浅析单性结实

植物子房不经受精作用而发育成果实的现象叫做单性结实,由单性结实形成的果实称为无籽果实。无籽果实中不含种子或含无胚的种子。在自然界中,单性结实有两种类型,即营养性单性结实和刺激性单性结实。前者在形成无籽果实时是不经任何刺激就能实现的,如香蕉,风梨、菠萝等;而后者在形成无籽果实时是需经花粉或激素刺激才能实现的,如无籽西瓜、无籽番茄、无籽葡萄等。     

转基因技术生产无籽果实的新策略

无籽果实具有许多优点 ,深受人们喜爱。传统无籽果实生产方法存在着诸如单性结实品种少、外用激素施用量不易掌握及四倍体品种较难获得等一系列问题。分子遗传研究表明 ,植物基因组中含有影响单性结实的基因 ,某些来自于细菌的基因也可在植物激素生物合成途径中起调节作用。应用这些目的基因 ,已建立了转基因生产无籽果实的新策略 ,如在种皮或子房特异性启动子控制下的生长素基因或细胞毒素基因的表达及“终止子”技术的运用等 ,这将大规模地促进蔬菜和水果生产 ,提高果蔬产品的市场价值。     

转基因技术生产无籽果实的新策略

无籽果实具有许多优点,深受人们喜爱。传统无籽果实生产方法存在着诸如单性结实品种少、外用激素施用量不易掌握及四倍体品种较难获得等一系列问题。分子遗传研究表明,植物基因组中含有影响单性结实的基因,某些来自于细菌的基因也可在植物激素生物合成途径中起调节作用。应用这些目的基因,已建立了转基因生产无籽果实的新策略,如在种皮或子房特异性启动子控制下的生长素基因或细胞毒素基因的表达及“终止子”技术的运用等,这将大规模地促进蔬菜和水果生产,提高果蔬产品的市场价值。     

单性结实与无籽番茄、无籽西瓜的培育

被子植物传粉受精后 ,胚珠开始发育并产生大量生长素使子房增大发育成果实。但自然界中也有些植物在开花后不通过受精作用子房发育成果实 ,但无种子。因此在发育成熟的果实里 ,有的含种子 ,有的不含种子 ;前者称为有籽果实 ,后者称为无籽果实 ,生物学上也把后者的结实方式称为单性结实。单性结实有天然的单性结实 (或称自动的单性结实 )和刺激性单性结实 (或称被动的单性结实 )。天然的单性结实是指不需要经过传粉刺激和其他刺激 ,子房就发育为无籽果实的 ,如香蕉、凤梨、无籽柑橘、无籽柠檬 ,在番茄、黄瓜和胡椒等植物中也偶有发生。这种类…     

枇杷胚乳愈伤组织的诱导和异常器官的分化

枇杷(Eriobotrya japonica Lindl.)是我国特产的优良亚热带水果。但是,与一般的水果比较,枇杷的种子较多,较大,因而可食用果肉部分的比例较少,所以培育无籽枇杷的研究很有诱人的前景。枇杷果实中种子总重量与果重成正相关,用赤霉素处理能引起单性结实,产生无籽果实。但单性结实的果实通常比有籽的果实小[8]。     

5个生物学易混概念辨析

1 单性生殖与单性结实 单性生殖是由有性生殖细胞（未受精的卵细胞或精子）直接发育而成,属有性生殖中的单性生殖。单性结实是由于雌蕊不能产生正常的生殖细胞或没有受粉使子房发育为无籽果实叫单性结实。     

植物的单性结实

在高中生物必修本第122页上讲到:利用人工合成的一定浓度的生长素溶液处理没有受粉的番茄花蕾,就能获得无籽番茄。这实际上就是番茄的单性结实。 什么叫单性结实呢?凡是不经受精作用而形成不含种子的果实,叫单性结实。单性结实有天然性单性结实和刺激性单性结实之分。天然性单性     

无籽西瓜

果实中完全无籽或有少数在食用时感觉不出的白嫩疵子的西瓜,称为无籽西瓜. 当前国内外研究出来的无籽西瓜,可分为三倍体无籽西瓜和激素诱导无籽西瓜(刺激性单性结实)二种类型. 1.刺激单性结实途径 (1)人工合成激素方法1938年黄昌贤教授在世界第一个用人工合成激素涂于西瓜雌花柱头而取得无籽西瓜.(即用100ppm茶乙酸钠液).但因果型小,形不正,商品性状差,未能用于生产. (2)天然激素法即用4X的雄花,授粉于2X的雌花柱头上,在完全隔离套袋的情况下,人工授粉而成,座果率因2X和4X的品种不同而高低有别,但大白籽(假种子)多,质量不好.但也有质优者如4X一号×兴城红(2X).     

无籽枇杷研究初报

利用冻害果实、生长调节剂诱导、多倍体品种等进行无籽枇杷生产试验,结果表明,生长调节剂诱导及利用多倍体品种是生产无籽枇杷果实的较佳方法。     

自然界中的无籽果实是怎样形成的?

