Kumar GNM., Knowles N. R.
Department of Plant Science, 4-10 Agriculture/Forestry Centre, University of Alberta, Edmonton, Alberta, Canada T6G 2P5.
Plant Physiol. 1993 May;102(1):115-124. doi: 10.1104/pp.102.1.115.
Previous research has shown that cell membranes of potato (Solanum tuberosum L. cv Russet Burbank) seed-tubers lose integrity between 7 and 26 months of storage (4[deg]C, 95% relative humidity), and this loss coincides with a significant decrease in growth potential. The age-induced decline in membrane integrity is apparently due to increased peroxidative damage of membrane lipids. Malondialdehyde (MDA) and ethane concentrations (sensitive markers of lipid peroxidation and membrane damage) increased in seed-tuber tissues with advancing age. Moreover, in vivo ethane production from discs of cortex tissue from 13- and 25-month-old seed-tubers was 87% greater (on average) than that from discs from 1-month-old tubers. Calcium suppressed ethane production from all ages of tissue discs, and the effect was concentration dependent. Linoleic acid enhanced ethane production from 5- and 17-month-old tubers by 61 and 228%, respectively, suggesting that older tissue may contain a higher free-radical (FR) titer and/or lower free polyunsaturated fatty acid content. In addition, throughout plant establishment, the internal ethane concentration of older seed-tubers was 54% higher than that of younger seed-tubers. MDA concentration of tuber tissue declined by about 65% during the initial 7 months of storage and then increased 267% as tuber age advanced to 30 months. The age-induced trend in tuber reducing sugar concentration was similar to that of MDA, and the two were linearly correlated. The age-dependent increase in reducing sugars may thus reflect peroxidative degeneration of the amyloplast membrane, leading to increased starch hydrolysis. Compared with 5-month-old seed tubers, 17- and 29-month-old seed-tubers had significantly higher levels of lipofuscin-like fluorescent compounds (FCs), which are produced when MDA reacts with free amino acids. Age-dependent increases in MDA, ethane, and FCs were not associated with higher activities of phospholipase and lipoxygenase in tissue from older tubers. In fact, 8-month-old seed-tubers had significantly higher activities of these enzymes than 20-month-old seed-tubers. However, the activities of superoxide dismutase, peroxidase, and catalase in 20-month-old tubers were substantially higher out of storage, and increased at a faster rate during plant establishment, than in 8-month-old seed-tubers. Collectively, these results suggest that a gradual build-up of FRs leads to peroxidative damage of membrane lipids during aging of potato seed-tubers.
先前的研究表明，马铃薯（Solanum tuberosum L. cv Russet Burbank）种薯的细胞膜在储存7至26个月（4℃，相对湿度95%）期间会失去完整性，这种损失与生长潜力的显著下降同时发生。年龄诱导的膜完整性下降显然是由于膜脂过氧化损伤增加所致。随着种薯组织年龄的增长，丙二醛（MDA）和乙烷浓度（脂质过氧化和膜损伤的敏感标志物）增加。此外，13个月和25个月龄种薯的皮层组织圆盘在体内产生的乙烷量平均比1个月龄块茎的圆盘高87%。钙抑制了所有年龄组织圆盘的乙烷产生，且这种作用呈浓度依赖性。亚油酸分别使5个月和17个月龄块茎的乙烷产生量增加了61%和228%，这表明较老的组织可能含有更高的自由基（FR）滴度和/或更低的游离多不饱和脂肪酸含量。此外，在整个植株生长过程中，较老种薯的内部乙烷浓度比较年轻种薯高54%。块茎组织的MDA浓度在储存的最初7个月内下降了约65%，然后随着块茎年龄增长到30个月而增加了267%。块茎还原糖浓度随年龄变化的趋势与MDA相似，且二者呈线性相关。因此，还原糖随年龄的增加可能反映了造粉体膜的过氧化退化，导致淀粉水解增加。与5个月龄的种薯相比，17个月和29个月龄的种薯具有显著更高水平的脂褐素样荧光化合物（FCs），当MDA与游离氨基酸反应时会产生这些化合物。MDA、乙烷和FCs随年龄的增加与较老块茎组织中磷脂酶和脂氧合酶的较高活性无关。事实上，8个月龄的种薯这些酶的活性显著高于20个月龄的种薯。然而，20个月龄块茎中超氧化物歧化酶、过氧化物酶和过氧化氢酶的活性在储存后显著更高，并且在植株生长过程中比8个月龄的种薯增加得更快。总的来说，这些结果表明自由基的逐渐积累导致马铃薯种薯衰老过程中膜脂的过氧化损伤。
