Using flowering times and leaf numbers to model the phases of photoperiod sensitivity in Antirrhinum majus L

A model has been developed that can be used to determine the phases of sensitivity to photoperiod for seedlings subjected to reciprocal transfers at regular intervals between long (LD) and short day (SD) conditions. The novel feature of this approach is that it enables the simultaneous analysis of the time to flower and number of leaves below the inflorescence. A range of antirrhinum cultivars were grown, all of which were shown to be quantitative long-day plants. Seedlings were effectively insensitive to photoperiod when very young (juvenile). However, after the end of the juvenile phase, SD delayed flowering and increased the number of leaves below the inflorescence. Plants transferred from LD to SD showed a sudden hastening of flowering and a decrease in leaf number once sufficient LD had been received for flower commitment. Photoperiod had little effect on the rate of flower development. The analysis clearly identified major cultivar differences in the length of the juvenile phase and the photoperiod-sensitive inductive phase in both LD and SD.     

Flower bud differentiation in Salix pentandra as affected by photoperiod, temperature and growth regulators

Flower bud initiation in seedlings and vegetatively propagated plants of Salix pentandra from different locations has been studied under controlled conditions. In mature plants flower bud formation was induced by 2-chloroethyltrimethylammoniumchloride (CCC) and by short day treatment. The effect of CCC was antagonized by GA₃. The critical photoperiod for flower bud formation was about 18 h for a southern clone (from 49°48'N), but cuttings of a northern ecotype (from 69°39'N) formed flower buds even at 24 h photoperiod. Generally, flower bud formation occurred simultaneously with apical growth cessation. However, apical growth cessation was not a prerequisite for floral initiation and flower buds were also found in elongating plants. Seedlings up to 60 days old did not form flower buds in growth chamber studies. The length of the juvenile phase has not been studied in detail, but cuttings taken from seedlings approximately 20 cm high and 60 days old were able to develop flower buds when treated with CCC. A gradual transition from the juvenile to the mature phase was obtained by repeated pruning of seedlings grown at 18°C and 24 h photoperiod.     

Effects of irradiance on growth and flowering in the shade plant, cineraria

Effects of total irradiance on growth and flowering were studied in cineraria cv. Cindy Blue grown under warm (mean 21°C) glasshouse conditions. Efficiency of light conversion for leaf and shoot dry weight increase were reduced from 0.08 to 0.02 as the mean daily light integral increased from 0.9 to 4.4 MJ m^-2 day^-1 but no significant difference in leaf area were associated with this. Specific leaf area decreased exponentially from 0.07 to 0.02 m²g¹ over the cumulative irradiance range 23 to 127 MJ m^-2 after the start of treatments and thereafter remained stable. A light integral of 19.2 MJ m^-2 were required for initiation of one leaf in plants grown under a daily integral of 4.4 MJ m^-2 day^-1, as compared with only 5.1 MJ m^-2day^-1 required per leaf in plants grown at less than 0.9 MJ m^-2day^-1. Neither chronological duration of juvenile development nor leaf number below the flower was affected by irradiance. However, as the rate of leaf initiation increased with irradiance up to 2.4 MJ m^-2day^-1 so the rate of progress to flower visibility increased linearly with irradiance over the same range. This rate then remained constant from 2.4 to 4.4 MJ m^-2day^-1. Length of the main flowering shoot decreased and the number of flowering shoots increased as irradiance increased from 0.9 to 2.4 MJ m^-2 day^-1 and then remained unchanged by further increases in irradiance.     

