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Photoperiod-dependent flowering in rice is regulated by HEADING DATE 1 (Hd1), which acts as both an activator and repressor of flowering in a daylength-dependent manner. To investigate the use of microProteins as a tool to modify rice sensitivity to the photoperiod, we designed a synthetic Hd1 microProtein (Hd1miP) capable of interacting with Hd1 protein, and overexpressed it in rice. Transgenic OX-Hd1miP plants flowered significantly earlier than wild type plants when grown in non-inductive long day conditions. Our results show the potential of microProteins to serve as powerful tools for modulating crop traits and unraveling protein function.

Plants sense light and temperature changes to regulate flowering time. Here, we show that expression of the Arabidopsis florigen gene, FLOWERING LOCUS T (FT), peaks in the morning during spring, a different pattern than we observe in the laboratory. Providing our laboratory growth conditions with a red/far-red light ratio similar to open-field conditions and daily temperature oscillation is sufficient to mimic the FT expression and flowering time in natural long days. Under the adjusted growth conditions, key light signalling components, such as phytochrome A and EARLY FLOWERING 3, play important roles in morning FT expression. These conditions stabilize CONSTANS protein, a major FT activator, in the morning, which is probably a critical mechanism for photoperiodic flowering in nature. Refining the parameters of our standard growth conditions to more precisely mimic plant responses in nature can provide a powerful method for improving our understanding of seasonal response.

The goal of this study was to determine whether the application of gibberellic acid (GA3) to seeds of common wheat varieties with different vernalization and photoperiod requirements affects the transition from vegetative to generative stage. Three varieties of wheat with different photoperiod sensitivities and vernalization were selected for the experiment&mdash, the winter varieties, Mironovskaya and Bezostaya, and the spring variety, Sirael. Seeds were treated with different concentrations of GA3 and plants were grown under long-day conditions with monitoring of their photosynthetic activity (Fv/Fm, Pn, E, gs). We monitored the activity of the photosynthetic apparatus by checking the plants to see if they were growing properly. The phenological stages of the wheat species were checked for indications of a transition from the vegetative to the generative stage. Selected concentrations of GA3 had no effect on the compensation of the vernalization process (transition to the generative phase). Chlorophyll fluorescence was one of the factors for monitoring stress. The variety, Bezostaya, is similar to the spring variety, Sirael, in its trends and values. The growth conditions of Bezostaya and Sirael were not affected by the activity of the photosynthetic apparatus. The development of growing points in winter varieties occurred at the prolonged single ridge stage. The spring variety reached the stage of head emergence after sixty days of growth (changes to the flowering phase did not appear in winter wheat). Application of GA3 to the seeds had no effect on the transition of the growing point to the double-ridge generative stage. The present study highlights the priming effect of GA3 on seeds of common wheat varieties with different vernalization and photoperiod requirements as it affected the transition from vegetative to generative stage.

Long days repeatedly enhance the expression of the FLOWERING LOCUS T (FT) gene during the evening and early night. This signal induces flowering despite low FT expression the rest of the day. To investigate whether this temporal behaviour transmits information, plants of Arabidopsis thaliana were exposed to different day–night cycles, including combinations that induced FT expression out of normal hours. Flowering time best correlated with the integral of FT expression over several days, corrected for a higher evening and early night sensitivity to FT. We generated a system to induce FT expression in a leaf removed 8–12 h later. The expression of flowering genes in the apex and flowering required cycles of induction repeated over several days. Evening and early night FT induction was the most effective. The temporal pattern of FT expression encodes information that discriminates long days from other inputs. Fil: Krzymuski, Martin Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Andrés, Fernando. Max Planck Institute for Plant Breeding Research; Alemania Fil: Cagnola, Juan Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina Fil: Jang, Seonghoe. Max Planck Institute for Plant Breeding Research; Alemania Fil: Yanovsky, Marcelo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentina Fil: Coupland, George. Max Planck Institute for Plant Breeding Research; Alemania Fil: Casal, Jorge Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Fundación Instituto Leloir; Argentina

