、 42.26%；光合参数P_n、G_s、T_r下降，郑58的P_n、G_s、T_r分别下降48.78%、45.31%、52.39%，TS141的P_n、G_s、T_r分别下降57.66%、57.46%、65.14%；抗氧化酶基因SOD3、POD3、CAT1相对表达量提高，郑58分别提高54.58%、34.12%、69.70%，TS141分别提高54.95%、21.36%、59.34%。喷施25 mg·L^-1的5-ALA能明显缓解干旱胁迫对玉米幼苗造成的损伤，与PEG处理相比，玉米自交系郑58和 TS141的幼苗苗长、鲜重、干重明显增加，苗长分别增加了13.31%和11.21%，幼苗鲜重分别增加了22.29%和18.23%，幼苗干重分别增加了16.67%和10.53%；叶片中MDA含量分别降低了17.85%、25.39%，H₂O₂含量分别降低了23.26%、19.15%；SOD、POD、CAT和APX活性进一步增加，郑58分别增加16.49%、18.15%、36.98%和28.13%（P＜0.05），TS141分别增加16.65%、16.54%、28.49%和26.76%（P＜0.05）；叶绿素含量和光合参数P_n、G_s、T_r增加，叶绿素含量分别增加18.29%、19.87%；光合参数P_n分别增加35.87%、42.12%，G_s分别增加36.63%、36.81%，T_r分别增加37.67%、67.88%;玉米幼苗叶片中抗氧化酶基因SOD3、POD3、CAT1相对表达量较干旱胁迫处理都有进一步提高,郑58分别提高20.99%、32.18%和23.51%，TS141分别提高25.97%、23.16%和40.94%。

Effects of exogenous 5-ALA on growth of maize seedlings and expression of antioxidant enzyme genes under drought stress

In this study, drought\|resistant maize inbred line Zheng 58 and drought\|sensitive maize inbred line TS141 were used as materials to study the alleviating effect of 5-aminolevulinic acid (5-ALA) on the effect of maize seedling growth and antioxidant enzyme gene expression under 15% PEG-6000 simulated drought stress. The results showed that compared with the control, the seedling length, fresh weight and dry weight of maize inbred line Zheng 58 and drought sensitive TS141 decreased obviously under drought stress. Zheng 58 decreased by 18.49%, 29.06% and 20.00% respectively, and TS141 decreased by 25.66%, 23.97% and 13.64% respectively. The contents of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) in leaves increased significantly. The content of MDA increased by 164.58% and 263.53% respectively, and the content of H₂O₂ increased by 134.95% and 203.83% respectively. The activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbic acid peroxidase (APX) increased, and Zheng 58 increased by 65.61%, 29.48%, 68.49% and 141.51% respectively, and TS141 increased by 63.01%, 48.00% and 63.01% respectively. Chlorophyll content decreased by 33.46% and 42.26% respectively. P_n, G_s and T_r of Zheng 58 decreased by 48.78%, 45.31% and 52.39% respectively, while those of TS141 decreased by 57.66%, 57.46% and 65.14% respectively. The relative expression of antioxidant enzymes SOD3, POD3 and CAT1 increased, and Zheng 58 increased by 54.58%, 34.12% and 69.70% respectively, and TS141 increased by 54.95%, 21.36% and 59.34% respectively. Spraying 25 mg·L^-1 5-ALA obviously alleviated the damage of maize seedlings caused by drought stress. Compared with PEG treatment, the seedling length, fresh weight and dry weight of maize inbred lines Zheng 58 and TS141 increased significantly, with the seedling length increased by 13.31% and 11.21%, the fresh weight increased by 22.29% and 18.23%, and the dry weight increased by 16.67 respectively. In leaves, MDA decreased by 17.85%, 25.39% and H₂O₂ decreased by 23.26%, 19.15% respectively. The activities of SOD, POD, CAT and APX increased further, Zheng 58 increased by 16.49%, 18.15%, 36.98% and 28.13% respectively, and TS141 increased by 16.65%, 16.54%, 28.49% and 26.76% respectively. Chlorophyll content and photosynthetic parameters P_n, G_s and T_r increased, and chlorophyll content increased by 18.29% and 19.87% respectively. Photosynthetic parameters P_n increased by 35.87% and 42.12%, G_s by 36.63% and 36.81%, and T_r by 37.67% and 67.88%, respectively. Compared with drought stress treatment, the relative expression levels of antioxidant enzyme genes SOD3, POD3 and CAT1 in maize leaves were further increased, Zheng 58 increased by 20.99%, 32.18% and 23.51% and TS141 increased by 25.97%, 23.16% and 40.94% respectively.