哈密瓜果实在发育和成熟期中的呼吸代谢变化

哈密瓜果实的发育及贮藏性能与呼吸有关。国内外对哈密瓜的呼吸途径研究很少。为此我们对哈密瓜果实在发育和成熟期中的呼吸代谢变化进行了研究。     

草莓果实成熟期间RNA代谢的变化

现已证明,鳄梨和番茄等跃变型果实的成熟涉及基因表达的改变和新蛋白质(酶)的合成(Brady 1987)。但是,关于草莓这类非跃变型果实成熟的生化控制机理却很少报道,它们是否也如同跃变型果实那样与新的核酸和蛋白质合成有关?本实验测定了草莓果实成熟期间poly(A)+RNA含量的变化和poly(A)+RNA的体外翻译活性,目的在于探讨草莓果实的成熟机     

草莓果实发育成熟过程中糖苷酶和纤维素酶活性及细胞壁组成变化

以丰香和红丰草莓为试材,对果实发育成熟过程中细胞壁水解酶活性和细胞壁成份变化进行了研究．结果表明：半乳糖苷酶和α-甘露糖苷酶活性随草莓果实成熟而提高,葡萄糖苷酶活性不随草莓果实成熟而提高．随着果实发育成熟,纤维素酶活性、果胶酶活性不断提高．果实中未检测到内切多聚半乳糖醛酸酶活性,外切多聚半乳糖醛酸酶活性变化不随果实成熟软化而提高．随果实发育成熟,细胞壁中可溶性果胶和半纤维素增加,而离子结合果胶和共价结合果胶及纤维素减少．     

嫁接的西瓜果实发育过程中叶和果实蔗糖代谢的一些特性

嫁接瓜果实发育过程中,叶内蔗糖含量和干物质积累显著高于自根瓜,自根瓜和嫁接瓜的叶中蔗糖含量与酸性转化酶（AI）、蔗糖磷酸合酶（SPS）活性均呈显著正相关;嫁接瓜果实中蔗糖含量显著低于自根瓜,SPS活性和果实中糖分的跨液泡膜运输能力亦较自根瓜低;自根瓜和嫁接瓜叶的干物质积累与叶中AI和SPS活性、果实AI活性呈显著负相关,与液泡膜H^＋-ATPase活性呈显著正相关。     

ARF和Aux/IAA调控果实发育成熟机制研究进展

生长素是调控果实发育成熟的重要植物激素之一。在生长素介导的信号转导机制中,ARF和Aux/IAA扮演重要的角色。ARF与生长素响应基因启动子区域内的生长素响应元件结合,促进或抑制基因的表达。Aux/IAA通过结构域Ⅲ和Ⅳ与ARF特异性结合,从而调节生长素早期应答基因的转录功能。研究表明,ARF因子参与调控果实形态发育、硬度和糖分积累等,Aux/IAA因子在授粉、果实形态发育等方面作用明显。此外ARF和Aux/IAA之间相互或与自身发生的互作以调控下游基因表达是植物体响应生长素信号的主要机制。介绍了ARF和Aux/IAA的结构特征、在不同植物中的分布状况以及与果实发育成熟的关系,同时讨论了ARF和Aux/IAA互作的研究现状,旨为进一步阐明生长素调控果实发育成熟的机制提供参考。     

乙烯释放和呼吸强度的变化与甜瓜果实贮藏期间成熟与衰老的关系

不同品种的甜瓜采收后和贮藏过程中乙烯释放和呼吸强度可分为三种类型:1.乙烯释放和呼吸均有跃变;2.呼吸下降而乙烯释放有跃变;3.乙烯释放和呼吸均平缓。第三种类型的贮藏质量较好。随着果实的成熟和贮藏时间的加长,果腔内 CO_2分压增加,O_2分压下降。     

植物果实发育成熟相关转录因子的研究进展

转录因子是调控植物生长、发育及衰老的一类重要的蛋白质,它们调控机制的阐明是应用于现代农业技术的潜在工具。本研究针对与植物果实发育成熟密切相关的AP2/EREBP、SBP-box、EIN3/EILs的转录因子的研究进展进行了综述。     

杨梅果实发育进程中的碳水化合物代谢

以‘乌紫’和‘荸荠’两个杨梅品种为试材,测定了干鲜重、糖含量、可滴定酸含量、蔗糖和己糖代谢相关酶活性的动态变化。结果表明,杨梅果实的干鲜重、含糖量的快速增长和可滴定酸含量的快速下降均发生在果实发育后期。成熟‘乌紫’杨梅果实的蔗糖含量约占总糖的2／3以上,而‘荸荠’杨梅仅为总糖的49％。‘荸荠’杨梅的转化酶和蔗糖合酶分解活性随着果实发育呈上升趋势,‘乌紫’杨梅的则变化不大。两个品种的蔗糖磷酸合酶活性随着果实发育呈上升趋势,但蔗糖合酶合成活性到果实发育中期后下降。两个品种的己糖激酶活性变化相似,但果糖激酶活性的变化趋势不同。     