The flowering responses of two Australian native Asteraceae species, Rhodanthe floribunda and Pycnosorus thompsonianus, to photoperiod and temperature were investigated to facilitate the manipulation of floral initiation and development. Plants were grown at 20/10 °C or 30/20 °C (day/night) under short day (SD: 11 h light) or long day (LD: 16 h light) in environment-controlled greenhouse bays in 2009 and 2010. LD advanced flowering by about 15 days and anthesis by 13 days in R. floribunda, and by 12 days and 15 days, respectively, in P. thompsonianus. Rhodanthe floribunda grown under cool temperatures (20/10 °C) produced 30% more inflorescences than the plants grown under warm temperatures (30/20 °C). Pycnosorus thompsonianus under LD produced more than double the number of inflorescences per plant than under SD (79.8 vs 33.7) regardless of temperature regimes. Both species are facultative LD plants. This knowledge is useful to regulate flowering of these ornamental plant species for potential commerciali...

Soybean ( Glycine max (L.) Merr.) is a typical short-day and warm season plant, and the interval between emergence and flowering has long been known to be regulated by environmental factors, primarily photoperiod and temperature. While the effects of photoperiod and temperature on soybean flowering have been extensively studied, a dissection of the component photo-thermal effects has not been documented for Chinese germplasm. Our objective of the current study was to evaluate the independent- and interactive-photo-thermal responses of 71 cultivars from 6 ecotypes spanning the soybean production regions in China. These cultivars were subjected in pot experiments to different temperature regimes by planting in spring (low temperature (LT)) and summer (high temperature (HT)), and integrating with short day (SD, 12 h), natural day (ND, variable day-length), and long day (LD, 16 h) treatments over two years. The duration of the vegetative phase from emergence to first bloom (R 1 ) was recorded, and the photo-thermal response was calculated. The outcome of this characterization led to the following conclusions: (1) There were significant differences in photo-thermal response among the different ecotypes. High-latitude ecotypes were less sensitive to the independent- and interactive-photo-thermal effects than low-latitude ecotypes; and (2) there was an interaction between photoperiod and temperature, with the effect of photoperiod on thermal sensitivity being greater under the LD than the SD condition, and with the effect of temperature on photoperiodic sensitivity being greater under the LT than the HT condition. The strengths and limitations of this study are discussed in terms of implications for current knowledge and future research directions. The study provides better understanding of photo-thermal effects on flowering in soybean genotypes from different ecotypes throughout China and of the implications for their adaptation more broadly.

The influence of light intensity and daylength on four short-day species of Chenopodium was analysed. The following species were tested: Ch. ficifolium, Ch. glaucum, Ch. rubrum and Ch. hybridum. Under short day, generative initiation was accelerated, the abundance of flowering, and growth and leaf differentiation processes were reduced. Under light of low intensity, the rhythm of development of the plants growing under long day is similar to that under short day. The development of axillary buds indicates a decrease in the intensity of vegetative differentiation and elongation growth, with an enhancement of the generative tonus; the buds in the axils of the highest growing leaves form directly inflorescences without preceding leaf differentiation. Inversion of the shape of leaves on lateral shoots was noted.

The effect of photoperiod (day:night ratio) on flowering time was investigated in the wild species, Setaria viridis, and in a set of recombinant inbred lines (RILs) derived from a cross between foxtail millet (Setaria italica) and its wild ancestor green foxtail (S. viridis). Photoperiods totaled 24 hours, with three trials of 8:16, 12:12 and 16:8 light:dark hour regimes for the RIL population, and these plus 10:14 and 14:10 for the experiments with S. viridis. The response of S. viridis to light intensity as well as photoperiod was assessed by duplicating photoperiods at two light intensities (300 and 600 mol.m-2.s-1). In general, day lengths longer than 12 hours delayed flowering time, although flowering time was also delayed in shorter day-lengths relative to the 12 hour trial, even when daily flux in high intensity conditions exceeded that of the low intensity 12 hour trial. Cluster analysis showed that the effect of photoperiod on flowering time differed between sets of RILs, with some being almost photoperiod insensitive and others being delayed with respect to the population as a whole in either short (8 or 12 hours light) or long (16 hours light) photoperiods. QTL results reveal a similar picture, with several major QTL colocalizing between the 8 and 12 hour light trials, but with a partially different set of QTL identified in the 16 hour trial. Major candidate genes for these QTL include several members of the PEBP protein family that includes Flowering Locus T (FT) homologs such as OsHd3a, OsRFT1, and ZCN8/12. Thus, Setaria is a short day plant (flowering quickest in short day conditions) whose flowering is delayed by long day lengths in a manner consistent with the short-day response of other members of the grass family. However, the QTL results suggest that flowering time under long day conditions uses additional genetic pathways to those used under short day conditions.