绿色开花植物的个体发育是从受精卵开始的,它在生殖上具有独特的双受精现象。卵细胞受精后发育形成胚(幼小植物的雏体),受精极核发育成胚乳,整个胚珠发育成种子,子房发育成为果实。但自然界中也有些植物在开花后不经过受精作用也能结出果实,但无种子。因此在发育成熟的果实里,有的含种子,有的不含种子;前者称为有籽果实,后者称为无籽果实,生物学上也把后者称为单性结实。在被子植物中,能够结出无籽果实有三种情况:一是不经过授粉和其他刺激而产生果实的,如香蕉、凤梨、无子柑桔、无籽柠檬,在番茄、南瓜、黄瓜、胡椒等植物中也偶有发生;这种…     

Induced parthenocarpy-a way of manipulating levels of endogenous hormones in tomato fruits (Lycopersicon esculentum Mill.) 2. Diffusible hormones

Indol-3-acetic acid (IAA), gibberellin-like substances (GAs), and abscisic acid (ABA) were measured throughout the first 35 days of fruit development in agar diffusates from seeded and parthenocarpic tomato fruits. Parthenocarpic fruit growth was induced with either an auxin (4-CPA), morphactin (CME) or gibberellic acid (GA₃). IAA and GAs were at their highest levels in diffusates during the early stages of fruit growth, whereas diffusible ABA increased later. Most IAA was found in diffusates from auxin-induced and seeded fruits, whereas GAs were at their lowest levels in seeded fruits. There were only minor differences in ABA concentrations regardlesss of the treatments.Levels of diffusible hormones of tomato fruits may be easily manipulated by inducing parthenocarpic fruit growth. In spite of no obvious relationship between fruit growth and hormone levels in this study, induced parthenocarpy is considered a useful tool to further elucidate the role of hormones in fruit development and sink-source interactions.     

Genetic engineering of parthenocarpic fruit development in tomato

Parthenocarpy was engineered in two genotypes of Lycopersicon esculentum Mill. by using the DefH9-iaaM chimeric gene. The parthenocarpic trait consists of fruit set and growth in the absence of fertilization. Seedless parthenocarpic fruits were obtained from emasculated flowers, and fruits with seeds from pollinated flowers. All parthenocarpic tomato plants analysed expressed the DefH9-iaaM gene during flower development. The fruit set percentage of emasculated transgenic flowers was similar to that of control plants. In 7 out of 8 independent transgenic plants, the fresh weight of fruits derived from pollinated or emasculated flowers did not significantly differ from that of fruits obtained by pollination of the control plants. The pH of the parthenocarpic fruit was generally unaffected and the soluble solid concentration was either unchanged or increased. Thus, the DefH9-iaaM gene is a genetic tool that might be used to improve tomato productivity.     

Induced parthenocarpy—a way of changing the levels of endogenous hormones in tomato fruits (Lycopersicon esculentum Mill.) 1. Extractable hormones

Ethylene, indol-3-acetic acid (IAA), gibberellin-like substances (GAs) and abscisic acid (ABA) were analysed in extracts from normal, seed-containing and parthenocarpic tomato fruits throughout fruit development. Parthenocarpic fruit growth was induced with an auxin (4-CPA), morphactin (CME) or gibberellic acid (GA₃) and compared with that of pollinated control fruits. Fruit growth was only affected by the treatment with GA₃, decreasing size and fresh weight by 60%. The peak sequence of hormones during fruit development was ethylene-GAs-IAA-ABA. Seeded fruits contained the highest levels of IAA and ABA but the lowest levels of GAs. Also, in seeded fruits, a high proportion of IAA and ABA was found in the seeds whereas this was not the case for GAs.Hormone levels of tomato fruits may be successfully, easily and reproducibly altered by inducing parthenocarpic fruit growth and thus eliminating development of seeds which are a major source of hormone synthesis. In spite of markedly changed hormone levels, there was no obvious relationship between fruit growth and extractable hormones per se. However, the results indicate that a high ratio of GAs: auxins is unfavourable for growth of tomato fruits.     

Strong synergistic effects of gibberellins with the synthetic cytokinin N-(2-chloro-4-pyridyl)-N-phenylurea on parthenocarpic fruit set and some other fruit characteristics of apple

The induction of parthenocarpic fruit set was investigated using the apple cvs. Golden Delicious and Jonagold. The gibberellins GA₃, GA₄, GA₅ and GA₇ and the synthetic phenylurea-type cytokinin CPPU (N-(2-chloro-4-pyridyl)-N-phenylurea), were applied alone and in combination to unpollinated flowers at the end of petal fall. Gibberellins induced only a marginal final set of parthenocarpic fruits. CPPU sprays were more effective, particularly in the first year. When applied in combination, CPPU and gibberellins had a positive synergistic effect on parthenocarpic fruit set and fruit size, but a negative effect on flower induction the next year. After CPPU + GA sprays, percent fruit set was similar, or greater, compared to natural pollinated trees. The parthenocarpic fruits induced by CPPU + GA had an increased length to diameter ratio. CPPU stimulated, and GA₄ and GA₇ reduced, the russeting of the parthenocarpic fruits. The internal quality of the fruits was hardly affected, but Ca-deficiency symptoms occurred more frequently in parthenocarpic fruits.     

