香蕉果实成熟软化过程中细胞壁物质的变化

系统研究了香蕉果实软化过程中细胞壁物质―醇不溶性固形物(AIS)以及3种不同性质的果胶物质:水溶性果胶(WSP)、酸溶性果胶(HP)和碱溶性果胶(OHP)含量的变化。结果表明:随果实的成熟软化,AIS的含量不断降低,且在呼吸跃变时急剧降低;WSP的含量不断增加,HP和OHP的含量不断减少,且均表现出在早期变化量少,在果实硬度迅速降低时变化明显。该研究进一步证明细胞壁物质的变化是导致香蕉果实软化的主要原因。     

采后钙处理对梨果实钙的形态和果胶及相关代谢酶类影响的研究

研究了黄花梨经浸钙处理后,果实钙形态转变及果胶含量、多聚半乳糖醛酸酶（PG）和果胶甲酯酶（PME）活力的变化,以及果实硬度的变化。结果表明：浸钙处理的果实总钙含量显著提高,其硬度明显高于对照,且有利于细胞膜透性的保持;梨果实中的NaCl溶性钙最多,其次是水溶性钙,醋酸溶性钙和HCl溶性钙含量较少。在果实贮藏21d时,水溶性钙含量有一个上升的过程,而NaCl溶性钙则有一个下降的过程。浸钙处理后,除醋酸溶性钙外,果实中的水、NaCl和HCl溶性钙含量均有显著的提高。浸钙处理明显抑制了果胶的降解进程与PG的活力,但对PME抑制作用不明显。浸钙处理能提高果实硬度可能与浸钙处理抑制了PG活力有关。     

花期减少施钙量对不同钙效率番茄果实钙形态和含量的影响

花期降低施钙量后,钙低效番茄品种L-402果实中钙含量显著降低,高效品种江蔬一号降低不显著,镁含量显著增加,钾含量有增加趋势。果实底端的钙含量高于顶端,降低施钙量后果实水溶性钙含量和比例显著提高,果胶酸钙含量和比例降低,磷酸钙含量也降低。钙低效品种L-402水溶性钙含量的增加,以及果胶酸钙和磷酸钙的降低程度,都大于高效品种江蔬一号,且降钙后果实顶端的革酸钙含量和比例增加。     

钙对香蕉采后乙烯释放的抑制

本实验用CaCl_2溶液对香蕉(Musa acuminata cf. 'Dwarf Davendish')组织进行真空浸透处理,研究Ca~(2 )对香蕉采后乙烯释放、EFE活性、ACC水平以及ACC/MACC比值的影响。结果表明,Ca~(2 )处理可抑制香蕉果皮和果肉组织乙烯生成,对抑制果皮的乙烯生成尤为明显。Ca~(2 )处理还可降低内源ACC水平,抑制EFE活性。结果还显示,Ca~(2 )处理对组织中ACC/MACC比值有一定影响。     

钙渗入抑制翠冠梨果实衰老软化作用的生理生化机制

以翠冠梨为试材,研究了采后浸钙对翠冠梨果实贮藏性的影响。结果表明：(1)钙处理可明显降低果实腐烂率,增加果实中钙的含量;(2)翠冠梨采后衰老时,硬度下降,膜脂过氧化物丙二醛含量增多,质膜透性增大,果实硬度与丙二醛含量呈负相关,钙处理可抑制果实的膜脂过氧化作用,降低质膜透性、呼吸强度、乙烯释放速率,延长了翠冠梨货架寿命。其中采后浸10％CaCl2处理延缓果实衰老软化效果最好。     

水杨酸对冷藏板栗贮藏效果的影响

以不同浓度水杨酸、不同浸果时间研究水杨酸对板栗果实冷藏效果的影响。结果表明:水杨酸可抑制贮藏期间栗果呼吸强度,推迟呼吸跃变的到来;还可抑制VC含量和淀粉含量;水杨酸处理后栗果腐烂率和质量损失率均降低。最佳处理方式为0.5 g/L水杨酸浸果10 m in。     

ABA和腐胺处理减轻香蕉果实贮藏冷害

研究了脱落酸(ABA) 200 μmol/L和腐胺(Put) 5 mmol/L处理对贮藏于8℃的香蕉果实耐冷性的影响.两种处理均能使香蕉果实冷害症状延迟3～4 d出现,降低细胞膜透性和MDA含量,提高果皮SOD和POD活性.用高效液相色谱仪测定果实ABA和多胺含量的结果表明,ABA和Put处理均提高了果实ABA含量.其中前者处理的果实ABA含量较高,Put处理的果实多胺(Put、Spd、Spm)含量明显增加,而ABA处理不能提高多胺含量.     