Seedlings of the medicinal plant Hyoscyamus albus were supplied with an excess of Cu to examine the possible application in phytoremediation. The seedlings were cultured in B5 medium supplied with basal 0.1 μM Cu and 200 μM Cu under various light conditions: short day (SD); long day (LD); and continuous light (CL). In addition, the effect of supplying 200 μM Cu under Fe deficiency was determined, in order to elucidate the interaction between Cu and Fe. Interestingly, Fe-deficiency symptoms that developed in plants grown with basic levels of Cu under LD almost disappeared when excess Cu was supplied. Plant growth mainly depended on the photo irradiation period (SD < LD~CL); and 200 μM Cu did not inhibit growth at all when Fe was available, whereas in the absence of Fe, CL caused damage to growth. Analysis of the Cu and Fe contents of the plants revealed that Cu was distributed equally in both the aerial parts and roots, whereas most of the Fe was found in the roots; under Fe deficiency, Cu accumulation in the roots apparently increased. Cu was mainly distributed in the soluble fraction, which included vacuoles and the cell-wall fraction. These results provide evidence indicating that H. albus seedlings are tolerant of Cu present in excess. Furthermore, excess Cu was able to compensate for Fe deficiency, depending on the light conditions. Continuous light inhibited this effect, probably as a result of the induction of Mn deficiency. The possible applications of this newly discovered cuprophyte are discussed., American Journal of Plant Sciences, 5(26), pp.3812-3822; 2014

Stress-associated protein (SAP) has functions in maintaining plant cell elongation, embryo development and response to abiotic stresses. TaSAP1-A1 , one of the Triticum aestivum SAP1 ( TaSAP1 ) members located on wheat chromosome 7A was isolated for polymorphism analysis. Hap III of TaSAP1-A1 was found significantly associated with thousand-grain weight (TGW) in multiple environments. In this study, Hap III also made a positive contribution to TGW in Population 2. The distribution of TaSAP1-A1 Hap III was tracked among varieties released in different years and geographical environments of China. The frequency of Hap III showed an increasing trend during the breeding process in two different populations. The Hap III was gradually selected and applied from 6.36% in landraces to 13.50% in modern varieties. These results exhibited that TaSAP1-A1 Hap III was positively selected during wheat breeding, which is beneficial for grain-yield improvement. The preferred Hap III was initially selected and applied in the higher latitude areas of China in accord with the long day season and longer grain filling stage in these areas. Moreover, the frequency of Hap III in recent modern varieties was still quite low (19.29–26.67%). It indicated a high application potential of TaSAP1-A1 Hap III for improving grain yield in wheat breeding.

The ability of two Trichogramma species (Trichogramma telengai Sor. and T. principium Sug. et Sor.) to accumulate the effect of the maternal photoperiodic response during 5 consecutive generations reared in the laboratory under the short day (12 h) conditions was investigated. Control individuals developed at the same temperature of 20°C, but under the long day (18 h) conditions. The tendency to diapause was estimated by the proportion of progeny that entered diapause under the short day conditions at the temperatures of 13, 14 and 15°C. Trichogramma principium manifested an evident transgenerational cumulative photoperiodic response: the development of 1, 2, and 3 consecutive generations under the short day conditions caused a gradual increase in the proportion of diapausing progeny. In T. telengai, the progeny of the females that developed under the short day conditions also entered diapause more often than the progeny of those that developed under the long day conditions, but the number of preceding generations which developed under short day had no effect on the tendency to diapause. This interspecific difference can be possibly explained by the different natural geographic ranges of the two studied species. Trichogramma principium occurs in Southern Europe, Southern Kazakhstan, and Central Asia where the autumnal decrease in temperature is very slow and thus two or even more generations can develop under the short day conditions, whereas T. telengai is distributed over Central and North-Western Europe and in Siberia, where the autumnal decrease in temperature is rather fast, the development of one more “autumnal” generation is risky, and thus even the first “short-day signal” induces a very strong tendency of the progeny to diapause.

