Growth and development of Avena fatua (Wild-oat) in the field

The growth and development of field-grown Avena fatua plants were studied for autumn and spring sowings in two consecutive years. The duration of various growth stages from sowing until anthesis was quantified in terms of thermal time (accumulated degree days) or photothermal time (degree days modified by photoperiod). Base temperatures and photoperiods for developmental phases were estimated as those which minimised the coefficient of variation among sowing dates. Relationships were derived between leaf emergence, canopy height, plant leaf area, and photothermal time. Stem extension and flowering occurred earlier in autumn-sown plants than spring-sown plants. Autumn-sown plants produced more leaves on the main stem, and had greater leaf area and above-ground biomass at anthesis than spring-sown plants.     

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.     

Effect of Gibberellic Acid and Phosfon on the Critical Dark Period Reqnirement for Flowering of Impatiens balsamina cv. Rose

The critical dark period requirement for flowering of Impatiens balsamina L. cv. Rose, an obligate short day plant, is about 8.5 hours. While GA₃ completely substituted for the dark period requirement, Phosfon prolonged it to 9.5 hours. GA₃ hastened and Phosfon delayed the initiation of floral buds under all photoperiods. Floral buds opened into flowers only during 8 and 14 hour photoperiods in control and Phosfon-treated plants but during all photoperiods in GA₃-treated ones. The delay in floral bud initiation and flowering was correlated with shifting up of the node bearing the first floral bud and flower respectively. While GA₃ increased the numher of floral buds and flowers in all photoperiods except 8-hour, Phosfon increased their number in the 14-hour photoperiod only. The number of flowering plants decreased with increasing photoperiod regardless of GA₃ and Phosfon application. The effect of Phosfon was completely or partially overcome, depending upon the photoperiod, by simultaneous application of GA₃.     

Day length affects the dynamics of leaf expansion and cellular development in Arabidopsis thaliana partially through floral transition timing

Background and Aims: Plant aerial development is well known to be affected by daylength in terms of the timing and developmental stage of floraltransition. Arabidopsis thaliana is a ‘long day’plant in which the time to flower is delayed by short days andleaf number is increased. The aim of the work presented herewas to determine the effects of different day lengths on individualleaf area expansion. The effect of flower emergence per se onthe regulation of leaf expansion was also tested in this study. Methods: Care was taken to ensure that day length was the only sourceof micro-meteorological variation. The dynamics of individualleaf expansion were analysed in Ler and Col-0 plants grown underfive day lengths in five independent experiments. Responsesat cellular level were analysed in Ler plants grown under variousday lengths and treatments to alter the onset of flowering. Key Results: When the same leaf position was compared, the final leaf areaand both the relative and absolute rates of leaf expansion weredecreased by short days, whereas the duration of leaf expansionwas increased. Epidermal cell number and cell area were alsoaltered by day-length treatments and some of these responsescould be mimicked by manipulating the date of flowering. Conclusions: Both the dynamics and cellular bases of leaf development arealtered by differences in day length even when visible phenotypesare absent. To some extent, cell area and its response to daylength are controlled by whole plant control mechanisms associatedwith the onset of flowering.     

Effect of Vernalization,Photoperiod, and Light Quality on the Flowering Phenotype of Arabidopsis Plants Containing the FRIGIDA Gene

We have compared the flowering response to vernalization, photoperiod, and far-red (FR) light of the Columbia (Col) and Landsberg erecta (Ler) ecotypes of Arabidopsis into which the flowering-time locus FRIGIDA (FRI) has been introgressed with that of the wild types Col, Ler, and San Feliu-2 (Sf-2). In the early-flowering parental ecotypes, Col and Ler, a large decrease in flowering time in response to vernalization was observed only under short-day conditions. However, Sf-2 and the Ler and Col genotypes containing FRI showed a strong response to vernalization when grown in either long days or short days. Although vernalization reduced the responsiveness to photoperiod, plants vernalized for more than 80 d still showed a slight photoperiod response. The effect of FRI on flowering was eliminated by 30 to 40 d of vernalization; subsequently, the response to vernalization in both long days and short days was the same in Col and Ler with or without FRI. FR-light enrichment accelerated flowering in all ecotypes and introgressed lines. However, the FR-light effect was most conspicuous in the FRI-containing plants. Saturation of the vernalization effect eliminated the effect of FR light on flowering, although vernalization did not eliminate the increase of petiole length in FR light.     

