外源一氧化氮对低温胁迫下枇杷叶片AsA-GSH循环的影响

采用0.2、0.5、1.0和1.5 mmol·L^-1的硝普钠(SNP)处理3年生‘早钟6号’枇杷幼苗，以喷清水为对照(CK)，于-3 ℃低温胁迫处理6 h后在25 ℃下培养4 d，测定恢复0、1和4 d时叶片非酶抗氧化物质和抗氧化酶活性的变化.结果表明：与CK相比，经SNP处理的枇杷叶片过氧化氢(H₂O₂)含量降低，还原型谷胱甘肽(GSH)和抗坏血酸(AsA)含量及抗坏血酸过氧化物酶(APX)、谷胱甘肽还原酶(GR)、脱氢抗坏血酸还原酶(DHAR)和单脱氢抗坏血酸还原酶(MDAR)活性升高.低温处理后恢复4 d时，经0.5 mmol·L^-1 SNP处理的枇杷叶片H₂O₂含量下降至CK的75.3%，而GSH和AsA含量分别比CK增加了29.12%和23.40%，APX、GR、DHAR和MDAR活性分别比CK增加了50.0%、44.4%、49.53%和62.68%.适当的外源NO处理可提高枇杷叶片的抗氧化系统活性，减轻细胞在低温胁迫下的损伤，其中以0.5 mmol·L^-1的SNP处理效果较理想.

Effects of exogenous NO on ascorbate-glutathione cycle in loquat leaves under low temperature stress.

Three-year-old ‘Zaozhong No. 6’ loquat (Eriobotrya japonica Lindl.) seed lings were foliar-sprayed with 02, 05, 10 and 15 mmol·L-1 o f sodium nitroprusside (SNP), subjected to low temperature (-3 ℃) stress for 6 hours, and then cultured at 25 ℃ for four days. The antioxidant metabolites and enzymes in the seedling leaves were determined 0, 1, and 4 days after recovery. Comparing with the control (water spraying), all SNP treatments had a decreased H2O2 content but an increased content of glutathione (GSH) and ascorbic aci d (AsA) and increased activity of ascorbate peroxidase (APX), glutathione reduct ase (GR), dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase ( MDAR) in the seedling leaves. Four days after recovery, the H2O2 content in the seedling leaves treated with 05 mmol·L-1 of SNP decreased by 7553 %, while the GSH and AsA contents and the APX, GR, DHAR and MDAR activities were increased by 2912%, 2340%, 500%, 444%, 4953%, and 6268%, respectivel y. All of these suggested that appropriate dosage of exogenous NO could enhance the activity of antioxidant system in loquat leaves and alleviated the cell inju ry of loquat leaves under low temperature stress. In this study, the appropriate dosage of NO was 05 mmol·L-1 of SNP.