香蕉ASR的特征和采后表达分析

从香蕉cDNA文库中获得香蕉ASR全长cDNA序列,命名为MaASR。构建遗传进化树发现MaASR与单子叶植物中的芭蕉科植物的亲缘关系较近。对正常成熟和乙烯处理的香蕉果实各时期内源ABA的含量进行测定,结果表明,在正常成熟的香蕉果实中,成熟早期(0-2 d),内源ABA含量相对较低,第8天ABA含量达到最大,随后迅速下降。在乙烯处理的香蕉果实中,ABA含量急剧上升,第3天ABA含量达到高峰,随后逐渐下降。利用荧光定量RT-PCR对MaASR在正常成熟和乙烯处理后的果实中的表达情况进行分析,在自然成熟的果实中,MaASR在采后2 d达到高峰,而后迅速下降,在6-16 d时一直保持较低水平。在经外源乙烯诱导的果实中,MaASR表达水平没有表现出剧烈变化的趋势,整体表达量较低。表明MaASR对乙烯信号有应答,但应答强度较低,其表达趋势与ABA的含量或者信号强度呈负相关。     

膨大期果面喷施IAA对桃成熟期果实性状和相关基因表达的影响北大核心CSCD

为明确桃果实发育后期外源生长素对果实成熟的影响及更深入的认识生长素调控果实发育与成熟的机制,本研究以桃品种‘小白凤’为试材,采用不同浓度的外源IAA(200,10,0.1μmol/L)喷施第2次快速膨大期的桃果实,在处理后10,20,30 d分别取样,分析桃果实的硬度,糖组分(蔗糖、葡萄糖、果糖、山梨醇),果胶,纤维素含量以及乙烯释放量的变化,并对200μmol/LIAA处理后30 d及对照组的果实进行了转录组测序分析,深入认识生长素调控桃果实成熟的作用和机理。结果表明,(1)IAA处理后30 d时,200μmol/L处理组桃果实果肉硬度与对照组相比显著增加,成熟期平均延迟5 d,而10,0.1μmol/LIAA处理组与同期对照组间无显著差异。(2)果肉蔗糖含量在0.1,200μmol/LIAA处理后30 d显著低于同期对照组,在10μmol/LIAA处理后30 d时与对照组无显著差异;葡萄糖、果糖和山梨醇含量在各浓度IAA处理后30 d时多与对照组间无明显差异。(3)在处理30 d时,果肉中可溶性果胶含量在0.1μmol/L IAA处理组与对照组无显著差异,在10,200μmol/LIAA处理组均显著低于对照组,此时不同浓度IAA处理桃果肉中不可溶果胶和纤维素含量均与对照组之间无显著差异。(4)在IAA处理后10,20,30 d时,果实乙烯释放量均表现为0.1,10μmol/L处理与对照组无显著差异,200μmol/L处理组显著低于对照组。(5)转录组数据显示,200μmol/L IAA处理与对照组中共存在86个差异表达基因,KEGG分析发现其中有6个与果实发育成熟密切相关的代谢途径中多个基因的表达谱发生显著变化,且变化趋势与已测定的生理指标数据吻合。综合分析表明200μmol/L的外源IAA处理第2次快速膨大期的桃果实能够延缓果实成熟的进程。     

