金丝小枣和冬枣果实发育过程中低聚糖和多糖含量的动态研究

对冬枣和金丝小枣的花和不同生育阶段果实中低聚糖和多糖的含量进行了动态测定。结果表明,低聚糖出现的时期和种类及多糖的单糖组成和含量变化趋势,在品种间存在差异。在2个品种的花和幼果中未检出低聚糖;金丝小枣在果实白熟期检测到大量的二糖(蔗糖)并随果实进一步成熟含量持续上升;冬枣则在白熟期前3周即可检测到大量的二糖,并随着枣果的成熟出现了三糖和四糖。多糖含量随枣果发育逐渐增加,其中金丝小枣的多糖在白熟期以前变化平稳,之后呈近直线上升趋势;冬枣的多糖则在整个枣果生育期中一直呈缓慢上升趋势。组成多糖的单糖种类和含量也均随枣果发育呈递增趋势,在枣果半红期以前只检测出果糖、葡萄糖和半乳糖,其中以果糖含量最高;半红期后又检测出了甘露糖、鼠李糖和阿拉伯糖,但含量很低。     

Variations in contents of (−)-epicatechin and activities of phenylalanine ammonialyase and polyphenol oxidase of longan fruit during development

Longan fruit has attracted much attention by consumers over the world due to the unique sweet–sour taste. However, the fruit brown rapidly at ambient temperature during storage, due to enzyme-catalyzed reaction of phenolics. Experiments were conducted to understand the variations in the levels of total phenolics and (−)-epicatechin as a major substrate for polyphenol oxidase (PPO) in pericarp tissue of longan fruit during development. The activities of phenylalanine ammonialyase (PAL) and PPO, involved in the synthesis and oxidation of (−)-epicatechin, respectively, during longan fruit development were also measured. During fruit development, the content of total phenolics decreased rapidly and then increased while the content of (−)-epicatechin tended to decrease. Both PAL and PPO activities decreased rapidly at the early fruit development and increased later but the increase of the former appeared was 10 days earlier than the latter. Thus, the level of (−)-epicatechin depended largely on PAL activity but it could involve the conversion of (−)-epicatechin into other flavonoids. This study could help develop appropriate preharvest treatments to control pericarp browning of harvested longan fruit by understanding the variation in the level of the major browning substrate during development.     

甜樱桃果实发育过程中细胞壁组分及其降解酶活性的变化

【目的】了解甜樱桃在果实发育过程中质地变化与果实细胞壁组分及其降解酶活性的关系。【方法】以硬肉型品种‘美早’、常规型品种‘红灯’和软肉型品种‘佳红’为试材,分别在硬核期、转白期、着色期和成熟期对果实硬度、细胞壁组分以及细胞壁降解酶活性进行了测定分析。【结果】‘美早’硬度降低速率较慢,成熟期硬度高于其他2个品种,WSP升高速率、纤维素降解速率低,PME、α-L-Af、Cx、β-Gal活性低。‘红灯’硬度降低速率较快,在果实发育后期硬度低于‘美早’,WSP升高速率与纤维素降解速率高,PME、α-L-Af活性高。‘佳红’在转白期硬度迅速降低且后期质地软,它的纤维素降解速率高,PME、α-L-Af、Cx、β-Gal在转白期之后活性较高。【结论】甜樱桃果实成熟过程中,原果胶的降解和纤维素的水解是果实软化的关键因素。果实细胞壁组分降解是多种酶协同作用的结果。PME和α-L-Af与‘红灯’和‘佳红’硬度显著负相关,并且活性在‘美早’中显著低于其他2个品种,这可能是果实硬度较高的主要原因。纤维素和原果胶降解速率低,PG活性高和β-Gal活性低可能是导致硬度高的次要原因。Cx酶活由于在‘红灯’中并没有显著影响到到果实硬度,而在‘佳红’和‘美早’中产生了不同的影响,可能是品种间的差别。     

套袋对红地球葡萄果实发育过程中糖代谢及转化酶活性的影响

以红地球葡萄为试材,研究套袋对葡萄果实中糖代谢及转化酶活性的影响。结果表明:套袋果实在发育过程中蔗糖、葡萄糖、果糖含量和转化酶活性变化趋势与对照基本一致。果实成熟后套袋果的可溶性总糖含量明显高于对照。在果实发育前期,套袋明显提高了果实中蔗糖的相对含量及酸性转化酶活性。套袋可能主要是通过影响果实发育早期转化酶活性来影响果实糖分积累。     

甜樱桃红灯果实发育过程中果肉及种子内源激素含量变化动态

以9a生红灯甜樱桃(Prunus avium L.)为试材,对其果实不同发育时期果肉及种子中内源激素含量的变化动态进行了测定分析,结果表明,甜樱桃果肉及种子中内源激素含量与其果实的生长发育有密切关系。果实发育第Ⅰ速长期(盛花后5～15d),果肉中生长促进型激素(ZRS、IAA和GAS)含量均较高,进入硬核期(盛花后15～25d)均呈下降趋势,其中IAA和GAS均降到最低值,随果实的第Ⅱ次速长果肉中ZRS、IAA和GAS含量均迅速增加且分别出现最大值;与之相反,种子中ZRS、IAA和GAS含量在第Ⅰ、Ⅱ速长期较低,在硬核期含量最高,这与甜樱桃果实及种子的生长规律相吻合。果肉中ABA含量分别在盛花后5、15和35d出现高峰,与甜樱桃的落果(花)时期基本一致。     

