温度胁迫对马铃薯叶片抗坏血酸代谢系统的影响

采用盆栽试验，研究了高温（40 ℃）和低温（5 ℃）胁迫下，马铃薯叶片抗坏血酸（AsA）含量、L-半乳糖-1,4-内酯脱氢酶（GalLDH）和脱氢抗坏血酸还原酶（DHAR）基因表达与相应酶活性，以及抗坏血酸过氧化物酶（APX）、单脱氢抗坏血酸还原酶（MDHAR）、谷胱甘肽还原酶（GR）活性及H₂O₂和丙二醛（MDA）含量的变化规律，探讨温度胁迫对AsA代谢系统的影响.结果表明：40 ℃下，AsA含量快速增加，在6 h达到最高值,最高值比对照增加43.7％，而后急速减少；5 ℃下，在9 h达到最高值，最高值比对照增加27.7％，而后也开始减少.GalLDH、DHAR、APX、MDHAR和GR活性在40 ℃和5 ℃下均呈先升后降的变化趋势；GalLDH和DHAR基因表达与其酶活性的变化趋势一致.温度胁迫下，H₂O₂和MDA含量均显著增加.说明在温度胁迫初期，马铃薯叶片以AsA为核心的抗氧化系统对抵御高温和低温胁迫发挥了重要作用，但是随着胁迫时间的延长，AsA代谢系统的抗氧化功能逐渐降低.

Effects of high-and low temperature stresses on ascorbic acid metabolism system in potato leaves

In order to investigate the responses of aseorbic acid (AsA) metabolism system in potato leaves to high and low temperature stresses, a pot experiment was conducted with potato plants exposed to 40 ℃ or 5 ℃, with the leaf AsA content, mRNA expression level of GalLDH and DHAR genes, activities of GalLDH, DHAR, APX, MDHAR and GR, and contents of hydrogen peroxide (H_2O_2) and malondialdehyde (MDA) determined. Under the exposure to 40 ℃, the leaf AsA content increased rapidly and reached the highest (43.7% higher than the control) at 6 h, followed by a rapid decrease. Under the exposure to 5 ℃, the AsA content also increased first, reached the highest (27. 7% higher than the control) at 9 h, and then decreased. Under the two temperature regimes, the activities of leaf GalLDH, DHAR, APX, MDHAR and GR decreased after an initial increase, the mRNA expression level of GalLDH and DHAR genes showed the similar changes with their corresponding enzyme activities, and the leaf MDA and H_2O_2 contents increased remarkably after 24 h. All the results suggested that the AsA metabolism system in potato leaves was stimulated in the early period of high- and low temperature stresses, but its function declined gradually with the duration of the stresses.