香蕉果实成熟软化时果皮和果肉中α-L-阿拉伯呋喃糖苷酶活性的变化

阿拉伯糖是果实软化过程中变化最明显的细胞壁糖残基之一,α-L-阿拉伯呋喃糖苷酶是导致细胞壁多糖中阿拉伯糖残基降解的主要糖苷酶。为阐明该酶在香蕉果实成熟软化中的作用,实验对香蕉贮藏过程中果皮和果肉中该酶活性以及果实硬度、呼吸强度和乙烯释放量的变化进行了研究。结果表明:α-L-阿拉伯呋喃糖苷酶在果实初期的变化很小,到果实硬度开始急剧下降时达到最大,增加量达10倍以上,且果肉中的酶活性大于果皮中;乙烯吸收剂处理延缓了香蕉果实呼吸和乙烯高峰的出现时间,降低了果实硬度、果皮和果肉中α-L-阿拉伯呋喃糖苷酶活性变化的速度和幅度。以上结果表明α-L-阿拉伯呋喃糖苷酶起诱导香蕉果实成熟的作用,在果实的软化中起着十分重要的作用,且其活性受乙烯的调节。     

The Development of the Banana Fruit

1. The banana fruit is either seeded or vegetatively parthenocarpic;the latter may or may not be seed fertile, depending on a complexof cytogenetical factors. Edible pulp (a starchy parenchyma),which fills the fruit in parthenocarpic types and surroundsthe seeds in seeded bananas, mostly originates from the outerlining of the loculus (the innermost layer of the pericarp). 2. The graphs of growth in volume of seeded banana fruits aresigmoid in shape. Those of parthenocarpic fruits are variablebut are not sigmoid and the shapes are related to specific origins. 3. Growth rates are related to certain ovule behaviours, toseed content of the fruit, and to ploidy. 4. -Naphthylacetic acid induces parthenocarpy in seeded bananasand stimulates it in weakly parthenocarpic types. By contrast,coumarin, a hormone inhibitor, inhibits it in strongly parthenocarpicforms. 5. Physiological and genetical implications of the results arediscussed. Fruit development is thought to be under hormonecontrol and two phases of development of the parthenocarpicfruit can be distinguished. The desirability of distinguishingbetween the terms ‘seedless’ and ‘parthenocarpic’is pointed out.     

Effect of hydroxyl radical on the scission of cellular wall polysaccharides in vitro of banana fruit at various ripening stages

Fruit ripening is generally attributed to disassembly of cellular wall, particularly due to solubilisation and depolymerisation of pectin and hemicellulose. Experiments were conducted to test effects of hydroxyl radicals (·OH) on the scission of cellular wall polysaccharides from pulp tissues of banana fruit at different ripening stage. Cellular wall materials were isolated from pulp tissues of banana fruit at different ripening stages. Two pectic fractions, water soluble pectin (WSP) and acid soluble pectin (ASP), and two hemicellulosic fractions, 1 M KOH soluble hemicellulose (HC1) and 4 M KOH soluble hemicellulos (HC2), were obtained from the cellular wall materials from pulp tissues, respectively. Effects of ·OH induced by the Fenton reaction on the scission of pectin and hemicellulose in vitro were investigated. As fruit ripening progressed, the sugar components of the WSP, HC1 and HC2 attacked by ·OH showed obvious molecular-mass downshifts. Thus, ·OH caused the disassembly of polysaccharides (WSP, ASP, HC1 and HC2) from cellular walls of pulp tissues of banana fruit, demonstrated by the reduced molecular mass distribution. Moreover, ·OH production in pulp tissues increased significantly as banana fruit ripened, which further help account for the role of ·OH in accelerated fruit ripening.     

Characterization of multiple forms of α-glucan phosphorylase from Musa paradisiaca fruits

Three forms of α-glucan phosphorylase from mature banana fruit pulp separated by ammonium sulfate fractionation and DEAE-cellulose chromatography were anodic at pH 8·6 on starch gel electrophoresis. The three forms differed in sensitivity to the phenolics extracted from immature and mature banana fruit pulp. Only two forms of the enzyme were detected in immature banana fruit pulp.     