菠萝果实发育过程中有机酸含量及相关代谢酶活性的变化

以菠萝品种卡因为试验材料,测定了不同发育时期果实中有机酸含量及其有机酸代谢相关酶—磷酸烯醇式丙酮酸羧化酶(PEPC)、柠檬酸合成酶(CS)的活性变化,并对果实中酸积累与酶活性的关系进行了分析。结果表明,卡因菠萝果实中所含有机酸有柠檬酸、苹果酸、酒石酸、乙酸、草酸、马来酸,其中主要有机酸为柠檬酸(约占62%)、其次为苹果酸(约占14%)、酒石酸、乙酸和草酸的含量较低,马来酸微量。随着果实的发育,柠檬酸含量呈低-高-低的变化趋势,苹果酸、草酸、乙酸、酒石酸含量均呈下降趋势,柠檬酸在果实成熟时占主要优势,是果实主要的有机酸。在幼果期到果实迅速生长后期(花后10～70d),柠檬酸合成酶(CS)和磷酸烯醇式丙酮酸羧化酶(PEPC)活性与柠檬酸含量呈显著正相关。进入果实青熟期(花后90d)后,果实柠檬酸含量变化与PEPC和CS活性并无明显联系,此期酸积累不仅仅依赖这些酶的活性水平,还与其他因素有关。     

Changes in carbohydrate levels and their metabolic enzymes in leaves,phloem sap and mesocarp during cucumber (Cucumis sativus L.) fruit development

Levels of carbohydrates and activities of metabolic enzymes were examined in leaves (source), phloem sap (flow) and mesocarp tissues (sink) in the course of cucumber (Cucumis sativus L.) fruit development, from 2 days before anthesis to 20 days after anthesis. While total sugar levels increased in all the three sampling organs, starch levels declined in leaves and mesocarp tissues as fruit development progressed. Glucose and fructose were the primary contributors to the soluble sugar pools in mature leaves. Stachyose was found as the most important component of the phloem sap extracts, followed by sucrose and raffinose. However, the primary sugars accumulated in mesocarp tissues were glucose and fructose, not stachyose or sucrose. Activities of sucrose synthesizing enzymes (sucrose phosphate synthase plus sucrose synthase in the synthesizing direction) exceeded that of sucrose degrading enzymes (acid invertase, neutral invertase plus sucrose synthase in the degrading direction) in leaves, which might cause a sucrose pool utilized in raffinose and stachyose biosynthesis. While alkaline a-galactosidase form I activity declined, stachyose synthase activity showed a rapid increase until 12 days after anthesis and only subsequently decreased in leaves. Activities of sucrose degrading enzymes were always much higher than that of sucrose synthesizing enzymes in mesocarp tissues. Thus, sucrose accumulation could not occur in mesocarp tissues. While stachyose synthase activity steadily decreased, alkaline a-galactosidase form I activity showed a moderate increase before decrease in mesocarp tissues. The relationship between levels of soluble sugars and activities of relative enzymes was also discussed.     

Changes in enzymes involved in photosynthesis and other metabolic processes in the fruit of Opuntia ficus-indica during growth and ripening

The aim of this study was to investigate changes in the abundance of a number of enzymes in the peel, core and seeds of fruits of Opuntia ficus-indica (L.) Miller during development. The enzymes studied were phosphoenolpyruvate carboxylase (PEPC; EC: 4.1.1.31), ribulose-1,5-bisphosphate carboxylase/oxygenase (RUBISCO; EC: 4.1.1.39), aldolase (EC: 4.1.2.13), pyruvate, orthophosphate dikinase (PPDK; EC: 2.7.9.1), phosphoenolpyruvate carboxykinase (PEPCK; EC: 4.1.1.49) and aspartate aminotransferase (AspAT; EC: 2.6.1.1). To detect these enzymes, antibodies specific for each enzyme were used to probe Western blots of sodium dodecyl sulphate polyacrylamide gels. Fruit weight increased throughout development, and during ripening there was both an accumulation of total soluble solids and a decrease in both total titratable acidity and chlorophyll content. In the early stages of its growth the polypeptide pattern and enzyme composition of the fruit chlorenchyma was similar to that of the cladode. In the peel of the fruit PEPC, RUBISCO, plastidic aldolase and PPDK decreased to undetectable amounts as ripening progressed. PEPCK was not detected in either the chlorenchyma of the fruit or cladode. This showed that O. ficus-indica is not a PEPCK type CAM plant and that in this fruit PEPCK is not involved in the metabolism of organic acids. Cytosolic aldolase and AspAT were present in both the peel and core throughout development. The seeds accumulated storage proteins before the fruit ripened, and the abundance of all the enzymes studied declined once the accumulation of storage proteins was complete.