拟南芥开花时间调控的分子基础

在合适的时间开花对大多数植物的生存和成功繁衍极为重要。开花时间受错综复杂的环境因素和植物自身的遗传因子影响,由开花调控因子所构成的光周期、春化、温度、赤霉素、自主以及年龄等至少6条既相互独立又相互联系的遗传途径调控。该文综述了有关拟南芥(Arabidopsis thaliana)开花时间调控的分子机制的最新研究进展,并对今后的研究进行了展望。     

高等植物开花时程的基因调控（Ⅰ）

高等植物从营养生长向生殖生长及发育转变的时程具有重要意义,但是了解得很少。近6年来利用分子遗传学方法详细地分析了拟南芥中的这一转变的时程变化,为高等植物开花时程的基因调控提供了一个很好的模式。有关早期或晚期开花表现型的大量突变体及遗传变异得到了阐述。这里谈到的表现型对影响开花转变的环境及内部因子的控制有重大作用。通过分子生物学、遗传学和生理学分析已经鉴定了参与此过程的不同组分,如光识别和昼夜节律（circadian rhythm）因子。另外,通过克隆某些花诱导基因及其相应的靶基因已经对参与开花信号转导途径（signal transduction pathway）的相关因子进行了系统的鉴定,这些开创性工作大大促进了高等植物开花时程的基因表达调控研究及其机理的阐明。本实验室在以黄瓜、新红宝西瓜、西葫芦为材料所获得的部分结果基础上,主要以近六年来在拟南芥方面获得的进展为依据,对高等植物开花时程的基因调控作一系统的总结,并对其开花时程基因调控的机理提出可能的作用理论模型。     

光周期途径核心因子CO的开花调控机制

CONSTANS（CO）基因是生物钟和开花时间基因之间监测日照长度的重要元件,在光周期途径中发挥核心功能。CO可以整合光信号和生物钟信号,诱导开花途径整合子FLOWERINGLOCUST（F即和SUPPRESSOROF OVEREXPRESSION OF CONSTANS 1（SOC1）的表达,进而促进植株开花。本文综述CO基因的开花调控机制,并结合CO基因的研究现状展望了其未来的研究方向。     

Flowering and morphogenic responses of new Aster hybrids to photoperiod

Photoperiod treatments of 13, 14.5, 16 and 17.5 h were used to determine the photoperiodic response of the interspecific Aster hybrids 'Painted Lady', 'Snowflake' and 'Blue Butterfly' belonging to 'Butterfly' series, under glasshouse conditions. Rate of flowering was higher under 13-h photoperiods decreasing up to 16-h photoperiods. The rate of flowering for 13- and 17.5-h photoperiods was nearly similar but under the longest photoperiod flowering was erratic and sometimes abortion of the apical bud was observed. Pholoperiod affected the morphology of the plant. Increasing photo-periods up to 16 h induced an increase of internode length of the main axis, of total length of lateral shoots, the number of ray florets. In a 13-h photoperiod the plants produced a paniculate-racemose shaped inflorescence while in longer photoperiods the inflorescence was paniculate-corymbose shaped.     

Florigen （Ⅱ）： It is a Mobile Protein

The true identity of florigen - the molecule（s） that migrates from leaves to apical meristem to initiate flowering - was notoriously elusive, having made it almost the ＂Bigfoot＂ of plant biology. There was never a lack of drama in the field of florigen study, and florigen researchers have once again experienced such a swing in the last two years. We wrote a minireview last year in this journal （Yu et al. 2006） to excitedly salute, among other discoveries, the notion that the flowering locus T （FT） mRNA might be the molecular form of a florigen. However, this hypothesis was challenged in a little less than two years after its initial proposition, and the original paper proposed that the FT mRNA hypothesis was retracted （Huang et al. 2005; Bohlenius et al. 2007）. Interestingly enough, the FT gene previously proposed to encode a florigen was never challenged. Rather, the FT protein, instead of the FT mRNA, is now believed to migrate from leaves to the apical meristem to promote floral initiation. In this update, we will share with our readers some entertaining stories concerning the recent studies of florigen in five different plant species. In addition to the published reports referenced inthis update, readers may also refer to our previous minireview and references therein for additional background information （Yu et al. 2006）.     

不同光周期对西红花开花和花丝品质的效应比较

为筛选促进西红花开花和提高花丝品质的最佳光周期,以3种不同规格(20～25 g、25～30 g、30～35 g)西红花种球为材料,设置4种光周期处理(8 h/16 h、10 h/14 h、12 h/12 h、14 h/10 h),考察光周期对西红花种球鲜重变化、主芽生长、展叶数量、开花后营养物质含量以及花朵性状和花丝品...     

