【作者】 陈俊伟；

【导师】 张上隆； 张良诚；

【作者基本信息】 浙江大学 ， 果树学， 2002， 博士

【摘要】 柑橘为我国重要果品之一。由于近年来我国瓜果产量全面增长，果品生产已由供求基本平衡变为局部供过于求。随着我国加入WTO，柑橘将面临着市场国际化的激烈竞争，优质柑橘生产已是迫在眉睫。在构成柑橘品质的诸多因子中，含糖量是重要指标之一。糖不仅是影响果实甜度的物质，而且还是酸、类胡萝卜素和其它营养成分及芳香物质合成的基础原料。因此研究柑橘果实糖运输与积累过程，可以搞清果实内的糖运输、代谢与积累的生理机制，为科学调控柑橘品质打下基础。 本研究以温州蜜柑（Citrus unshui Marc）为试材，对果实发育进程中果皮、维管束、囊瓣表皮和汁囊等组织的干鲜重、葡萄糖、果糖及蔗糖的积累特性，果实发育不同阶段源叶与果实同化的光合产物在果实内各组织间的运输分配特点，果实发育进程中果皮光合速率与叶绿素含量的变化及果实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和果实中蔗糖代谢相关酶活力变化的影响，和果实膨大期和完熟期内蔗糖在柑橘果实内的运输机制等四个方面进行了初步研究。主要结果如下： 1) 果实组织中的糖含量、干鲜重均随果实发育持续上升，果皮以积累己糖为主而汁囊、囊瓣表皮、维管束等组织则以积累蔗糖为主或略多。 2) 在果实完熟之前，即使是当果皮积累的干重超过汁囊时，叶同化产物仍主要分配到汁囊中；汁囊分配到的光合产物均占果实获得¹⁴C总量的50％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¹⁴C光合产物与其它组织接近，不再有明显的分配中心。 3) 对从维管束到汁囊运输过程中的¹⁴C光合产物进行薄层层析分析表明至少75％以上的¹⁴C光合产物以蔗糖形态存在，说明光合产物是以蔗糖为主体运输并输入汁囊参与糖积累和代谢的。 4) 汁囊中的¹⁴C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。维管束／囊瓣表皮和囊瓣表皮／汁囊的¹⁴C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。 5) 对果实光合作用及果实同化产物在果实内的分配表明，果皮光合速率与叶绿素含量有关，随着叶绿素含量的下降，果实光合速率也快速下降。果皮的同化产物，主要保留在果皮中，输入到汁囊的比率随果实发育而下降， 但高峰时也有 12％输入汁囊。与对照相比，果实遮光处理后降低了果皮与 汁囊的干重和含糖量。上述结果表明果皮光合产物主要用于果皮自身的发 育并能减少对叶光合产物的依赖，同时也能部分增加汁囊糖的积累。 6)采用不透光双层纸袋遮光以抑制果实光合作用的实验结果表明，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减慢，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，相应地降低光合产 物分配到汁囊中的比率，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，而汁囊中则与对照差异不大。 上述结果表明，在果实自身光合作用被抑制的条件下，果皮能通过提高酶活 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。 刀 以果实薄片、囊瓣薄片和汁囊为试材研究了载体抑制剂和ATP酶抑制剂 对果实各组织’℃蔗糖吸收的影响，结果表明：PCMBS、DNP、EB和 NO。“ 处理明显抑制汁囊对‘℃－蔗糖的吸收，而用果实薄片、囊瓣薄片作’℃－蔗 糖吸收材料仅只有EB对蔗糖的吸收有抑制效应。由此可见，蔗糖在柑橘 果实汁囊细胞中运输即韧皮部后运输存在一个载体介导的依赖于能量的 主动运输过程。更多还原

【Abstract】 Citrus is one of the most important fruits in China. With general increase in yields of all kinds of fruits and melons, the fruit production in our country has changed from a situation where supply and demand were basically balanced to an excess of supply over demand. After entry of China into WTO, our domestic citrus market will surely face the competition from abroad. Therefore, the breeding and production of high quality citrus fruit is urgent. Sugars play an essential part in flavor characteristics of the citrus fruit and are also a commercial measure of fresh fruit quality. Sugars are not only the substance that affect sweetness of fruit, but also form the material basis for synthesis of organic acids, carotenoids, and other nutrient and aromatic ingredients of citrus fruit. Studying sugar transporting and accumulating process in tissues of developing citrus fruit will supply an important basis for elucidating the mechanism of sugar transporting, metabolism and accumulation and is beneficial to scientific regulating citrus quality.To clarify the mechanism of sugar translation, partitioning and accumulation in citrus fruit, we studied the following physiological aspects of developing fruit using satsuma mandarin (Citrus unshiu Marc. cv. Miyagawa wase). (1) The trends of glucose, fructose, sucrose, dry weight, and fresh weight accumulation in various tissues at different stage fruit development. (2) Translocation and partitioning of leaf- and fruit-derived photosynthates in tissues of developing fruit. (3) Change in rate of peel photosynthesis and peel chlorophyll content and effects of fruit shading on peel pigment content, sugar content, partitioning of photosynthates within fruit and activity of sucrose metabolizing-enzyme in developing fruit. (4) The mechanism of postphloem sucrose transport in developing fruit. The results were summarized below.1) Sugar content and dry- or fresh weight of the fruit tissues increased steadily in the course of fruit development. In the peel, nearly equal amounts (in mg/g FW) of sucrose, fructose and glucose occurred in the peel and similar accumulation patterns of these sugars were observed. In juice sacs, segment epidermis and vascular bundles, however, sucrose level was substantially or moderately higher than that of total hexoses.2) Over 50% of the photosynthates transported to fruit were deposited in juice sacs at the primary stage of fruit enlargement, stage of rapid fruit enlargement and stage of fruit coloring even when the dry weight of peel exceeded that of juice sacs. At the full ripe stage, however, the amount of photosynthate obtained by juice sacs was about the same as that entering peel, vascular bundle or segment epidermis.3) Analysis of ethanol soluble I4C-photosynthates of various fruit tissues by TLC showed that over 75% of 14C-sugars recovered in fruit tissues were sucrose. This results suggested that most of photosynthates is transported as the form of sucrose within fruit, and most of photosynthates is in the form of sucrose entering into juice sacs where they were accumulated and metabolized.4) Specific I4C radioactivity acquired by juice sacs markedly decreased with fruit development, especially at the latest stage. Ratios of Specific MC radioactivity of vascular bundle to that ofsegment epidermis and of segment epidermis to that of juice sacs considerably increased with the1 progress of fruit development, the latter ratio being much higher. This result suggests thatpostphloem assimilate transport was the limiting step of assimilate translocation in the fruit.5) Peel photosynthetic rate and chlorophyll content, and the characteristics of translocation and distribution of radiolabelled assimilates within fruit were examined from primary stage of fruit enlargement up to fruit full ripe. Change in fruit photosynthetic rate was related to change in peel chlorophyll content. Fruit photosynthetic rate markedly declined as the fruit grew and chlorophyll degraded in peel. Before the fruit full ripe stage, photosynthates produced更多还原