Fruit development is actively restricted in the absence of fertilization in Arabidopsis

Flowering plants usually require fertilization to form fruit and seed and to initiate floral organ abscission in structures that do not contribute to the fruit. An Arabidopsis mutant that initiates seedless fruit without fertilization (fwf) or parthenocarpy was isolated and characterized to understand the factors regulating the transition between the mature flower and the initiation of seed and fruit development. The fwf mutant is fertile and has normal plant growth and stature. It sets fertile seed following self-pollination and fertilization needs to be prevented to observe parthenocarpy. The initiation of parthenocarpic siliques (fruit) was found to be dependent upon carpel valve identity conferred by FRUITFULL but was independent of the perception of gibberellic acid, shown to stimulate parthenocarpy in Arabidopsis following exogenous application. The recessive nature of fwf is consistent with the involvement of FWF in processes that inhibit fruit growth and differentiation in the absence of fertilization. The enhanced cell division and expansion in the silique mesocarp layer, and increased lateral vascular bundle development imply FWF has roles also in modulating silique growth post-fertilization. Parthenocarpy was inhibited by the presence of other floral organs suggesting that both functional FWF activity and inter-organ communication act in concert to prevent fruit initiation in the absence of fertilization.     

Effect of parthenocarpy on ovule development in cucumber (Cucumis sativus L.) after pollination with normal and irradiated pollen

In nonparthenocarpic cucumber, analysis of the interaction between season and female receptivity demonstrated two different modes of fruit development and seed set. Spring climatic conditions induced significantly longer ovaries at anthesis with an autonomous fruit set as in natural parthenocarpy. Autumn climatic conditions induced smaller ovaries with fruit set influenced by the pollination stage of the female flower. These differences involve, during fruit development, a regulation of the empty seed number especially at both ends of female receptivity period. Indeed, seasons have no effect on ovule receptivity and fertility measured by full seed number. It is supposed that priority is given to seeds with an embryo in the competition for limited maternal resources in spring as well as in autumn. In spring, the use of irradiated pollen during the whole female receptivity period did not modify the seed set profile. Moreover, a cytological study of 6-day-old ovules pollinated by irradiated pollen has revealed a similar precocious embryogenesis compared to the control. In cucumber, pollination with irradiated pollen involves stenospermocarpy rather than induced parthenocarpy. However, we have not been able to determine whether the early abortive embryogenesis induced by irradiated pollen is gynogenetic or abnormal zygotic.     

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。     

Vegetative Parthenocarpy in the Cactus Pear Opuntia ficus-indica (L.) Mill.

The dependence of fruit development on fertilization was studiedin two clones of Opuntia ficus-indica, Ofer and BSI. Fruitsof the clone Ofer bear fully developed seeds, whereas fruitsof the clone BSI contain only degenerated seeds and it was suspectedthat BSI is parthenocarpic. The two clones differed in theirpattern of fruit development. The increase in fruit fresh weightin Ofer was a result of both peel and pulp growth, whereas inBSI fruit growth was mainly due to pulp growth and the peelhad reached its final weight almost at anthesis. Pulp growthin BSI commenced earlier and was faster than in Ofer, but thefinal pulp weight in BSI was only 64% of that in Ofer. Seedgrowth in BSI was limited to the development of semilignifiedand lignified seed coats, whereas in Ofer 43·5% of theseeds were completely developed, the remainder being similarto those found in BSI. Fruits bearing well-developed seeds werealso found in a 'mutant' of BSI that, like Ofer, contained smallerovules at anthesis than flower of the regular BSI genotype.Germination in vivo and in vitro were similar in BSI and Ofer,but pollen tubes failed to reach the ovules in the regular BSIgenotype, while penetrating the ovules in Ofer and the small-ovuledgenotype of BSI. Good-quality fruits similar to Ofer fruitsin weight but with a higher peel to pulp ratio developed inBSI after flower-sterilization in the spring and in the autumn.In Ofer, sterilized flowers failed to develop fruits in springand partially set fruit in the autumn; the fruits consistedalmost exclusively of peel tissue. It was concluded that BSIis a vegetative parthenocarpic clone, i.e., that pollinationis not required for fruit set and development.Copyright 1993,1999 Academic Press Opuntia ficus-indica, cactus pear, fruit development, parthenocarpy, pollen-tube-growth, fluorescence microscopy     