SummaryWhen maintained continuously under long-day (non-inductive) photoperiodic conditions, chrysanthemum (Chrysanthemum morifolium Ramat.), a short-day plant, eventually initiates flower buds. This floral initiation is termed ‘premature budding’ in commercial chrysanthemum production. Premature budding, which reduces cut-flower quality, is often observed in summer-to-autumn-flowering cultivars. The timing of flower initiation under non-inductive photoperiods depends on the number of leaves that a plant has formed below the terminal flower bud. This leaf number indicates whether a cultivar will form flower buds prematurely during a non-inductive photoperiod. Two summer-flowering, ten summer-to-autumn-flowering, and six autumn-flowering chrysanthemum cultivars were grown under controlled conditions to measure the number of leaves produced under a non-inductive photoperiod with a night-break. The average number of leaves per plant ranged from 13.8 for ‘Tasogare’, to 69.1 for ‘Furamu’. These data can be use...

Marked differences were found between the photoperiodic responses of Bryophyllum daigremontianum and Bryophyllum tubiflorum, both species being classified as long-short-day plants (LSDP). The flowering of B. daigremontianum was observed under several photoperiodic conditions, among others under continuous exposure to long day (LD) or after transferring plants from a short-day (SD) to a long-day exposure: both conditions were regarded previously as non-inductive. It is argued that the flowering of B. daigremontianum is conditioned by sufficiently long LD exposure followed by one of two factors: the shortening of the day or the lowering of the temperature. The flowering of B. tubiflorum was observed only under more specific photoperiadic conditions, it seems to be conditioned by several successive changes of the length of the photoperiod.

This study was investigation for primary bionomical characteristics, emergence rate of wintering type pupa and oviposition preference, of Papilio xuthus. The emergence rate of wintering type pupa stored at cold chamber() was 85%, after 10 months. The average emergence rate of wintering type pupa during storage was 89.6%, and the emergence periods were in room temperature. Mating ratio in large oviposition room, mm(), was higher than in small room, mm(). But the number of eggs in the large room were fewer than in the small room. As a result of oviposition preference experiment on three different host plants, 10 mated female laid on the leaves of Phellodendron amurensew more than on Zanthoxylum schinifolium and on Citrus unshiu. The egg periods were days after oviposition, and the hatchability was 92.2% in room condition. The larval period were days in the high temperature, long day condition(, 14L : 10D). The headwidth of each developmental larval stage were (1st), (2nd), (3rd), (4th), (5th). The pupal ratio was 91.6%. The pupal period were days, and the emergence rate was 92.2%.

Photoperiod is one of the major environmental factors determining time to flower initiation and first flower appearance in plants. In chickpea, photoperiod sensitivity, expressed as delayed to flower under short days as compared to long days, may change with the growth stage of the crop. Photoperiod sensitive and insensitive phases were identified by experiments in which individual plants were reciprocally transferred in a time series from long to short days and vice versa in growth chambers. Eight chickpea accessions with differing degrees of photoperiod sensitivity were grown in two separate chambers, one of which was adjusted to long days (16 hours light/8 hours dark) and the other adjusted to short days (10 hours light/14 hours dark), with temperatures of 22/16 ºC (12 hours light/12 hours dark) in both chambers. The accessions included day-neutral (ICCV 96029 and FLIP 98-142C), intermediate (ICC 15294, ICC 8621, ILC 1687, and ICC 8855), and photoperiod sensitive (CDC Corinne and CDC Frontier) responses. Control plants were grown continuously under the respective photoperiods. Reciprocal transfers of plants between the short and long day photoperiod treatments were made at seven time points after sowing, customized for each accession based on previous data. Photoperiod sensitivity was detected in intermediate and photoperiod sensitive accessions. For the day-neutral accession, ICCV 96029, there was no significant difference in the number of days to flowering of the plants grown under short days and long days as well as subsequent transfers. In photoperiod sensitive accessions, three different phenological phases were identified: a photoperiod insensitive pre-inductive phase, a photoperiod-sensitive inductive phase, and a photoperiod-insensitive post-inductive phase. The photoperiod sensitive phase extends after flower initiation to full flower development. Results from this research will help to develop cultivars with shorter pre-inductive photoperiod insensitive and photoperiod sensitive phases to fit to regions with short growing seasons.