Induction and floral determination in the terminal bud of Nicotiana tabacum L. cv. Maryland Mammoth,a short-day plant

Floral determination in the terminal bud of the short-day plant Nicotiana tabacum cv. Maryland Mammoth has been investigated. Plants grown continuously in short days flowered after producing 31.4±1.6 (SD) nodes while plants grown continuously in long days did not flower and produced 172.5±9.5 nodes after one year. At various ages, expressed as number of leaves that were at least 1.0 cm in length above the most basal 10-cm leaf, one of three treatments was performed on plants grown from seed in short days: 1) whole plants were shifted from short days to long days, 2) the terminal bud was removed and then rooted and grown in long days, and 3) the terminal bud was removed and then rooted and grown in short days. Whole plants flowered only when shifted from short days to long days at age 15 or later. Only rooted terminal buds from plants at age 15 or older produced plants that flowered when grown in long days. Only terminal buds from plants at age 15 or older that were rooted and grown in short days produced the same number of nodes as they would have produced in their original locations while buds from younger plants produced more nodes than they would have in their original locations. Thus, determination for floral development in the terminal bud, as assayed by rooting, is simultaneous with the commitment to flowering as assayed by shifting whole plants to non-inductive conditions.Abbreviations LD long day(s) - SD short day(s) - DN dayneutral     

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.     

The Effects of Temperature and Light Integral on the Phases of Photoperiod Sensitivity inPetuniaxhybrida

Flowering in petunias is hastened by long days, but little isknown about when the plants are most sensitive to photoperiod,or how light integral or temperature affect such phases of sensitivity.The effects of these factors on time to flowering was investigatedusing reciprocal transfer experiments between long (16 h d^-1)and short days (8 h d^-1). The effect of light integral on thephases of photoperiod sensitivity was examined using two sowingdates and a shading treatment (53% transmission). The effectsof temperature were investigated by conducting reciprocal transferexperiments in glasshouse compartments at five temperature regimes(means of 13.7, 19.2, 22.3, 25.0 and 28.7 °C). The lengthof the photoperiod-insensitive juvenile phase of development,when flowering cannot be induced by any environmental stimulus,was sensitive to light integral; low light integrals prolongedthis phase, from 23 d at 2.6 MJ m^-2d^-1to 36 d at 1.6 MJ m^-2d^-1(totalsolar radiation). The length of this development phase was shortest(12.5 d) at 21 °C; it was longer under cooler (21 d at 13.5°C) and warmer temperatures (17.6 d at 28.3 °C). Afterthis phase, time to flowering was influenced greatly by photoperiod,with long days hastening flowering by between 28 and 137 d,compared with short days. Plants also showed some sensitivityto both temperature and light integral during this phase, butthe duration of the final phase of flower development, duringwhich plants were photoperiod-insensitive, was dependent primarilyon the temperature at which the plants were grown; at 14.5 °C,33.9 d were required to complete this phase compared with 11.4d at 25.5 °C. The experimental approach gave valuable informationon the phases of sensitivity to photothermal environment duringthe flowering process, and could provide the basis of a morephysiologically-based quantitative model of flowering than hashitherto been attempted. The information is also useful in thescheduling of lighting and temperature treatments to give optimalflowering times of high quality plants.Copyright 1999 Annalsof Botany Company Petunia,Petuniaxhybrida, juvenility, flowering, photoperiod, temperature, light integral, reciprocal transfer.     

Improving quantitative flowering models through a better understanding of the phases of photoperiod sensitivity.

A quantitative understanding of the phases of sensitivity to photo-thermal environment is important if the accuracy of flowering models is to be improved and if the timing of long and short day treatments in protected cropping is to be optimized. A simple method of quantifying the duration of the phases of sensitivity to photoperiod is through the use of reciprocal transfer experiments where plants are transferred between long and short days at regular intervals throughout development. The advantages and disadvantages of different analytical approaches used to analyse such data sets are examined. Inconsistencies between the approaches are highlighted, as are differences in the way authors have interpreted data. The problem of confounding the effects of photoperiod and light integral is considered, as is the need to separate the number of inductive cycles needed for flower commitment from the length of the juvenile phase. The effects of photo-thermal environment on the duration of these phases of photoperiod sensitivity are discussed, together with topics requiring further development.     