复方壮果素对香蕉果实生长发育和产量的效应

多年多点试验结果表明,在香蕉断蕾5～7天喷施复方壮果素,对促进香蕉果指生长和提高产量都有明显的效果;喷施壮果素的单指鲜重、果肉重以及果肉中的千物质和淀粉积累基本上能与果指长度、粗度同步增加,且不影响香蕉果实外观和品质。     

香蕉果实XET cDNA的克隆及其在成熟软化的果实果皮和果肉中的表达分析

木葡聚糖内糖基转移酶(Xyloglucan endotransglycosylase,XET)通过分解细胞壁半纤维素多糖的主要成分--木葡聚糖而参与果实软化.为了阐明香蕉(Musa acuminata.Colla cv.GrandNain)果实成熟过程中的软化与细胞壁代谢酶XET基因表达模式的关系,采用RT-PCR和RACE-PCR方法,首次从成熟香蕉果实果肉中分离了编码XT基因的全长cDNA(MA-XET1,全长1 095 bp).序列分析表明,MA-XET1的5'端和3'端的非翻译区分别为66 bp和1 89bp,该片段含有一个完整的开放读码框,编码280个氨基酸,推导的MA-XET1蛋白质中存在XET蛋白的催化活性部位DEIDFEFL.Southern杂交表明,MA-XET1在香蕉基因组中由多拷贝基因编码.Northern分析显示,跃变前期的果肉中,不能检测MA-XET1基因的表达,跃变期的果实果肉中MA-XET1表达增加,跃变后期该基因表达略有减弱;在跃变前期的果实果皮中,MA-XET1的积累较低,跃变期的果实果皮中积累大幅增加,而后迅速下降.Propylene(丙烯,乙烯的类似物)处理降低香蕉果实果皮和果肉的硬度,而且propylene促进MA-XET1在果皮和果肉中的积累.这些结果表明,MA-XET1参与香蕉果实成熟过程中的果皮和果肉软化,并且,MA-XET1的表达在转录水平上受乙烯调控.     

柑橘果实生长发育过程中果实不同部位的4种内源激素含量变化的研究

以单性结实的国庆1号温州蜜柑和自花结实的华农本地早橘为材料,研究了果实生长发育过程中果实不同部位的吲哚乙酸(IAA)、脱落酸(ABA)、赤霉素(GA1/3)和玉米素核苷(ZR)含量的变化。结果表明:(1)国庆1号果皮IAA、GA1/3和ZR含量在幼果阶段均相对较高,随后果皮和果肉IAA含量均趋下降,而在果实膨大期内果肉ABA和果皮、果肉GA1/3、ZR含量均出现上升峰值,果实成熟采收时果皮和果肉ABA含量均明显回升。(2)华农本地早种子、果皮和果肉IAA及其种子ABA含量均在果实膨大期内出现明显峰值,在幼果阶段至果实膨大初期内种子GA1/3和ZR含量均居较高并出现明显上升,对应的果皮、果肉4种内源激素水平均相对较低且变幅小。还就两结实类型柑橘果实生长发育与其内源IAA、ABA、GA1/3和ZR含量动态的关系进行了讨论。     