The photoperiod sensitivity gene Ppd-1 influences the timing of flowering in temperate cereals such as wheat and barley. The effect of Ppd-1 on the expression of flowering-time genes was assessed by examining the expression levels of the vernalization genes VRN1 and VRN3/WFT and of two CONSTANS-like genes, WCO1 and TaHd1, during vegetative and reproductive growth stages. Two near-isogenic lines (NILs) were used: the first carried a photoperiod-insensitive allele of Ppd-1 (Ppd-1a-NIL), the other, a photoperiod-sensitive allele (Ppd-1b-NIL). We found that the expression pattern of VRN1 was similar in Ppd-1a-NIL and Ppd-1b-NIL plants, suggesting that VRN1 is not regulated by Ppd-1. Under long day conditions, VRN3/WFT showed similar expression patterns in Ppd-1a-NIL and Ppd-1b-NIL plants. However, expression differed greatly under short day conditions: VRN3/WFT expression was detected in Ppd-1a-NIL plants at the 5-leaf stage when they transited from vegetative to reproductive growth; very low expression was present in Ppd-1b-NIL throughout all growth stages. Thus, the Ppd-1b allele acts to down-regulate VRN3/WFT under short day conditions. WCO1 showed high levels of expression at the vegetative stage, which decreased during the phase transition and reproductive growth stages in both Ppd-1a-NIL and Ppd-1b-NIL plants under short day conditions. By contrast to WCO1, TaHd1 was up-regulated during the reproductive stage. The level of TaHd1 expression was much higher in Ppd-1a-NIL than the Ppd-1b-NIL plants, suggesting that the Ppd-1b allele down-regulates TaHd1 under short day conditions. The present study indicates that down-regulation of VRN3/WFT together with TaHd1 is the cause of late flowering in the Ppd-1b-NIL plants under short day conditions.

Summer dormancy enables tall fescue (Festuca arundinacea Schreb.) to survive hot and dry summers. Phenotyping summer dormancy in the fi eld can be problematic owing to the confounding effects of heat and drought. The objective therefore was to develop a method for phenotyping summer dormancy in tall fescue. Three genotypes (summer active [SA], moderately summer dormant [MSD], and strongly summer dormant [SSD]) were grown in four growth chambers under long day (LD) and high temperature (HT), LD and optimum temperature (OT), short day (SD) and HT, and SD and OT conditions. Within each chamber, two levels of moisture (well watered [+W] or drought [–W]) and vernalization (vernalized [+V] or nonvernalized [–V]) were also tested. Under SD, OT, +W, and +V conditions, SSD had equal or greater growth compared to SA genotype, as measured by number of tillers, plant height, fresh weight, and dry weight. The SSD genotype grew less than the SA as measured by number of tillers (8.6 vs. 15.8), fresh weight (6.0 vs. 16.0 g), and dry weight (3.1 vs. 8.8 g) under LD, OT, +W, and +V conditions. The MSD genotype had intermediate responses. Plant height of genotypes followed a similar pattern during two consecutive regrowth periods. Dormancy of plants could not be classifi ed under drought or without prior vernalization. Dormancy of genotypes could be differentiated by comparing growth under favorable (SD, OT, +W, and +V) versus LD, OT, +W, and +V conditions.

