冷藏苹果阴阳面果皮超微结构和虎皮病的发生

ULTRASTRUCTURAL STUDY OF THE SUNNY-SIDE AND SHADED SIDE PEELS OF THE COLD-STORED APPLE FRUITS AND SUPERFICIAL SCALD DEVELOPMENT

用电镜观察了在0℃贮藏4个月和在20℃室温发病后红星苹果(Mains p1L’,llLtl ill。)阴阳面果皮的超微结构。发现苹果果实角质层中电子密集物与虎皮病的发生有密切关系。该电子密集物可由角质层沿细胞壁向内层细胞移动,在接触到细胞时细胞质膜解体,内部结构破坏,并可进人细胞内部,增大细胞的电子密度。推测该电子密集物可能是a一法尼烯氧化反应后的混合物。冷藏结束时,果实阴阳面均无虎皮病发生。果实阳面细胞内部结构较好,内层细胞胞壁电子密集物少,而果实阴面有的表皮细胞已解体,内层细胞胞壁电子密集物多。在果实阴面发病后,阳面仍未发病。果实阳面细胞内部结构仍较好,只少数下皮外层细胞被破坏,而果实阴面果皮细胞已解体,电子密度增加。研究认为,角质层中电子密集物可从表皮、下皮细胞外部伤害细胞。

Ultrastructure of the sunny-side and the shaded side peels of the apple (Malus putrdla Mill.) fruits stored at 0℃ for 4 months and later developed scald at 20℃ were observed by electron microscopy. It was found that electron dense materials (EDM) in the apple cuticle was strongly correlated with scald development. EDM could move from cuticle to inner cells along the cell walls. The accumulation of EDM on the cells could cause the breakage of plasmalemma and damage internal structure. The EDM could move into the cell as the cell collapsed. It was assumed that EDM could be a compound product of oc-farnesene oxidation in the cuticle. At the end of cold storage, no scald developed on both the sunny-side and the shaded side peels of apples. Little EDM was found in the walls of outer hypodermal cells of the sunny-side fruit peel in which the cells maintained their healthy structure, but some epidermal cells in the shaded side fruit peel were destroyed by EDM. It was also found that much EDM existed in the walls of outer hypodermal cells. There was no scald symptoms develop on the sunny-side peel after the shaded side peel of the fruit severely scalded at 20 t. Only a few cells in the outer hypodermis of the sunny-side peel of the fruit were damaged by EDM, most of the cells maintained their healthy structure, but all of the cells in the shaded side peel of the fruit were destroyed and electron-dense was increased. It was suggested that the epidermal and hypodermal cells were damaged by EDM in the cuticle from outside of the cells.