离体植物花芽和花器官的发育研究进展

在近二十几年,尤其是近十年由于离体培养技术的完善和进一步向精确的层次的发展,已使得许多种植物花序、花芽和单独花器官以及部分的花器官在体外成功地进行了培养和尝试,并且对花芽及花器官的离体发育有了更深入的认识。不同植物的花发育需要不同的植物生长调节剂以及它们的不同配比,并且不同植物在其花发育所需要的营养因子也存在着相当大的差异性。这种差异性又随植物器官及花发育的不同阶段而受到加大或缩小。通过对正常花及突变体花进行的离体培养实验研究已经对一些花器官发生过程中的调节程序有了新的了解。利用离体培养技术,包括刚发展起来的薄层细胞培养技术在阐明花发育的机理、形态建成的分子机制以及成花梯度的物质基础等问题上具有广阔的潜力。     

Flower Formation in Excised Tobacco Stem Segments: III. Deoxyribonucleic Acid Content in Stem Tissue of Vegetative and Flowering Tobacco Plants

A method has been developed that extracts DNA from stem tissue of flowering tobacco plants, Nicotiana tabacum cv. Wis. 38. The DNA content of stem tissue from a flowering tobacco plant is correlated with its capacity to flower in vitro. Stem segments known to form 100% floral buds contain 10 times more DNA per gram fresh weight than segments that form 5% floral buds and 95% vegetative buds, and in the uppermost 28 centimeters of flowering tobacco plant stems the DNA content decreases roughly in parallel with the floral gradient.     

大岩桐花瓣切块离体培养高频率花芽再生

该文报道了大岩桐花瓣切块离体培养再生花现象,花瓣切块再生花有两种方式：一种是仅再生花芽（命名为BF）;另一种是既再生花芽也再生营养芽（命名为BF＋V）。花芽再生的能力与光照、花芽大小及培养基中赤霉素和细胞分裂素浓度紧密相关。当培养基中含有1.0 mg/L GA3时,BA的添加会显著增加总花芽（BF＋BF＋V）的形成率,添加0.5 mg/L BA时,总花芽形成率达100%。在暗中培养时,BF达93.4%。不同大小花芽的花瓣再生花的能力不同,7 mm直径花芽的BF最高,达86.7%。同时,对花芽再生过程中花瓣切块的组织结构形态变化也进行了观察。     

烟草花柄愈伤组织花芽分化的能力(简报)

来源于开花植株的外植体(如花柄、花序轴等)具有在离体培养条件下直接分化花芽的能力,这一现象已在数十种植物的组织培养中得到证实。但是,这种成花能力能否保留在由这些外植体形成的愈伤组织之中?已有报道在风信子、布罗瓦利亚花、石龙芮、大蒜、矮通泉草等值物的愈伤组织中得到无     

Flower formation in vitro in a quantitative short-day tobacco: interrelation between photoperiod and infructescence development

The flowering response of thin layers excised from branch internodes of Nicotiana tabacum cv. Maryland Catterton (quantitative short-day plant for induction) was studied under three photoperiodic treatments. The explants were excised from inflorescences bearing flowers only, flowers and green fruits, or from infructescences with green fruits only. The aim of the study was to investigate the post-inductive photoperiodic effects on in vitro flower bud formation in a quantitative short-day tobacco and the relation with infructescence development. Short days quantitatively enhanced the flower bud regeneration capacities of explants in all stages of development, both as number of explants induced to produce flowers and as mean number of flowers per explant. There was no significant difference in flower bud formation on explants of the first two stages, which produced much more flowers than those of the third stage. Observations in planta showed that, during the 20 days separating the second stage from the first stage, there was no significant difference in the number of floral buds and flowers present on the inflorescence; however, the branch internodes lengthened, as did the floral buds and flowers. During the 10 days leading to the third stage, the number of capsules did not change significantly, but a high rate of floral abscission occurred. The present results show that in Nicotiana tabacum cv. Maryland Catterton short day quantitatively controls not only the inductive step of the flowering process, but also affects the capacity to regenerate flower buds during the late post-inductive phases. The responsiveness to the photoperiodic signal decreases only when the plant exhibits only fruits.     

Histological and immunohistochemical studies on flower induction in the olive tree (Olea europaea L.)

