辣椒成熟过程中贮藏物质变化的显微化学与电镜观察

Microchemical and Ultramicroscopic Observation on Dynamics of Storage Reserves in Chili Pepper Fruits During Ripening

为了解辣椒果实成熟过程中果皮内贮藏物质的变化模式,用光学和透射电子显微技术对绿色和成熟变红果皮进行显微化学和超微结构观察。结果表明,果实充分膨大并且仍呈绿色时,中果皮的薄壁组织和内果皮含大量淀粉粒,中果皮的厚角组织及外果皮无淀粉。果实成熟变红后,淀粉粒消失,果皮积累两种脂滴,外果皮积累质体脂滴,中果皮及内果皮积累质体脂滴和胞质脂滴;胞质脂滴椭球形,存在于细胞质中,沿质膜内表面排列,质体脂滴球形和棒状,存在于有色体中;外果皮中质体脂滴以球形为主,中果皮和内果皮中质体脂滴以棒状为主;胞质脂滴和质体脂滴都与四氧化锇反应,显示脂肪酸链含有双键。归纳起来,果实成熟前,果皮中的贮藏物质是淀粉粒,淀粉积累有组织特异性,只在中果皮的薄壁组织和内果皮中积累;果实成熟变红后,贮藏物质转化成胞质脂滴和质体脂滴,质体脂滴存在于所有组织,而胞质脂滴不存在于外果皮;辣椒油富含不饱脂肪酸。

In order to understand the dynamics of storage reserves in chili pepper fruits during ripening,pericarps of green and red fruits were examined by means of histochemistry and transmission electron microscopy. As fruits fully expanded and remained green,the endocarp and the parenchyma of the mesocarp contained a large number of starch grains,while the epicarp and the collenchymas of the mesocarp lacked storage reserves. As fruits ripened to red,starch grains disappeared,a large number of plastidial lipid droplets accumulated in the epicarp,and both plastidial and cytosolic lipid droplets accumulated in great numbers in other tissues. Cytosolic lipid droplets were elliptical and were located in the cytoplasm,whereas the plastidial lipid droplets were spherical or rod-like and located within chromoplasts that occurred in all tissues. Spherical plastidial lipid droplets tended to be present in the epicarp,whereas rod-like lipid droplets tended to be present in other tissues. Both cytosolic and plastidial lipid dropletsstrongly reacted with osmium tetroxide to produce orange color,indicating the presence of double bonds. In summary,the storage reserves in green pericarp were starch grains that were exclusively present in the parenchyma of the mesocarp and endocarp,and the storage reserves were converted to cytosolic and plastidial lipid droplets as the fruits ripened to red. Plastidial lipid droplets accumulated in all tissues,while cytosolic lipid droplets were absent in the epicarp. All lipid droplets contained unsaturated oil.