Early anther ablation triggers parthenocarpic fruit development in tomato

Fruit set and fruit development in tomato is largely affected by changes in environmental conditions, therefore autonomous fruit set independent of fertilization is a highly desirable trait in tomato. Here, we report the production and characterization of male‐sterile transgenic plants that produce parthenocarpic fruits in two tomato cultivars (Micro‐Tom and Moneymaker). We generated male‐sterility using the cytotoxic gene barnase targeted to the anthers with the PsEND1 anther‐specific promoter. The ovaries of these plants grew in the absence of fertilization producing seedless, parthenocarpic fruits. Early anther ablation is essential to trigger the developing of the transgenic ovaries into fruits, in the absence of the signals usually generated during pollination and fertilization. Ovaries are fully functional and can be manually pollinated to obtain seeds. The transgenic plants obtained in the commercial cultivar Moneymaker show that the parthenocarpic development of the fruit does not have negative consequences in fruit quality. Throughout metabolomic analyses of the tomato fruits, we have identified two elite lines which showed increased levels of several health promoting metabolites and volatile compounds. Thus, early anther ablation can be considered a useful tool to promote fruit set and to obtain seedless and good quality fruits in tomato plants. These plants are also useful parental lines to be used in hybrid breeding approaches.     

Differential regulation of a fruit-specific 62 kDa protein in developing parthenocarpic (pat-2/pat-2) and seeded tomato fruits

The denatured protein profiles of developing tomato ( Lycopersicon esculentum Mill.) fruits, from the anthesis stage up to fruits at 30% of their final diameter, were examined in a pai-2l pat-2 parthenocarpic line and in its near isogenic non-partheno-carpic line. At anthesis no differences were detected between the protein patterns of ovaries developed on parthenocarpic and non-parthenocarpic plants. In subsequent stages the seeded and seedless fruits differed in the pattern of manifestation of several abundant proteins, none of which seem to be included in seeds The most prominent difference was found in an insoluble protein of 62 kDa; in developing seeded fruits of either the parthenocarpic or the non-parthenocarpic line, its rate of decline was much faster than in seedless fruits. In seeded fruits larger than 4-6 mm in diameter it was scarcely detected, whereas in parthenocarpic seedless 8–10 mm fruits it was still abundant. This protein is fruit specific; it is also enhanced in chemically (n-n-tolyl phthalamic acid) – induced parthenocarpic fruits of the non-parthenocarpic line. The prolonged manifestation in the parthenocarpic fruits results from de novo synthesis of this protein. There are indications that it is not a stress-related protein. This is the first demonstration of an association between the pattern of modulation of a protein and the phenotypic expression of genetically controlled parthenocarpy.     

种子小蜂和空壳果实对生物能源树种黄连木果实和油产量的影响(英文)

黄连木Pistacia chinensis Bunge因果实含油量高, 被作为生物能源树种在我国进行大面积栽培推广和能源开发利用。然而, 专性寄生害虫（主要为黄连木广肩小蜂Eurytoma plotnikovi Nikolskaya）的危害及由单性结实和败育所造成的空壳果实可能影响黄连木的果实产量和质量。为了评价种子害虫和空壳果实对黄连木果实产量和质量的影响, 我们测定了河南省济源市3个黄连木种群40株结果雌树的果实产量和油产量, 同时测定了完好果实、 空壳果实和虫蛀果实等3类果实的干重和含油量。结果表明：（1）虫害率和空壳率分别达22.6%和53.0%, 且不同个体和种群间均存在显著差异（P<0.05）。（2）空壳果实（30.7 mg/果）和虫蛀果实（33.1 mg/果）的干重均不到完好果实（67.4 mg/果）的一半; 空壳果实（3.9%）和虫蛀果实（3.8%）的含油量均显著低于完好果实（39.9%）。（3）实测的果实产量（2.9 kg/树）和油产量（0.6 kg/树）分别仅为期望产量的50%（4.7 kg/树）和33%（1.9 kg/树）, 但在3个种群之间无显著差异。本研究显示小蜂危害和空壳果实对黄连木果实产量和质量能造成严重影响, 在将其作为生物能源树种利用时对此应加以克服。     

Parthenocarpic fruits in wild parsnip: Decoy defence against a specialist herbivore

Summary Parthenocarpy, the production of fruits without viable seeds, is a widespread phenomenon in plants. While failure to effect pollination or fertilization is often cited as the cause of parthenocarpy, this explanation alone is inadequate to explain why plants produce, maintain and further develop fruits. Wild parsnips (Pastinaca sativa) frequently produce parthenocarpic fruit. When parsnip webworms (Depressaria pastinacella), specialist feeders on wild parsnip, were given choices between normal fruit and parthenocarpic fruit, they exhibited a strong preference for parthenocarpic fruit. However, on parthenocarpic fruit, insects fed less efficiently and grew more slowly than insects fed normal fruit. Parthenocarpic fruits, then, may act as decoys that divert herbivores away from fruits that contain plant offspring.