水稻开花期调控的分子机理研究进展

水稻准确地感知外部环境信号,通过内部复杂的基因网络做出反应,在一年中最适合的时候开花繁殖。与长日促进长日模式植物拟南芥开花相反,短日促进短日模式植物水稻开花。通过对水稻和拟南芥的开花期调控机理的对比分析,发现水稻和拟南芥有着一些相对保守的开花期控制基因,其调控机理也是相似的。另外,水稻也有一些独特的开花期控制基因和开花途径。本文着重从光周期对水稻开花期的调控途径和作用机理角度进行了阐述,并对水稻开花期的自然变异与其育种应用、生物钟关联基因、光中断现象和临界日长现象以及开花期与产量的关系进行了总结。     

A Norway spruce FLOWERING LOCUS T homolog is implicated in control of growth rhythm in conifers

Growth in perennial plants possesses an annual cycle of active growth and dormancy that is controlled by environmental factors, mainly photoperiod and temperature. In conifers and other nonangiosperm species, the molecular mechanisms behind these responses are currently unknown. In Norway spruce (Picea abies L. Karst.) seedlings, growth cessation and bud set are induced by short days and plants from southern latitudes require at least 7 to 10 h of darkness, whereas plants from northern latitudes need only 2 to 3 h of darkness. Bud burst, on the other hand, is almost exclusively controlled by temperature. To test the possible role of Norway spruce FLOWERING LOCUS T (FT)-like genes in growth rhythm, we have studied expression patterns of four Norway spruce FT family genes in two populations with a divergent bud set response under various photoperiodic conditions. Our data show a significant and tight correlation between growth rhythm (both bud set and bud burst), and expression pattern of one of the four Norway spruce phosphatidylethanolamine-binding protein gene family members (PaFT4) over a variety of experimental conditions. This study strongly suggests that one Norway spruce homolog to the FT gene, which controls flowering in angiosperms, is also a key integrator of photoperiodic and thermal signals in the control of growth rhythms in gymnosperms. The data also indicate that the divergent adaptive bud set responses of northern and southern Norway spruce populations, both to photoperiod and light quality, are mediated through PaFT4. These results provide a major advance in our understanding of the molecular control of a major adaptive trait in conifers and a tool for further molecular studies of adaptive variation in plants.     

Photoperiod Sensitivity during Flower Development of Opium Poppy (Papaver somniferum L.)

Photoperiod is a major factor in flower development of the opiumpoppy (Papaver somniferum L. ‘album DC’) which isa long-day plant. Predicting time to flower in field-grown opiumpoppy requires knowledge of which stages of growth are sensitiveto photoperiod and how the rate of flower development is influencedby photoperiod. The objective of this work was to determinewhen poppy plants first become sensitive to photoperiod andhow long photoperiod continues to influence the time to firstflower under consistent temperature conditions. Plants weregrown in artificially-lit growth chambers with either a 16-hphotoperiod (highly flower inductive) or a 9-h photoperiod (non-inductive).Plants were transferred at 1 to 3-d intervals from a 16- toa 9-h photoperiod andvice versa . All chambers were maintainedat a 12-h thermoperiod of 25/20 °C. Poppy plants becamesensitive to photoperiod 4 d after emergence and required aminimum of four inductive cycles (short dark periods) beforethe plant flowered. Additional inductive cycles, up to a maximumof nine, hastened flowering. After 13 inductive cycles, floweringtime was no longer influenced by photoperiod. These resultsindicate that the interval between emergence and first flowercan be divided into four phases: (1) a photoperiod-insensitivejuvenile phase (JP); (2) a photoperiod-sensitive inductive phase(PSP); (3) a photoperiod-sensitive post-inductive phase (PSPP);and (4) a photoperiod-insensitive post-inductive phase (PIPP).The minimum durations of these phases forPapaver somniferum‘album DC’ under the conditions of our experimentwere determined as 4 d, 4 d, 9 d, and 14 d, respectively. Anthesis; days to flowering; flower bud; opium poppy; Papaver somniferum L.; photoperiod; photoperiod sensitivity; predicting time to flowering; transfer     

Flowering in Lentil (Lens culinaris Medic.): The Duration of the Photoperiodic Inductive Phase as a Function of Accumulated Daylength above the Critical Photoperiod

The durations from emergence to the appearance of first flowerbuds and to first open flowers were recorded in three genotypesof lentil (Lens culinaris Medic.) when plants were transferredfrom short days (either 8 or 10 h) to long days (16 h), or viceversa, after various times from emergence. These results werecompared with those of control treatments in which plants remainedin either short or long days throughout. Four developmentalphases were identified: pre-emergence, pre-inductive, inductiveand post-inductive. The first two phases and the last are insensitiveto photoperiod, but are probably sensitive to temperature. Theduration of the inductive phase, which has to be completed beforeflowering can occur at the end of the post-inductive phase,can be predicted by assuming that its reciprocal is a linearfunction of both photoperiod and temperature. It follows thatthe critical photoperiod decreases with increase in temperatureand that the duration of the inductive phase can be calculatedfrom a summation of the amounts by which successive daylengthsexceed the critical photoperiod until a value (‘the photoperiodicsum’) characteristic of the genotype is reached. The implicationsof these findings for predictive field models of time to floweringin lentils are discussed. Lens culinaris Medic., lentil, flowering, critical photoperiod, photoperiodic sum, temperature, developmental phases, field models     