While low intensity long-day (LD) lighting has been shown to enhance the growth of young plants under low light levels, its effect on the yield of a long-season glasshouse tomato crop has not been previously examined. LD were provided by the use of tungsten lamps (2.8 μmol m-2 s-1 at approx. 0.5 m from the ground) between 04.00 h to sunrise and from sunset until 20.00 h (GMT). LD lighting increased leaf chlorophyll contents, and the numbers of flowers and fruits set per truss when the plants were young. However, this treatment did not affect the total yield of tomatoes. Different leaf removal treatments were applied within each glasshouse compartment. A previous experiment had shown that reducing the leaf area index (LAI) from 5.2 to 2.6, by removing old leaves, did not affect yield. It was also thought that removal of young leaves reduced the total vegetative sink-strength and favoured assimilate partitioning into the fruit. Therefore, removal of young leaves could increase fruit yield. In the present experiments, one-third of the leaves were removed in March (those immediately below each truss) and, subsequently, every third leaf was removed at an early stage of its development. This reduced the LAI from 4.1 to 2.9 and resulted in a loss of yield from 3 – 4 weeks after leaf removal until the end of the experiment, at which point there was an 8% loss of cumulative yield due to a reduction in the average number of fruits set per truss and in mean fruit weight. We postulate that the light which would have been intercepted by young photosynthetically-efficient leaves at the top of the canopy was intercepted instead by older leaves which were less efficient, reducing overall net canopy photosynthesis.

The responses of dormancy induction to illumination and the characteristics of respiratory rate were studied with the nectarine peach bud in this article. The trial was conducted with nectarine (Prunus persica var. nectariana cv. Shuguang) and involved three treatments: a short day treatment (8 h), a long day treatment (16 h), and the normal condition as the control. The dormancy status was determined with the growth of shoot and the sprouting ability, and the respiratory rate was mensurated with oxygen electrode. Short day treatment could induce the growth stopping of peach shoots ahead, promote the development of dormancy, and induce buds into dormancy with 21 d previous to control. Long day treatment postponed the growth stopping and the induction and development of dormancy. The respiratory rate decreased according to the development of dormancy induction. The minimum respiratory rate appeared about 7 days after the start of dormancy induction. Bud respiratory rate increased during this period and then declined and remained at low level during dormancy period. Long day reduced buds respiratory rate slightly. Short day could induce dormancy obviously, and long day postponed dormancy induction. The changes of respiratory rate were correlated with the development of dormancy induction, and the bud respiratory rate was also affected by photoperiod.

Arabidopsis flowers in long day (LD) in response to signals transported from the photoinduced leaf to the shoot apex. These LD signals may include protein of the gene FLOWERING LOCUS T (FT) while in short day (SD) with its slower flowering, signalling may involve sucrose and gibberellin. Here, it is shown that after 5 weeks growth in SD, a single LD up-regulated leaf blade expression of FT and CONSTANS (CO) within 4-8 h, and flowers were visible within 2-3 weeks. Plants kept in SDs were still vegetative 7 weeks later. This LD response was blocked in ft-1 and a co mutant. Exposure to different LD light intensities and spectral qualities showed that two LD photoresponses are important for up-regulation of FT and for flowering. Phytochrome is effective at a low intensity from far-red (FR)-rich incandescent lamps. Independently, photosynthesis is active in an LD at a high intensity from red (R)-rich fluorescent lamps. The photosynthetic role of a single high light LD is demonstrated here by the blocking of the flowering and FT increase on removal of atmospheric CO(2) or by decreasing the LD light intensity by 10-fold. These conditions also reduced leaf blade sucrose content and photosynthetic gene expression. An SD light integral matching that in a single LD was not effective for flowering, although there was reasonable FT-independent flowering after 12 SD at high light. While a single photosynthetic LD strongly amplified FT expression, the ability to respond to the LD required an additional but unidentified photoresponse. The implications of these findings for studies with mutants and for flowering in natural conditions are discussed.