The aim of this research was to study flower bud differentiation processes in two oil olive cultivars from Tuscan germplasm (Leccino and Puntino). The effect of fruit-set was studied using 'ON' (with fruits) and 'OFF' (without fruits) shoots. Axillary buds were periodically collected at different phenological stages, from endocarp sclerification (July) until budbreak in the following spring. Thin sections were analysed using histology (apex size), histochemistry (RNA, starch and soluble carbohydrates) and cytokinin immunocytochemistry (zeatin localisation). The micromorphological observations and histochemical procedures did not allow us to distinguish axillary buds sampled from 'ON' and 'OFF' shoots. Cytokinin immunocytochemistry revealed early different localisation patterns between 'ON' and 'OFF' samples. Zeatin accumulated only in 'OFF' axillary bud meristems, particularly in July, when endocarp sclerification of fruits from the previous flowering is taking place. At this time, a strong RNA signal was also observed. Both these signals were correlated with floral evocation, and their coincidence with a phenological stage of development provided a useful tool to determine the time when axillary buds switch from the vegetative to the reproductive phase.     

Responsiveness to abscisic acid of embryos of dormant oat (Avena sativa) seeds. Involvement of ABA-inducible proteins

An in vitro bioassay system for floral bud formation has been established using Nicotiana tabacum L. cv. MC, explants excised from floral stalks cultured on modified Murashige-Skoog medium containing excess auxin and antiauxin. Three auxins. indolyl-3-acetic acid (IAA), 4-chloroindolyl-3-acetic acid and 5,6-dichloroindolyl-3-acetic acid, were tested for floral bud-forming activity; IAA was most efficient. Three antiauxins. 5,7-dichlorindolyl-3-isobutyric acid (5,7-Cl₂-HBA), p -chlorophenoxyiso butyric acid and 2,3,5-triiodobenzoic acid, were tested for the ability to reverse the inhibition of floral bud formation caused by excess IAA. Only 5,7-Cl₂-HBA was very effective. Leaf exudates from short day- and long day-treated tobacco plants were added to the bioassay system which contained 1 µ M 6-benzylaminopurine, 5 µ M IAA and 5 µ M 5, 7-Cl₂-HBA, Interestingly, only the leaf exudate from short day-treated plants stimulated floral bud formation. Moreover, the buds produced grew into large. well-developed ones with shapes similar to those of the natural floral buds of intact tobacco plants.     

A MADS domain gene involved in the transition to flowering in Arabidopsis

Flowering time in many plants is triggered by environmental factors that lead to uniform flowering in plant populations, ensuring higher reproductive success. So far, several genes have been identified that are involved in flowering time control. AGL20 (AGAMOUS LIKE 20) is a MADS domain gene from Arabidopsis that is activated in shoot apical meristems during the transition to flowering. By transposon tagging we have identified late flowering agl20 mutants, showing that AGL20 is involved in flowering time control. In previously described late flowering mutants of the long-day and constitutive pathways of floral induction the expression of AGL20 is down-regulated, demonstrating that AGL20 acts downstream to the mutated genes. Moreover, we can show that AGL20 is also regulated by the gibberellin (GA) pathway, indicating that AGL20 integrates signals of different pathways of floral induction and might be a central component for the induction of flowering. In addition, the constitutive expression of AGL20 in Arabidopsis is sufficient for photoperiod independent flowering and the over-expression of the orthologous gene from mustard, MADSA, in the classical short-day tobacco Maryland Mammoth bypasses the strict photoperiodic control of flowering.     

A Developmental Pattern of Flowering in Colored <Emphasis Type="Italic">Zantedeschia</Emphasis> spp.: Effects of Bud Position and Gibberellin

The restricted flowering of colored cultivars ofZantedeschia is a consequence of developmental constraints imposed by apical dominance of the primary bud on secondary buds in the tuber, and by the sympodial growth of individual shoots. GA₃ enhances flowering inZantedeschia by increasing the number of flowering shoots per tuber and inflorescences per shoot. The effects of gibberellin on the pattern of flowering and on the developmental fate of differentiated inflorescences along the tuber axis and individual shoot axes were studied in GA₃ and Uniconazole-treated tubers. Inflorescence primordia and fully developed (emerged) floral stems produced during tuber storage and the plant growth period were recorded. Days to flowering, percent of flowering shoots and floral stem length decreased basipetally along the shoot and tuber axes. GA₃ prolonged the flowering period and increased both the number of flowering shoots per tuber and the differentiated inflorescences per shoot. Activated buds were GA₃ responsive regardless of meristem size or age. Uniconazole did not inhibit inflorescence differentiation but inhibited floral stem elongation. The results suggest that GA₃ has a dual action in the flowering process: induction of inflorescence differentiation and promotion of floral stem elongation. The flowering pattern could be a result of a gradient in the distribution of endogenous factors involved in inflorescence differentialtion (possibly GAs) and in floral stem growth. This gradient along the tuber and shoot axes is probably controlled by apical dominance of the primary bud. Online publication: 7 April 2005     

The Maryland mammoth allele reduces floral stimulus activity in stem piece explants of Nicotiana tabacum (Solanaceae)