Studies on the Active Changes of GA3 and Cytokinins During Development and Ripening in Seabuckthorn Fruits

The phenological stages in seabuckthorn (Hippophae rhamnoides L. Subsp. sinensis Rousi and H. thibetana Schlechted) distributed naturally over an area of Wushao ridge were observed. The changes in levels of endogenous phytohormones GA3, iPA, zeatin, IAA and ABA were investigated systematically during development and ripening periods in the two sorts of fruits. The results showed that two peak values of GA3 level in seeds were detected (in 105—109 days and 128--132 days after anthesis). The first peak value of isopentenyl adenine (IPA) in seeds was determined in 92--96 days when the fruit was starting to change its colour and just right now the zeatin first appeared. The iPA content reached the second peak value in 127-136 days after anthesis during fruit full ripening and beginning to deciduous leaf and the maximum of zeatin in seeds appeared near the same time (in 127 days after anthesis). It was remarkable that the zeatin content in fruit stalk and flesh still was kept on high level, in the meantime the zeatin level in seeds dropped down rapidly. Based on the facts that the time of the first peak value in GA3 and iPA level is close to the date when ABA is first detected, and the date of second peak value in GA3, iPA and IAA is coincident with the time of maximum in ABA and zeatin levels make it reasonable to consider that the balance of phytohormones may be more important than absolute amounts of any single hormone during the periods of fruit development and ripening, and meanwhile it also proved that GA3 and CTK play an important regulatory role in controlling fruit ripening and colour changing process of seabuckthorn fruit.     

番茄果实成熟过程中钙调素含量变化及其与乙烯生成的关系

应用酶联免疫吸附法(ELISA)测定番茄(Lycopersicon esculentum Mill大红品种)果实成熟过程中钙调素(CaM)含量的变化。果实开始成熟(发白期),CaM含量随着呼吸跃变上升,成熟时(粉红期)达到最大,过熟衰老时则下降。果实内部乙烯浓度、ACC含量及其合成酶活性也随跃变而增加,随过熟衰老而降低。GaM含量在果实不同部位中的分布有明显差异,跃变上升期以子房腔组织含量最高,并由中心向外逐渐降低,外周果皮含量最低。此时用外源乙烯催熟处理促进各部位CaM增加。成熟衰老时子房腔组织首先衰老,CaM含量大为降低,但在中柱和果皮中却高于跃变上升期。外源乙烯促进衰老使CaM下降。Ca~(2+)促进番茄圆片CaM含量增高和乙烯产生,CaM抑制剂CPZ,TFP在降低CaM含量的同时也抑制乙烯的产生。     

Regulatory Mechanisms of Textural Changes in Ripening Fruits

Texture changes in ripening fruits influence consumer preference, fruit storability, transportability, shelf-life, and response to pathogen attack. Genetic regulatory factors as well as environmental conditions simultaneously affect texture changes in ripening fruit. Recent physiological and molecular studies provide insights into our knowledge and understanding of events and/or factors that contribute to changes in fruit texture, including softening and lignification. The roles of enzymes involved in modification and/or regulation of cell wall components as well as ethylene signaling components that play key roles in fruit textural changes during fruit ripening and storage will be presented and discussed. In addition, physical as well as chemical regulation of textural changes in ripening fruit will be explored.     

Carotenoid Pigment Changes in Ripening Momordica charantia Fruits

The carotenoid composition of Momordica charantia fruit (pericarp)at four levels of maturity was extensively investigated. Thenumber of carotenoids isolated increased from five in the immaturefruit to six at the mature-green and 14 at the partly-ripe andripe stages. Cryptoxanthin, which could not be isolated at theimmature and mature stages, accumulated rapidly at the onsetof ripening to become the principal pigment of the ripe fruit.Moderate increases were seen in ß-carotene, zeaxanthinand lycopene concentrations as ripening progressed. The reversetrend was observed with lutein and -carotene which were themajor pigments of the immature fruit. Prior to the colour break,only the hydroxy derivatives of -carotene (zeinoxanthin andlutein) could be detected; the ß-hydroxy compounds(cryptoxanthin and zeaxanthin) appeared and predominated thereafter.The hydroxy carotenoids of the ripe fruit were almost entirelyesterified in contrast to those of the unripe fruit which weremainly unesterified. Traces of flavochrome, 5, 6-monoepoxy-ß-carotene,mutatochrome, -carotene, -carotene, -carotene and rubixanthinwere detected in the partly-ripe and ripe fruits but not inthe immature and mature-green samples. Phytofluene was observedin trace levels at all stages.     