This study aimed to clarify the flowering habit in sorghum varieties with a dominant thermosensitivity gene. The number of days from sowing to floral initiation in four varieties with a dominant thermosensitivity gene (TT and Tt) and two varieties of which flower initiation does not depend strongly on day-length and night temperatures were evaluated under different day-length and temperature conditions. The day-length treatment at 25°C indicated that anything over a 12.5-h day-length has a long day effect on the flowering of the sorghum varieties examined. Under a long day condition of a 12.5-h day-length, floral initiation was accelerated under 30°C/20°C (day/night) conditions, compared to 25°C (constant) conditions in the varieties with a dominant thermosensitivity gene. Under a 15-h day-length, floral initiation was accelerated at night temperatures of 20°C and 15°C instead of at the constant 25°C. These results suggest that floral initiation was accelerated by a night temperature of lower than 20°C, even under long day-length conditions in sorghum varieties with a dominant thermosensitivity gene.

SummaryThe environmental control of flowering in the perpetual-flowering (everbearing) diploid strawberry Fragaria vesca ssp. semperflorens cultivars ‘Rugen’ and ‘Baron Solemacher’ has been studied in controlled environments. Seedpropagated plants were exposed to 10-h short-day (SD) and 24-h long-day (LD) conditions at temperatures ranging from 9° – 27°C. The results revealed a quantitative LD response of flowering that increased in strength with increasing temperature, to become almost obligatory at 27°C. Occasional runner formation was observed in SD at high temperature, conditions which were inhibitory to flowering, demonstrating that runnering ability is not completely lost in these genotypes. A comparison with the perpetual-flowering octoploid F. ananassa ‘Elan’, in one experiment, demonstrated an identical LD temperature interaction in the two species. The results are discussed in relation to available information on the genetics of flowering habits in the two species. Since seasonal flowering types...

Floral induction and development requirements of a range of latitudinal and altitudinal Norwegian populations of the wild strawberry Fragaria vesca L. have been studied in controlled environments. Rooted runner plants were exposed to a range of photoperiods and temperatures for 5 weeks for floral induction and then transferred to long day (LD) at 20°C for flower development. A pronounced interaction of temperature and photoperiod was shown in the control of flowering. At 9°C, flowers were initiated in both short day (SD) and LD conditions, at 15 and 18°C in SD only, whereas no initiation took place at 21°C regardless of daylength conditions. The critical photoperiod for SD floral induction was about 16 h and 14 h at 15 and 18°C, respectively, the induction being incomplete at 18°C. The optimal condition for floral induction was SD at 15°C. A mini mum of 4 weeks of exposure to such optimal conditions was required. Although the populations varied significantly in their flowering performance, no clinal relationship was present between latitude of origin and critical photoperiod. Flower development of SD-induced plants was only marginally advanced by LD conditions, while inflorescence elongation and runnering were strongly enhanced by LD at this stage. The main shift in these responses took place at photoperiods between 16 and 17 h. Unlike all other populations studied, a high-latitude population from 70°N ('Alta') had an obligatory vernalization requirement. Although flowering and fruiting in its native Subarctic environment and after overwintering in the field in south Norway, this population did not flower in the laboratory in the absence of vernalization, even with 10 or 15 weeks of exposure to SD at 9°C. Flowering performance in the field likewise indicated a vernalization requirement of this high-latitude population.

SummaryPerpetual-flowering strawberry cultivars are commonly classified as photoperiodically day-neutral, even though early investigations demonstrated long-day (LD) regulation. An important reason for this inconsistency is that these freely flowering plants are difficult to establish in a true vegetative state, and experiments have therefore often been started using runner plants with pre-formed inflorescences. In order to circumvent this problem, we have used the perpetual-flowering F1-hybrid ‘Elan’ that is propagated by seed, and is thus not pre-conditioned by its earlier life history. The results demonstrated a marked quantitative LD response across a range of temperatures from 9° – 27°C. Seedlings were responsive to the LD stimulus at an early stage, and early flowering required LD exposure almost from germination. The critical daylength for the early flowering response was about 15 h at 18°C. Because of this threshold LD response, it is concluded that regulation of flowering is truly photoperiodic i...