The response of axillary buds to floral stimulus activity in stem pieces was examined in two near-isogenic cultivars of tobacco that differ in the recessive maryland mammoth (mm) allele, which confers short-day behavior. All axillary buds from day-neutral plants assayed on six-internode stem pieces made few nodes (less than 20) before flowering, while axillary buds from plants homozygous for mm assayed on six-internode stem pieces either did not flower in noninductive conditions or made many nodes before flowering in inductive conditions. About 80% of day-neutral axillary buds grafted onto day-neutral stem pieces did not respond to floral stimulus in stem pieces, indicating that the floral stimulus in stem pieces is ephemeral. In other graft combinations, the proportion of axillary buds that did respond to floral stimulus in stem pieces was substantially reduced from the 20% of day-neutral buds on day-neutral stem pieces that responded. These results indicate that the mm allele probably reduces both the amount of floral stimulus activity in stem pieces and the competence of axillary buds to respond.     

Ca2+对黄瓜子叶离体培养物花芽分化的影响

黄瓜子叶离体培养物分化培养 0～ 8d期间 ,添加Ca2 有利于花芽分化 ,花芽分化率可从Ca2 0mmol/L的 (7.9± 5 .6 ) %上升到Ca2 6mmol/L的(31.7± 4.0 ) % ;0～ 2d和 2～ 4d无钙脉冲处理不利于花芽分化 ,高钙脉冲处理的花芽分化率比对照略高 ;4～ 6d和 6～ 8d高钙脉冲不利花芽分化 ,而无钙脉冲处理使花芽分化率上升很多。尤其是在 4～ 6d ,高钙处理使花芽分化率从 (2 2± 1.5 ) %下降到 (15 .7±3 .5 ) %。而无钙处理使花芽分化率从 (2 2 .4± 1.4) %上升到 (4 3± 3 .5 ) %。表明 0～ 8d期间不同时间段对Ca2 的需求是有差别的。相关性分析表明 :0～ 8d期间外源Ca2 影响花芽分化率与总芽中花芽比例极显著相关 ,提示Ca2 可能影响子叶向花芽或营养芽分化的趋势。本文结合已报道的黄瓜子叶培养物花原基形成的时程 ,分析了Ca2 对花原基形成和分化的影响     

Tissue 11In vitro Bud Formation on Explants from the Inflorescence of Nicotiana tabacum L.

Croes, A. F., Creemers-Molenaar, T., van den Ende, G., Kemp,A. and Barendse, G. W. M. 1985. Tissue age as an endogenousfactor controlling in vitro bud formation on explants from theinflorescence of Nicotiana tabacum L.—J. exp. Bot. 36:1771–1779. The in vitro formation of generative buds was studied on explantsfrom flower and fruit stalks and from internodes of the floralramifications of tobacco. A floral gradient was found to existalong the axis of the branch. The gradient concerns the numberof flower buds formed in vitro and is present in both typesof tissues. The number of flower buds is greater on tissuesfrom the apical than from the basal portion of the branch. Thecapacity to generate these buds is largely determined by tissueage at the moment of the excision. Consequently, the gradientmoves along the axis during the outgrowth of the inflorescence. The alternative possibility that some apex-derived stimuluspredetermines the morphogenetic capacity of the tissue priorto excision is excluded by the observation that the gradientremains virtually unaltered if the apex is removed one weekbefore the onset of culturing. Auxin affects the floral gradient Increasing the auxin concentrationin internode tissue culture causes a steeper gradient of flowerbud generation by almost completely abolishing bud formationon older tissues. Key words: Auxin, flower buds, gradient, tissue culture, tobacco     

毛茛状金莲花不同花期的花特征和访花昆虫的变化及表型选择

为了研究植物生长季内开花时间对花特征表型选择的影响,我们以青藏高原东缘高寒草地的毛茛状金莲花Trollius ranunculoides)为实验材料,在生长季内不同开花时间(花前期、花末期)测定花特征,观察访花昆虫的类群和访花频率,生长季结束后收集种子.根据昆虫访花的喜好和季节内类群与访花频率的变化,分析了不同开花时间毛茛状金莲花的花特征与昆虫的选择;并用种子产量表示雌性适合度,估计了毛茛状金莲花的花特征在不同开花时间所受的表型选择.结果表明:不同花期植物的花特征有显著差异,相应的访花昆虫的类群和频率也存在差异,不同类群昆虫访花喜好也不一样.蜂喜好花瓣和花萼较宽、花茎短和花茎数少的个体,这正符合花前期的特征,因而蜂的访花频率在花前期较高;蝇对花特征没有明显的偏好.而通过雌性适合度估计毛茛状金莲花花特征所受的表型选择则是:花前期,花茎较长和花茎数多的植株适合度大;花末期,花茎数多的植株适合度大.我们的研究表明:在植物生长季,花期的分化伴随着传粉昆虫活动的变化.不同花期,访花昆虫的变化可能对植物花特征的分化起了至关重要的作用.但是访花昆虫对花特征的选择与通过雌性适合度估计植物受到的选择不尽相同,这可能是由于其他因素造成的.     

