摘要
测定了温州蜜柑果实发育进程中糖的积累动态 ,并用14 C示踪方法研究了果实发育不同阶段源叶的光合产物在果实中的运输分配特性。结果表明 :⑴果实组织中的糖含量随果实发育持续上升 ,果皮以积累己糖为主而其它组织则以积累蔗糖为主或略多。⑵在果实完熟之前 ,汁囊分配到的光合产物均占果实的5 0 %以上 ,为果实中的光合产物分配中心 ;而到完熟阶段分配到汁囊的14 C光合产物与其它组织接近 ,不再有明显的分配中心。⑶汁囊中的14 C放射性比活度随着果实发育呈下降趋势 ,尤其在后期下降极为明显。⑷维管束 /囊瓣表皮和囊瓣表皮 /汁囊的14 C放射性比活度的比率都随果实发育进程而增大 ,但后者的比率要大大高于前者 ,表明韧皮部后运输是光合产物进入汁囊的限速阶段。⑸输入到汁囊的14 C光合产物主要以蔗糖形式存在 。
Characteristics of photosynthate translocation, partitioning and sugar accumulation were investigated in developing fruit of satsuma mandarin ( Citrus unshiu Marc.). In 14 C tracing experiment, the source leaf next to a sample fruit was exposed to 14 CO 2 under daylight for 1 h, then allowed to stay in ambient air for 5 h, 23 h or 47 h. Peel, vascular bundles and phloem free tissues in the fruit quarter directly aligned with the source leaf were isolated by dissection for chemical and radioactivity analysis. Radioactivity was quantified after separation and extraction of the tissues in boiling 80% ethanol. The following results were obtained. ⑴ Sugar content of the fruit tissues increased with fruit development. In the peel, nearly equal amounts (in mg/g FW) of sucrose, fructose and glucose occurred in the peel and the accumulation patterns of these sugars were quite similar. In other tissues, however, sucrose level was substantially or moderately higher than that of total hexoses (Fig.1). ⑵ Over 50% of the photosynthates transported to fruit was found in juice sac at the primary stage of fruit enlargement, stage of rapid fruit enlargement and fruit coloring. At the full ripe stage, however, the amount of photosynthate obtained by juice sac was about the same as that entering peel, vascular bundle and segment epidermis (Fig.2). ⑶Specific 14 C radioactivity acquired by juice sac markedly decreased with fruit development, especially at the latest stage (Fig.3). ⑷ Specific 14 C radioactivity ratios of vascular bundle to segment epidermis and segment epidermis to juice sac considerably increased with the progress of fruit development, the latter ratio being much higher (Table 1). This result suggests that postphloem assimilate transport was the limiting step in the pathway for assimilate transfer into juice sac. ⑸The fact that a certain percentage of 14 C sugars recovered in juice sacs was sucrose indicates that although photosynthates were partially hydrolyzed during their transfer into juice sac, at least part of photosynthates in the form of sucrose could still enter the juice sacs unchanged (Table 2).
基金
国家自然科学基金重点资助项目
批准号为 3 973 0 3 4 0
关键词
温州蜜柑
光合产物运输
分配
糖积累
果实发育
Citrus unshiu , photosynthate translocation, photosynthate partitioning, sugar accumulation
