间歇低温胁迫对桃果实细胞壁代谢的影响

桃果实在成熟过程中细胞壁干物质不断减少,随着共价结合果胶质和离子结合果胶质减少,水溶性果胶质明显增加,纤维素也逐渐减少,但半纤维素含量变化较小.低温胁迫造成果胶质和纤维素的降解过程受阻,从而造成较高分子量果胶质的积累,果汁粘度升高.中途加温则能促进果胶质和纤维素的增溶和解聚,引导细胞进行与果实成熟有关的细胞壁代谢.14C-蔗糖标记试验表明,在细胞壁不断降解的同时,也进行着合成.在果实成熟的启动阶段,细胞壁的合成能力加强.果实衰老过程与细胞壁合成减少有着直接的联系.受到低温伤害的果实细胞壁物质含量高于正常果实的原因,并不是其合成水平的升高,而是其降解的减慢.

Influence of Intermittent Low Temperature Stress on Cell Wall Metabolism in PeachesMAO Lin-Chun

During normal ripening the dry weight of the total cell wall material decreased, while water soluble pectin content increased extensively with the decrease in amounts of ionically associated and covalently bound pectins and cellulose (Figs.1,2). However, hemicellulose content did not change significantly. Low temperature stress slowed down degradation of pectin and cellulose, causing accumulation of high molecular weight pectin and increase in juice viscosity (Fig.1). Intermittent warming resulted in solubilization and depolymerization of pectins and cellulose (Fig.3), thus leading to cell wall metabolism associated with fruit ripening. Radiolabeling test using 14 C sucrose indicated that cell wall synthesis continued during the degradation of cell wall, and increased during the onset of fruit ripening (Fig.4). Fruit senescence was directly associated with reduced cell wall synthesis. The higher amount of cell wall material in chilling injured fruit than that in normal fruit was not due to an increase in cell wall synthesis but rather to a reduced degradation of cell wall material.