香蕉果实软化相关β-半乳糖苷酶基因的克隆及其表达分析

β-半乳糖苷酶（β-galactosidase）通过分解细胞壁半纤维素切除半乳糖键而参与果实软化。为了阐明香蕉（Musasp．）果实成熟过程中的软化与细胞壁代谢酶β-半乳糖苷酶基因表达之间的关系,采用RT-PCR方法,从成熟香蕉果实果肉中分离了编码β-半乳糖苷酶基因的部分cDNA（MA-Gal）,序列分析表明,MA-Gal包含927bp,编码309个氨基酸,包含5个β-半乳糖苷酶结构域（典型真核生物中β-半乳糖苷酶包含7个结构域）,推导的MA-Gal蛋白质中有β-半乳糖苷酶蛋白的催化活性部位GGPIILSQIENEY（F）;系统进化树分析结果表明MA-Gal属于第一类β-半乳糖苷酶基因（该类主要在果实中表达）;β-半乳糖苷酶活性和硬度的变化表明其与香蕉果实硬度变化密切相关;Northern分析显示,跃变前期的果肉中,MA-Gal基因的表达量很低,后随着果实的软化表达量不断增加,并在呼吸跃变后达到最高。所有结果表明,MA-Gal参与香蕉果实成熟过程中的软化。     

Respiratory Contribution of the Alternate Path during Various Stages of Ripening in Avocado and Banana Fruits

The respiration of fresh slices of preclimacteric avocado (Persea americana Mill. var. Hass) and banana (Musa cavendishii var. Valery) fruits is stimulated by cyanide and antimycin. The respiration is sensitive to m-chlorobenzhydroxamic acid in the presence of cyanide but much less so in the presence of antimycin. In the absence of cyanide the contribution of the cyanide-resistant pathway to the coupled preclimacteric respiration is zero. In uncoupled slices, by contrast, the alternate path is engaged and utilized fully in avocado, and extensively in banana. Midclimacteric and peak climacteric slices are also cyanide-resistant and, in the presence of cyanide, sensitive to m-chlorobenzhydroxamic acid. In the absence of uncoupler there is no contribution by the alternate path in either tissue. In uncoupled midclimacteric avocado slices the alternate path is fully engaged. Midclimacteric banana slices, however, do not respond to uncouplers, and the alternate path is not engaged. Avocado and banana slices at the climacteric peak neither respond to uncouplers nor utilize the alternate path in the presence or absence of uncoupler.

The maximal capacities of the cytochrome and alternate paths, V_cyt and V_alt, respectively, have been estimated in slices from preclimacteric and climacteric avocado fruit and found to remain unchanged. The total respiratory capacity in preclimacteric and climacteric slices exceeds the respiratory rise which attends fruit ripening. In banana V_alt decreases slightly with ripening.

The aging of thin preclimacteric avocado slices in moist air results in ripening with an accompanying climacteric rise. In this case the alternate path is fully engaged at the climacteric peak, and the respiration represents the total potential respiratory capacity present in preclimacteric tissue. The respiratory climacteric in intact avocado and banana fruits is cytochrome path-mediated, whereas the respiratory climacteric of ripened thin avocado slices comprises the alternate as well as the cytochrome path. The ripening of intact fruits is seemingly independent of the nature of the electron transport path.

Uncouplers are thought to stimulate glycolysis to the point where the glycolytic flux exceeds the oxidative capacity of the cytochrome path, with the result that the alternate path is engaged.

     

Effect of phytohormones on pectate lyase activity in ripening Musa acuminata.

A differential activity peak of pectate lyase (PEL) was observed during ripening of banana fruits (Musa acuminata Harichhal) receiving different hormone treatments. Exposure of fruits to 25 ppm ethylene for 24 h, as well as dipping of M. acuminata fruits in 1 mM 2,4-dichlorophenoxy acetic acid (2,4-D) for 4 h, hastened fruit ripening. Both PEL activity peak and climacteric peak were observed on the 4th and 10th days of treatment with ethylene and 2,4-D, respectively, compared to the 16th day in control fruits. Gibberellic acid (GA) treatment retarded fruit ripening and both PEL activity and climacteric peaks were observed on the 19th day. Treatment of fruits with ethylene or 2,4-D also advanced the appearance of a polygalacturonase (PG) peak and GA delayed its appearance, but the activity peaks always appeared in post-climacteric fruits, in contrast to PEL activity peaks coinciding with the respiratory peaks.     

