【作者】 杨子琴；

【导师】 孙守如；

【作者基本信息】 河南农业大学 ， 蔬菜学， 2008， 硕士

【摘要】 南瓜在我国种植范围之广不亚于任何一种蔬菜作物,它具有很高的营养价值和较高的医疗保健作用,在改善饮食习惯和膳食结构方面起到了重要的作用。但我国南瓜品质相对较差,经济效益不高。随着我国经济国际化进程的加快,南瓜消费市场将面临国际化的竞争,提高南瓜果实品质的任务已十分迫切。同时随着人们生活水平的提高和对健康的重视,消费者对南瓜品质的要求也越来越高。而糖分、淀粉和β-胡萝卜素的含量是南瓜品质构成的重要指标。尤其含糖量不仅影响果实的甜度和着色,还是合成有机酸、维生素和类胡萝卜素等营养成分的基础原料。因此研究南瓜糖分积累机理对改善果实品质具有重要意义。本研究通过3个不同基因型南瓜果实发育过程中糖分的积累及其代谢酶变化动态模式的比较,研究不同基因型南瓜果实糖分及淀粉积累差异的内在机理,初步明确了南瓜可溶性糖及淀粉的积累模式和可溶性糖及淀粉代谢相关酶在南瓜品质形成中的作用。结果如下:通过对3个不同基因型南瓜的研究发现,“红香栗”果实发育的不同阶段积累营养成分不同,前期主要积累可溶性糖,后期是淀粉的积累阶段。“黄狼”主要在后期积累可溶性糖,淀粉在“黄狼”的整个生长过程都在不断的积累。“蜜本”南瓜在生长的前期主要为淀粉积累阶段,后期为糖分积累阶段。甜度指数以果糖×2+葡萄糖×1+蔗糖×1.45+五碳糖×1.52计算,可知收获时“蜜本”的甜度指数最高,为184.21,“黄狼”的甜度指数为153.84,“红香栗”甜度指数为115.90。果糖对“红香栗”、“黄狼”、“蜜本”果实的甜度指数的贡献分别为54.2%、42.0%和42.8%。就本试验而言,果糖含量水平是引起品种间甜度差异的主要因素;“红香栗”为淀粉积累型南瓜。β-胡萝卜素在3个品种中的累积差别非常大。含量变化都以逐渐增加为主要趋势,但增加幅度以“红香栗”最大,尤其5～6周的增加量为整个生长过程β-胡萝卜素积累总量的70%。“黄狼”在整个生长过程中变化比较缓慢,β-胡萝卜素积累量在3个品种中也最低。“蜜本”β-胡萝卜素为阶段积累型,分别在果实迅速膨大期和成熟前积累。由此可知“红香栗”为高β-胡萝卜素品种。南瓜授粉之后,果肉中主要的可溶性糖为葡萄糖和果糖,在蔗糖积累之前一直是果肉中主要的可溶性糖。“黄狼”和“蜜本”在生长发育过程中各糖分含量相差不多,积累趋势也相似,几乎同步积累。蔗糖的积累均出现在中后期,高蔗糖积累型的“蜜本”在生长的后期积累蔗糖速度快,并且在成熟时有更高的蔗糖含量。“红香栗”在整个生长过程中一直具有高的淀粉积累速度,明显优越于另外两个品种。果实发育前期,蔗糖分解酶类的活性明显大于蔗糖合成酶类,蔗糖代谢相关酶的净活性为较高的负值。因此光合产物进入果实后大多被分解、利用和消耗,蔗糖的积累较缓慢。果实发育中后期,蔗糖代谢相关酶分解酶类活性低于合成酶类活性,故果实中蔗糖的含量迅速增加。果实成熟时蔗糖分解酶类活性与合成酶类活性趋于平衡。本试验结果表明:净活性为负值时只有少量蔗糖积累;净活性为正值后才有蔗糖的积累。“红香栗”蔗糖的积累与SPS和SS活性的升高表现出正相关。随着SPS和SS活性的不断升高蔗糖含量增加。在3个品种中“红香栗”积累蔗糖最低。“黄狼”和“蜜本”在果实发育的前期均有较高的转化酶活性,这导致果肉中含有高浓度的己糖,这些己糖是组织快速生长的碳源,并且高浓度的己糖在果实生长初期对维持细胞内高的渗透压,保证充足的水分吸收具有重要的意义。“黄狼”和“蜜本”蔗糖的积累在生长的中期与SPS和SS活性的升高有关,后期蔗糖含量的升高与酸性转化酶活性的下降表现出极大的相关性。淀粉积累型南瓜“红香栗”淀粉的积累与淀粉磷酸化酶活性关系不大,与蔗糖合成酶活性的变化呈正相关。“蜜本”淀粉积累的初期也表现出与“红香栗”同样的淀粉积累模式。“黄狼”果实后期淀粉的快速积累与淀粉磷酸化酶活性的迅速升高有关。因此我们认为,果实发育后期SPS和SS活性的升高及果实发育后期转化酶活性的降低共同促成了果实中蔗糖的积累。蔗糖合成酶对淀粉积累型果实淀粉的积累起重要作用,淀粉磷酸化酶促成了非淀粉积累型果实中淀粉的积累。更多还原