PRO－LONG涂膜处理对后熟香蕉果实乙烯形成以及其它有关生理变化的影响

香蕉（ＭｕｓａａｃｕｍｉｎａｔａＣｏｌｌａｃｖ．ＤｗａｒｆＣａｖｅｎｄｉｓｈ）果实采后以商业上推荐使用的１．５％Ｐｒｏ－ｌｏｎｇ溶液处理,贮藏于２０℃和７５％相对湿度下,分别测定果实的ＡＣＣ含量、ＭＡＣＣ含量、ＥＦＥ酶活性、乙烯释放、叶绿素含量的变化和果实的硬度变化．结果表明,ＰＲＯ－ＬＯＮＧ处理延缓了香蕉果实果皮的叶绿素降解、硬度的下降以及乙烯释放的增加．在后熟过程中,处理果实的ＡＣＣ含量发生积累．ＡＣＣ含量的高峰在乙烯释放高峰和ＥＦＥ酶活性高峰之前出现．与对照比较,处理果实的ＡＣＣ含量和ＥＦＥ酶活性的高峰延迟了５ｄ出现．在后熟过程中,以Ｐｒｏ－ｌｏｎｇ处理果肉四片,其ＥＦＥ酶活性受部分抑制（抑制率为１９．４５％至４０．５１％）．果实ＭＡＣＣ含量在贮藏起初处于一个较显著水平,随着后熟的发展而逐步增加,但与ＡＣＣ含量的明显增加相比变化是微小的．我们的研究进一步阐明了ＰＲＯ－ＬＯＮＧ涂膜对香蕉果实后熟的影响主要是通过减少氧的供给,部分地抑制了ＥＦＥ酶活性,延缓了乙烯的形成和释放,从而延长了后熟过程．     

植物激素对果树单性结实调控的研究进展

尽管种子与果实的发育过程密切相关,但由于无籽果实提高了果实的品质并延长了货架期,因此无籽果实受到生产者和消费者的广泛青睐。果实的生长受激素调控,而相关研究也初步揭示了激素在单性结实果实形成过程中的作用。本文对单性结实的概念、诱导单性结实的激素种类及功能、诱导机理,以及转基因技术在单性结实果实生产中的应用概况进行了综述,以期为果树单性结实的研究提供参考。     

The effect of frugivory on postdispersal seed removal and germination in the pantropical forest tree Antiaris toxicaria Leschenault

The quality of seed treatment by frugivores has an effect on seed removal after dispersal, seed germination and tree recruitment. We provide information on postdispersal seed removal, germination and subsequent recruitment in tropical forest tree species Antiaris toxicaria in Ghana. We tested whether postdispersal seed removal and germination rates were differentially affected by the following seed treatments: seeds that were spat out by monkeys with all fruit pulp removed and spitting seeds with fruit pulp partially removed as observed in some birds and bats. We used seeds of intact ripened fruits as control. Frugivore seed treatment and distance from bole affected seed removal patterns, whereas intact seeds were significantly removed from all seed stations. The germination success was greater for seeds that were spat out by monkeys and poor for seeds with fruit pulp partially removed and intact fruits. More recruits were recorded at the edge of the adult A. toxicaria canopy radius. There was weak relationship (r² = 0.042) between the number of recruits and distance away from the adult tree. Results suggest that the subsequent recruitment in tropical forest tree species may be enhanced by some frugivore fruit‐handling behaviour where fruit pulp is removed from the seeds without destroying the seeds.     

Seed cleaning behavior by tropical ants and its anti-fungal effect

In tropical forests, ants frequently consume fruit pulp around seeds of vertebrate-dispersed plants, which protects the seeds from infection by fungus and pathogens. Seed cleaning behavior by omnivorous ants was observed in the secondary forests of Bogor botanical garden in West Java. Fruit pulp around the seeds of the rambutan Nephelium lappaceum was completely removed by Pheidole plagiaria, Anoplolepis gracilipes, and other ants. When seed cleaners were excluded, however, many seeds were attacked by fungus and died. Seeds that were cleaned by hand, but not by ants, were similarly attacked. Field experiments on seed cleaning by P. plagiaria revealed that the anti-fungal effect was not merely caused by removal of fruit pulp, and that seed cleaning reduced the development of spores and hypha of fungi. We suggest that the workers apply anti-fungal substances to the fruit pulp and seed surface.