植物开花逆转研究进展

介绍了植物开花逆转的概念,类型,发生条件,综述了在形态发生,生理,分子生物学等方面的研究进展,探讨了将开花逆转应用于植物发育生物学研究的可能性,作者提出,采用“诱导－非诱导－逆转”三位一体的实验系统,可提高植物光周期反应研究试验结果的可靠性,特别是可以提高在研究开花机理时的基因表达时空性方面的可靠性。     

植物开花逆转研究进展

介绍了植物开花逆转的概念、类型、发生条件,综述了在形态发生、生理、分子生物学等方面的研究进展,探讨了将开花逆转应用于植物发育生物学研究的可能性。作者提出,采用“诱导—非诱导—逆转”三位一体的实验系统,可提高植物光周期反应研究试验结果的可靠性,特别是可以提高在研究开花机理时的基因表达时空性方面的可靠性。     

Photoperiod–temperature phase lag: A universal environmental context of seasonal developmental plasticity

Seasonal developmental plasticity, which consists of season-dependent alternations of developmental processes, has evolved to produce optimal phenotypes depending on specific periods in a year. For example, many phenological events in plants, such as flowering, fruiting, bud blast, bud formation, and growth cessation, are often controlled seasonally. Although temperature and photoperiod are the two major seasonal cues for such responses, the importance of phase lag between annual oscillations of the two signals has been unexplored, despite its universal nature in the context of seasonal environments. In this article, the phase-lag calendar hypothesis (New Phytologist, 210, 2016, 399), especially the one between temperature and photoperiod, is explained using meteorological data obtained from central Japan as an example. We set forth to show how, for a narrow window in time of a couple of weeks in a year, simple threshold responses to these two signals that differ in annual oscillation phases are enough to make developmental plasticity to be expressed as phenological events. The properties of the underlying mechanisms of the events in different seasons are further predicted, and the responses are compared with reported empirical examples. Because many organisms have evolved under the phase lag between photoperiod and temperature, the developmental plasticity in response to the phase lag should be evaluated for diverse organisms.     

Organogenesis in pepper tissue cultures

Knowledge concerning in vitro growth and developmental responses of bell and chile peppers (Capsicum annuum L.) has been limited. Shoot and root organogenesis in cultures of seedling explants was restricted to primary cultures or those less than three months old under 12-and 16-h photoperiod at 25°C. Shoot organogenesis was extended to 5 months under continuous light at 25°C, and to 8 months under continuous light at 28.5°C. Murashige and Skoog basal media containing 0.05mg/l each of IAA and BA promoted shoot elongation and rooting of some explant sources, while 0.05-4 mg/l IAA with 10–50 mg/l BA promoted adventitious shoot bud formation. Glucose was superior to sucrose as the carbon source. Leaf discs collected from greenhouse-grown plants regenerated shoots for at least 2 months. Incubation environment, carbon source, explant source, growth regulator treatment and passage number were not independent variables as demonstrated by statistical analysis. The plant regeneration techniques described here have useful but limited applications, not extending to unorganized callus or cell suspension cultures.Journal article no. 1151 of the New Mexico Agricultural Experiment Station.     

Light effects on development of an indeterminate plant

The peanut (Arachis hypogaea L.) plant is indeterminate in growth habit and day-neutral with respect to flower initiation. The Spanish-type cultivar used in this study begins flowering 3 to 4 weeks from planting under optimum environmental conditions. In this study, irradiance and photoperiod were used to alter the development of the peanut plant. Plants grown at low irradiance (300 microeinsteins per square meter per second) had the same number of leaves as the plants grown at high irradiance (500 microeinsteins per square meter per second), but they had a larger leaf surface area and were taller than plants grown at the high irradiance. However, flowering and other reproductive components (pegs, pods, and seeds) were reduced at low irradiance. Comparison of 8-, 12-, and 16-hour photoperiods at the high irradiance showed that the 16-hour photoperiod produced the largest amount of vegetative, but least amount of reproductive components. The plants grown at 8-hour photoperiod had one-third as much total leaflet area as plants grown at 16 hours, but six times more weight of mature seeds. The larger amount of photosynthetic surface (leaf area) did not result in more reproductive growth. The results indicate that the peanut plant may readily redistribute its available assimilates between vegetative and reproductive growth in response to irradiance and photoperiod.