Effects of Oxygen Concentration and Ethephon upon the Respiration and Ripening of Banana Fruits

A respiratory climacteric and accumulation of soluble solidsof pulp were induced in banana fruits by (2-chlorethyl) phosphonicacid (ethephon) at oxygen concentrations of 3–21% (v/v).However, induction of peel colour change by ethephon was retardedor prevented at oxygen concentrations of 10% (v/v) or less.Thus pulp tissue ripened whilst the peel remained green. Respirationrate, soluble solids content of pulp, and peel colour were notaffected by ethephon at oxygen concentrations of 1% (v/v) orless. The kinetics of respiratory response to ethephon are consistentwith a model in which ethylene (derived from ethephon) is acoupling-activator of respiration. In this model ethylene decreasesthe affinity of an enzyme system for its substrate, but acceleratesthe release of product.     

钙对中华猕猴桃果实采后乙烯释放和呼吸的影响

不同浓度(0.2 mol/L、0.5 mol/L 0.8 mol/L) CaCl₂溶液真空渗透处理对中华猕猴桃果实采后乙烯释放都有明显的抑制作用,其中0.5 mol/L Ca²⁺处理尤为显著,采后5天果实仍保持极低水平的内源乙烯,乙烯峰也延迟2~4天出现。不同品种间没有明显差异。试验结果还表明,Ca²⁺处理对果实采后呼吸不存在明显的抑制作用,但不同品种间有一定差异。     

Cyanide-Resistant Respiration in Relation to Fruit Respiratory Climacteric

Changes in respiratory rate and the effects of respiratory inhibitorson respiration were determined in apple (Malus sylvestris cv. Delicious) and red pepper (Capsicum fructescens) fruits dusting different stages of development and ripening.The results showed that there was an abrupt rise in respiration daring ripening inapple fruit, but the respiration of the red pepper declined continuously throughout theripening period. Thus the apple is climacteric and the red pepper is non-climacteric fruit. The respiration of apple fruit was sensitive to KCN (1 mM) during the period ofdevelopment but changed to CLAM-sensitive and CN-resistant during preclimactericand climacteric phases, indicating that a diversion of respiratory pathways from the cy-tochrome path to the alternative path has occurred. The respiration of the red pepperfruit was CN-sensitive thoughout the whole period of fruit ripening, suggesting thatthe operation of the CN-resistant path was insignificant. Slices from climacteric apple fruits developed induced .respiration after aging, bothKCN and CLAM (1 mM) inhibited the induced respiratic considerably. However, slices from red pepper fruits showed no evidence of induced respiration after aging. Slices from climacteric apple fruits infiltrated with 3 mM CLAM before aging, reducedthe peak of the induced respiration by about 30%, indicating that the development ofinduced respiration was suppressed by the presence of CLAM. The above results indicated that the: climacteric fruits were characterized by diversion of traffic from the cytochrome path to the alternative path during ripening andby the development of induced respiration after slicing and aging. While in nonclimacteric fruits no .diversion of electron transport path was observed during ripening andno induced respiration occurred after aging. Although both the eytochrome and alternative pathways were present in the tissue of red pepper fruits, the alternative pathwas not operating except when the cytochrome path was blocked or was saturated by electron flow.     

The Relation of Ethylene Production and Respiration with Maturation and Senescence of Melon during Postharvest-Storage

There are three types of ethylene production and respiration during the postharvest storage of melon fruits: 1. with climacteric rise in both respiration and ethylene production; 2 with climacteric rise in ethylene production but respiration declined gradually; 3 with no appreciable change in both respiration and ethylene production. The last one has good storage quality.     

Comparison of Propylene-induced Responses of Immature Fruit of Normal and rin Mutant Tomatoes

Continuous application of propylene to 40 to 80% mature fruits of normal tomato strains (Lycopersicon esculentum Mill.) advanced ripening in fruits of all ages by at least 50%. Although preclimacteric respiration was stimulated by propylene treatment, there was no concomitant increase in ethylene production. Once ripening commenced, the rates of endogenous ethylene production were similar in both propylene-treated and untreated fruits. Continuous exposure to propylene also stimulated respiration in immature fruits of rin, a nonripening mutant. Although respiration reached rates similar to those during the climacteric of comparable normal fruits there was no change in endogenous ethylene production which remained at a low level. Internal ethylene concentrations in attached 45 to 75% mature fruits of rin and a normal strain were similar. It is suggested that the onset of ripening in normal tomato fruit is not controlled by endogenous ethylene, although increased ethylene production is probably an integral part of the ripening processes.