Responses of apple fruit to low O2 concentrations involved in membrane lipid metabolism
Y.M. Jiang, J. Streif, A.A. Saquet, F. Bangerth
ISHS Acta Horticulturae 599: 505-511.
2003
บทคัดย่อ
Experiments were conducted to determine levels of low O2 exposure needed to prevent the occurrence of abnormal respiration, and to characterise the relationship between respiration and membrane lipids of apple fruit. The membrane lipid-associated lipase activity was also measured. Exposure of ‘Braeburn’ apples to 3% and 6% O2 at 10°C markedly reduced CO2 production relative to 21% O2; however, CO2 production rapidly increased when O2 level was further reduced to 1.5 or even 0%, due to anaerobic respiration. Free fatty acids were high in fruits exposed to air atmosphere for 4 days and decreased gradually with the exposure period, whereas a delay in the increase of the fatty acids was observed exposed to 6 or 3% O2 within 12 days. Compared to 6 or 3%, exposure of apples to 1.5 or 0% resulted in higher content of the fatty acids. Furthermore, among these fatty acids analysed, the largest amount was palmitic acid, followed by stearic acid. The change in lipase activity had similar patterns, but a rapid increase in the enzyme activity coincident with the higher content of the fatty acids occurred in apples exposed to 21 or 0% O2 for 4 days. In contrast to the fatty acids, there were more dramatic changes in the fatty acid composition of polar lipids when apples were exposed to various O2 concentrations. Exposure to 6 or 3% O2 exhibited a better maintenance of membrane lipid composition, as judged by relatively stable saturated/unsaturated fatty acid ratios in combination with respiration rates throughout this experiment. The results suggested that responses of apples to reduced O2 concentrations are involved in the breakdown and modification of membrane lipids which may further influence respiratory patterns.