脱水速率对黄皮胚轴脱水敏感性及膜脂过氧化的影响

Effects of Drying at Different Rates on Desiccation Sensitivity and Membrane Lipid Peroxidation in Chinese Wampee [Clausena lansium (Lour.) Skeels] Axes

以黄皮种子离体胚轴为材料 ,研究了不同干燥速率对胚轴脱水反应和膜脂过氧化的影响。在脱水过程中 ,胚轴的萌发率、活力指数、电解质渗漏速率 ,超氧化物歧化酶 (SOD)、过氧化物酶 (POD)和过氧化氢酶 (CAT)活性逐渐降低 ,膜脂过氧化产物MDA的含量不断增加。脱水速率愈快 ,胚轴的半致死含水量就愈低。快速干燥的胚轴能在较低的含水量下存活是因为缩短了在中间含水量下发生的膜脂过氧化作用的时间 ,以及保持较高的SOD、POD和CAT活性 ;缓慢干燥的胚轴当与周围环境达到水分平衡后 ,生活力的丧失将与保持在水分平衡后的时间有关。因此 。

Excised axes from Chinese wampee [ Clausena lansium (Lour.) Skeels] seeds were used as materials, and effects of drying at different rates on dehydration response and peroxidation of membrane lipid in axes were studied. During dehydration, the tolerance of axes to desiccation which was analyzed as germination percentage, vigour index, and rate of electrolyte leakage (Figs.1,2), and activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) (Fig.3) gradually decreased, the content of malondialdehyde (MDA), a product of membrane lipid peroxidation, progressively increased (Fig.4). It has been found that the more rapidly the dehydration of axes is achieved, the lower the water content at which 50% of axes were killed by dehydration is. Flash dried axes can survive lower water contents because the time when aqueous based membrane lipid peroxidation occurred was significantly shortened at intermediate water contents and higher activities of SOD, POD and CAT remained at lower water contents (Fig.3). After the equilibrium water contents between slowly dried axes and ambient relative humidity were reached, the loss of viability were associated with the duration the axes are kept at that water content. The dehydration at different rates, therefore, is an important factor which influences desiccation sensitivity of recalcitrant seeds or axes.