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.     

番茄果实中焦磷酸：D－果糖－6－磷酸1－磷酸转移酶的结构和动力学特性

比较了番茄绿果实和红果实中焦磷酸－Ｄ－果糖－６－磷酸１－磷酸转移酶的两种酶型（Ｑ１和Ｑ２）的结构和动力学特性。绿果实中大分子酶型Ｑ２（绿Ｑ２）在酶蛋白量和酶活力方面均占绝对优势,而在红果实中小分子酶型Ｑ１（红Ｑ１）起主导作用。ＳＤＳ－ＰＡＧＥ凝胶扫描结果显示绿Ｑ２和红Ｑ２（红果实中大分子酶型）的亚基组成不同。组成该酶的α－基（６６ｋＤ）和β－亚基（６０ｋＤ）的化学裂解肽谱表明两亚基差异很大,同时证明构成Ｑ１和Ｑ２的β亚基具有相同的肽谱。分析Ｑ１和Ｑ２的圆二色性（ＣＤ）光谱表明绿Ｑ２和红Ｑ２均主要由α－螺旋和β－折叠构成二级结构,几乎没有无规卷曲。动力学分析表明激活剂果糖－２．６－二磷酸不同程度地影响Ｑ１和Ｑ２对正反应底物的亲和力,而对逆反应活性无明显影响。绿Ｑ２的正反应和逆反应最大活力比值低于绿Ｑ１,红果实中则反之。     

Studies on Water Movement Into and Out of Grapevine Fruits During the Ripening

The experiment was carried out during the ripening of grape (Vitis vinifera L. and V. vinifera × V. labrusca) fruits using the technique of dye tracing and measurement of water potential. Under the natural conditions of sufficient soil water supply and those of a high evapotranspiration potentiality on clear days, the water in fruits was transfered, during the morning and afternoon, out of the clusters and into the xylem of shoots; but the fruits capture water in the late afternoon and evening from the xylem of shoots. The diurnal variations of the water exchange between fruits and the xylem of shoots have been described and these variations seemed to be relevant not only to the differences of water potential between leaves and fruits but also to the hydraulic status of fruits. Under the mild water stress, the variations of the diurnal "fruits-shoots" water exchange were similar to those under the conditions of ample water supply, but the rate of "fruits-shoots" water exchange in the lightly stressed vine was decreased as compared with the fully watered vines. After a certain period of severe water stress, the fruits possessed a great capacity of conserving their water and an equilibrium in water potential was set up between leaves and fruits so that the fruits did not lose any more water. Under a sudden severe water stress, the fruits lost water at a higher outflux rate than when the water supply was sufficient. However, this water loss ceased rapidly. The water flowing out from the fruits was privileged to pass in the lateral shoots located above and on the same side of the fruits, and then the water might enter the primary shoot leaves situated above and on the same side of the fruits. Water captured by the fruits of the well watered vines in the evening came from the roots while under severe stress water might be obtained from the roots and also from the leaves as well. The fruit cell water potential, solute potential and pressure potential were different from those of leaves, mainly in the more important differences of water potential necessitated for the volume changes of fruit cell after incipient plasmolysis in com parison with leaves. Finally the relationships between water exchange and water potential dif ferences between "fruits-shoots", associated with the fruits hydraulic status, have been discussed. The possible relationships between water "sink-source" of fruits and the fruit development have been analysed.     

Changes in Cell Wall Polysaccharides During Fruit Ripening

Received 20 June 2000/ Accepted in revised form 20 July 2000     

Alternative Respiration and Heat Production in Ripening Banana Fruits (Musa paradisiaca van Mysore Kadali)

The involvement of alternative respiration in thermogenesisduring the ripening of banana {Musa paradisiaca var. MysoreKadali) fruits, attached to a bunch, has been examined. Thetemperature of the youngest (unripened) banana fruit increasedfrom 27·0 ± 0·2°C to 30·8±0·1°C and the total respiration (in nmo1 oxygen min¹ g¹ drywt.) increased from 1·39·6 ± 5·5to 167·3 ± 7·0 at the fully ripened stage.Although the capacity for alternative respiration showed littlechange, the actual operation of this pathway increased from38 to 73% (p= 0·38 to 0·73) during ripening. Similarresults were obtained in fruits along the central axis at differentstages of ripening. It is suggested that alternative respirationmay contribute to the temperature rise observed in ripeningbanana fruit. Key words: Alternative respiration, tehrmogenesis, fruit ripening