柑橘果实遮光处理对发育中的果实光合产物分配、糖代谢与积累的影响

研究了柑橘果实膨大初期遮光处理对果皮色素、果实含糖量、光合产物在果实内的分配及果实中蔗糖代谢相关酶活力变化的影响.结果表明遮光处理使果皮中的叶绿素含量迅速降低而类胡萝卜素积累缓慢,蔗糖的相对含量则明显上升.遮光处理还促进了光合产物向果皮运输,相应地降低了汁囊中光合产物分配比率,使果实汁囊中蔗糖含量下降.果皮中SS、SPS和转化酶活力在遮光处理后均有较大的提高,而汁囊中则差异不大.上述结果表明,在果实自身光合作用被抑制的条件下,果皮是通过提高酶活力来增强库强度,从而使其在与汁囊竞争中获得更多的光合产物,造成汁囊含糖量下降.

Effects of Fruit Shading on Photosynthate Partitioning, Sugar Metabolism and Accumulation in Developing Satsuma Mandarin (Citrus unshiu Marc. ) Fruit

The physiological effects of fruit shading by covering fruit with two layer opaque paper bag at the primary stage of fruit enlargement were investigated in developing satsuma mandarin fruit. Compared with control fruit, the chlorophyll in peel dropped rapidly and the accumulating rate of carotenoid in peel was very slow throughout fruit development(Fig.3). The total sugar content of peel in shaded fruit was lower but the relative content of sucrose in peel was significantly higher than that in control fruit(Fig.1). Fruit shading increased the percentage of photosynthates partitioning to peel, and correspondingly decreased the percentage of photosynthates partitioned to juice sacs(Fig.4). Fruit shading also reduced the sucrose content of juice sacs in developing satsuma mandarin fruit(Fig.2). The activities of sucrose synthase(SS), invertase and sucrose phosphate synthase(SPS) in peel of shaded fruit were much higher than those of control fruit, but fruit shading had almost no effects on the activities of sucrose metabolizing enzyme in juice sacs(Figs.5-7). These results indicate that in the absence of fruit photosynthesis, the sink strength of peel was strengthened by elevating activities of sucrose metabolizing enzymes in this tissue, thus leading to division more photosynthates to peel and corresponding decrease of sugar content in juice sacs of satsuma mandarin.