Floral scent emission is the highest at the second night of anthesis in Lonicera japonica (Caprifoliaceae)

Floral color change in diverse plants has been thought to be a visual signal reflecting changes in floral rewards, promoting pollinator foraging efficiency as well as plant reproductive success. It remains unclear whether olfactory signals co-vary with floral color change. We investigated the production rhythms of floral scent and nectar associated with floral color change in Lonicera japonica. The flowers generally last 2–3 days. They are white on opening at night (N1) and become light yellow the following day (D1), yellow on the second night (N2), and golden on the second day of flowering (D2). Our measurements in the four stages indicated that nectar production decreased significantly from N1 and D1 to N2 and D2, tracking the floral color change. A total of 34 compounds were detected in floral scent and total scent emission was significantly higher in N2 than in the other three stages. The scent emission of three major compounds, Linalool, cis-3-Hexenyl tiglate, and Germacrene D was also significantly higher in N2, but the relative content of Linalool decreased gradually, cis-3-Hexenyl tiglate increased gradually, and the relative content of Germacrene D did not differ among the four measured stages. Greater scent emission by night than by day suggested a strong olfactory signal to attract nocturnal hawkmoths, the effective pollinators. However, floral scent rhythms in the four stages did not match the color change and nectar secretion, suggesting that floral color (visual) and scent (olfactory) in this species may play different roles in attracting or filtering various visitors.     

Proteins from the FLOWERING LOCUS T‐like subclade of the PEBP family act antagonistically to regulate floral initiation in tobacco

Flowering is an important agronomic trait that often depends on the integration of photoperiod, vernalization, gibberellin and/or autonomous signaling pathways by regulatory proteins such as FLOWERING LOCUS T (FT), a member of the phosphatidylethanolamine‐binding protein (PEBP) family. Six PEBP family proteins control flowering in the model plant Arabidopsis thaliana, and their regulatory functions are well established, but variation in the number and structural diversity of PEBPs in different species means their precise functions must be determined on a case‐by‐case basis. We isolated four novel FT‐like genes from Nicotiana tabacum (tobacco), and determined their expression profiles in wild‐type plants and their overexpression phenotypes in transgenic plants. We found that all four genes were expressed in leaves under short‐day conditions, and at least NtFT3 expression was restricted to phloem companion cells. We also found that the NtFT1, NtFT2 and NtFT3 proteins are floral inhibitors (atypical for FT‐like proteins), whereas only NtFT4 is a floral inducer. We were unable to detect the expression of these genes under long‐day conditions, suggesting that all four tobacco FT‐like proteins may control flowering in response to short days. Phylogenetic analysis of PEBP family proteins and their functions in different solanaceous species confirmed that gene duplication and divergence within the FT‐like clade has led to the evolution of antagonistic regulators that may help to fine‐tune floral initiation in response to environmental cues.     

The effect of photoperiod on flower formation in vitro in a quantitative short-day cultivar of Nicotiana tabacum

Superficial cell layers of a quantitative short-day tobacco plant ( Nicotiana tabacum L. cv. White Burley) were excised from different parts of the inflorescence (i.e. pedicels, branch internodes, rachises), and cultured in continuous darkness, continuous light or 8 h light/16 h dark daily. The flowering response in vitro of the different types of explants was investigated with respect to the effect of light on the post-evocation phases of the flowering process and explant commitment. Treatment effect was qualitatively and quantitatively influenced by explant origin. Three morphogenic features were observed: flower neoformation, caulogenesis and rhizogenesis (the latter on rachis explants only). Under all treatments, the highest flowering potential was shown by pedicels, while the highest vegetative potential was shown by rachises. Branch internodes showed an intermediate response, but with a tendency towards caulogenesis, which probably reflects their phylogenetic origin. Thus, opposite gradients of the neoformation of flowering and vegetative buds on explants were observed under all treatments. Pedicels formed new single flowers rather than inflorescences, while rachises regenerated mainly inflorescences. In darkness, flowering was limited mostly to pedicels. Vegetative bud formation was higher than floral bud regeneration in all types of explant. Continuous light enhanced the flowering response mostly in pedicel and branch internode explants. Short days enhanced flower bud formation in vitro on all types of explant. Results with respect to microsporogenesis, flower and inflorescence anomalies observed under darkness also seem to support the existence of a quantitative photoperiodic control on floral neoformation in vitro in this plant. These results suggest that in Nicotiana tabacum cv. White Burley in vivo floral induction, initiation and development are governed by the same photoperiodic requirements.