光周期对春石斛开花及多胺含量的影响

以春石斛为试材,研究光周期对其开花及多胺（腐胺、亚精胺和精胺）含量的影响,以期了解春石斛开花的光周期特性以及期间能源物质多胺的变化规律。结果显示,春石斛短日照处理植株开花较长日照处理的提前约18d,为称量性短日照植物;同时,短日照处理植株的花芽多,开花量犬,花径较长日照大。不同光周期诱导开花过程中,春石斛叶片内腐胺含量最高,波动较大,短日照处理下基本维持比长日照高的水平。亚精胺含量其次,且随生长发育逐渐升高,短日照处理下一直保持比长日照高的水平。精胺含量最低,变化不大,短日照下保持与长日照相同或略高的水平。由此推测,春石斛为称量性短日照植物,高水平的腐胺和亚精胺可能与春石斛花芽的形成有关。     

Juvenility and flowering of Brunonia australis (Goodeniaceae) and Calandrinia sp. (Portulacaceae) in relation to vernalization and daylength

Background and Aims

The time at which plants are transferred to floral inductive conditions affects the onset of flowering and plant morphology, due to juvenility. Plants of Brunonia australis and Calandrinia sp. were used to investigate whether Australian native ephemeral species show a distinct juvenile phase that can be extended to increase vegetative growth and flowering.

Methods

The juvenile phase was quantified by transferring seedlings from less inductive (short day and 30/20°C) to inductive (vernalization or long day) conditions at six different plant ages ranging from 4 to 35 d after seed germination. An increase in days to first visible floral bud and leaf number were used to signify the end of juvenility.

Key Results

Brunonia australis was receptive to floral inductive long day conditions about 18–22 d after seed germination, whereas plants aged 4–35 d appeared vernalization sensitive. Overall, transferring plants of B. australis from short to long day conditions reduced the time to anthesis compared with vernalization or constant short day conditions. Calandrinia sp. showed a facultative requirement for vernalization and an insensitive phase was not detected. Floral bud and branch production increased favourably as plant age at time of transfer to inductive conditions increased. Younger plants showed the shortest crop production time.

Conclusions

Both species can perceive the vernalization floral stimulus from a very young age, whereas the photoperiodic stimulus is perceived by B. australis after a period of vegetative growth. However, extending the juvenile phase can promote foliage development and enhance flower production of both species.     

高等植物开花时程的调控与光受体Ⅰ.开花时程的基因与光受体调控

系统评述了高等植物开花时程的调控与植物光受体的联系.重点说明了控制开花时程的遗传途径以及光周期途径的有关基因的研究进展.影响高等植物开花的最重要的因子之一便是光周期,光周期对高等植物开花的调控是通过相关基因间的相互作用来实现的,这些基因包括参与花启动发育控制基因,昼夜节律时间钟调控基因及光受体信号转导基因.近5年左右的时间通过对拟南芥及其一系列突变体的研究为我们展示了这一热门领域的广阔的前景.     

Mapping-by-Sequencing Identifies HvPHYTOCHROME C as a Candidate Gene for the early maturity 5 Locus Modulating the Circadian Clock and Photoperiodic Flowering in Barley

Phytochromes play an important role in light signaling and photoperiodic control of flowering time in plants. Here we propose that the red/far-red light photoreceptor HvPHYTOCHROME C (HvPHYC), carrying a mutation in a conserved region of the GAF domain, is a candidate underlying the early maturity 5 locus in barley (Hordeum vulgare L.). We fine mapped the gene using a mapping-by-sequencing approach applied on the whole-exome capture data from bulked early flowering segregants derived from a backcross of the Bowman(eam5) introgression line. We demonstrate that eam5 disrupts circadian expression of clock genes. Moreover, it interacts with the major photoperiod response gene Ppd-H1 to accelerate flowering under noninductive short days. Our results suggest that HvPHYC participates in transmission of light signals to the circadian clock and thus modulates light-dependent processes such as photoperiodic regulation of flowering.