【Abstract】 Pumpkin was planted not less than any other vegetable crops in our country. Its nutrition value and medical healthe function are very high. And playing an important action at improving people’s bite and sup habit, even at changing our meal configuration. However, the poor quality of pumpkin fruits give rise to a great reduction in the economic benefit. With the development of economic internationalization, the market of pumpkin will face competition internationalization. So it is very urgent to improve the quality of pumpkin fruits. With the increasing living standard and the regarding of the health,there is a large demand for higher quality pumpkin fruits. sugar, starch andβ-Carotene contents are mainly guide line of the quality of pumpkin fruits,especially the contents of sugar. Because it affects the tastes and color of fruit and serve as a precursor as well for synthesis of organic acid, vitamin and carotenoids. Therefore, it is very imperative to study the mechanism of sugar accumulation for the ultimate goal of improving the quality of pumpkin.Three pumpkin varieties were used as research materials. The genotypic difference in sugar-accumulating patterns and its related sucrose metabolizing enzymes were systemically analyzed for elucidating the physiological aspects that are possibly responsible for the difference. The main results were as follows:By comparing three pumpkin genotypes, the result showed that the contents of the nutrition elements increasing were different at different growth stage with the“hongxiangli”fruits growing. At early stage dissolubility sugar was the main accumulation. Evening is the stage of accumulation of starch.“huanglang”accumulate total sugar main at evening. Starch accumulate through the developing fruit of“huanglang”. Starch was the main accumulation at early stage of the developing fruit of“miben”. Evening is the accumulation stage of sugar. According to Fructose×2+Glucose×1+Sucrose×1.45+Pentose×1.52, the sweetness index of“miben”was the highest at maturity. The sweetness index of“miben”was 184.21 and the sweetness index of“huanglang”was 153.84. meanwhile it was 115.90 in“hongxiangli”. The contribution ration of fructose to sweetness index were 54.2% and 42.0% in“hongxiangli”and“huanglang”, meanwhile it was 42.8% in“miben”. These findings suggested that the fructose level was the main determinant of sweetness in different genotypic pumpkin. Pumpkin of“hongxiangli”mainly accumulated starch.Cumulation ofβ-Carotene were varied in three pumpkin varieties. But all of their current were increase mainly, the biggest increse extent is“hongxiangli”in the there varieties, especially during 5～6 weeks, at this stage the accumulation ofβ-Carotene count for 70℅ in this developmental stage, while the cumulation of“huanglang”was slowly in this developmental stage, and was the lowest. It depends on the developmental stage ofβ-Carotene cumulation in“miben”, it continue increased at early stage, during 6～7 weeks its change was not evidently and retained at 11.0 mg/100 g·FW, even reduce more or less, but it rised at 17.7 mg/100 g·FW sharply. So we knowed that“hongxiangli”was a variety ofβ-Carotene accumulation.After pollination, glucose and fructose were the predominant soluble sugars detected in flesh of pumpkin before sucrose accumulation.“miben”and“huanglang”had no apparent differences in contents and had very similar accumulating patterns. The accumulation of sucrose occurred in mid-stages and latter-stages of fruit development. The genotype with high sucrose“miben”pumpkin accumulation had much intensive and faster sucrose accumulation with much higher sucrose content at maturity.“hongxiangli”had much intensive and faster starch accumulation, and was superior in starch accumulation.In early stage of fruit development, the sucrose cleavage enzymes behaved much higher activities than sucrose synthetic enzymes. The net activities between synthesis and cleavage had higher negative value. The photosynthetic substances translocated were decomposed, consumed and utilized, and the rate for sucrose accumulation was slower. In late developmental stage, the sucrose was quickly accumulated as a result of the sucrose cleavage enzymes behaved lower activities than sucrose synthetic enzymes at this stage, and they got balance till mature. In the present investigation, there was no or synthesis very low sucrose accumulation when the net activities was negative. After net activities was changed to positive, sucrose accumulation was enhanced.Sucrose accumulation coincided with the sucrose phosphate synthase activity and sucrose synthase activity in“hongxiangli”pumpkin. Sucrose accumulation increased with the hoist of sucrose phosphate synthase activity and sucrose synthase. There was higher invertase activities in early developing fruits in“miben”and“huanglang”, which gave rise to higher hexose contents in flesh. Hexose was the carbon source for vigorous growing tissues. Moreover, high hexose level was essential to maintain high osmotic pressure in cell and ensure sufficient water imbibition in early stage. At mid-stages, sucrose accumulation coincided with the hoist of sucrose phosphate synthase activity and sucrose synthase activity in“huanglang”and“miben”pumpkin. A reduction in acid invertase, would be a prerequisite for sucrose accumulation at latter-stages.The genotype with high starch“hongxiangli”accumulation had no relationship with starch phosphorylase, and coincided with the sucrose synthase activity.“miben”starch accumulation had the similar starch-accumulating patterns with“hongxiangli”at early stage. In latter developmental stage of“huanglang”, the starch was quickly accumulated as a result of the hoist of starch phosphorylase at this stage.According to our study, we thought that the sucrose accumulation in fruit due to both the high sucrose phosphate synthase and sucrose synthase activity and low invertase activity. Sucrose synthase acted an important role at starch accumulation in high-starch accumulation fruit, starch phosphorylase caused starch accumulation in low-starch accumulation fruit.更多还原