There have been several reports on the effects of various photoperiods on flowering in Capsicum annuum, but few on such effects on other species of the genus Capsicum. In this study, the flowering under various photoperiods of two C. frutescens lines from the Bonin and Ryukyu Islands in Japan and C. annuum cv. ‘Takanotsume’ (referred as BON, RYU, and TK, respectively) was investigated. The main differences in flowering between C. frutescens and C. annuum were evident under long-day photoperiods. TK plants grown under photoperiods longer than 15 h bore flowers normally, whereas BON and RYU plants grown under the same conditions did not bear flowers at first, because their buds failed to grow, and eventually aborted. BON plants bore flowers under a 24-h photoperiod, although the time to flowering was much longer than that for TK plants, but RYU plants exposed to photoperiods longer than 14 h bore no flowers during the entire experimental period. Therefore, long-day photoperiods strongly inhibit C. frutescens flower bud growth, and there are interspecific differences in flowering between C. frutescens and C. annuum and intraspecific differences in flowering between the two C. frutescens genotypes.

The rotation of our planet results in regular changes in environmental cues such as daylength and temperature, and organisms have evolved a molecular oscillator that allows them to anticipate these changes and adapt their development accordingly. In many plants, the transition from vegetative to reproductive growth is controlled by photoperiod, which synchronises flowering with favourable seasons of the year. Here, we describe the notable progress that has been made in identifying the molecular mechanisms that measure daylength and control of flowering time in Arabidopsis, a long day (LD) plant, and in rice, a short day (SD) plant. Although the components of the Arabidopsis regulatory network seem to be conserved in other species, the difference in the function of particular genes may contribute to the reverse response to daylength observed between LD and SD plants. We also highlight the recent advances in understanding the regulatory mechanisms that underlie other developmental transitions contr...

Results from hemp experiments in European countries indicate that long day conditions may be beneficial for the fibre content and quality of hemp. The long day conditions during summer in Sweden are therefore of interest. This paper presents results from the first fibre hemp experiments carried out in Sweden since the 1960s. Field trials were performed in southern Sweden, during the years 1999-2001, testing three monoecious varieties (Felina, Fedora and Futura) at seed rates of 30 and 60 kg/ha. Total biomass yield in autumn varied from 7.8 to 14.5 ton DM/ha and fibre yield from 1.9 to 3.3 ton DM/ha. The highest fibre yields per hectare were produced by the variety Futura, the lowest by Fedora. The seed rates 30 and 60 kg/ha gave similar biomass and fibre yields, but the plant density was lower and the stem diameter was larger at 30 kg/ha. Results of chemical analyses of stem and leaves are presented.

The influence of three photoperiods, viz. short day [8 : 16 h; light : dark (L : D)], long day (16 : 8 h; L : D) and continuous light (24 : 0 h; L : D) and four wavelengths of light, viz. white (control), yellow, blue and red on pre-imaginal development and reproductive performance of a ladybird, Coelophora (=Lemnia) saucia (Mulsant) (Col., Coccinellidae) have been investigated under laboratory conditions. Long-day photoperiod and white light resulted in low immature stage mortality. Total larval period was longest under short-day and red-light conditions. Females kept at long-day photoperiod and under white light showed better reproductive performance than those placed under other photoperiods and wavelengths.

Experiments were conducted in environmental chambers to the evaluate effects of photoperiod and temperature on Florida betony growth and development. Plants were exposed to two photoperiods, short day (9 h) and long day (9 + 3 h night interruption), and three day/night temperature regimes, 18/14, 22/18, and 26/22 C. After 10 wk of growth, shoot length and weight were 3.4 and 3.5 times greater, respectively, in the long-day photoperiod and with the 26 and 22 than with the 22 and 18 C day and night temperature regime, respectively. Shoot number, however, was greatest in the short-day photoperiod and at a lower temperature of 22/18 C. Shoot number in long day 22/18 C and 26/22 C environments increased asymptotically. No difference in root weight was observed between long- and short-day environments, but root weight increased with increasing temperature. Flowering and tuber production only occurred in long-day environments, with greater production of both at higher temperatures. Results provide a general framework for understanding Florida betony growth and development characteristics in the field and provide insights that should be considered in developing control strategies.

To gain an understanding of the adaptation of Australian and Canadian barley (Hordeum vulgare L.) cultivars to the environments of western Canada and Western Australia, phyllochron and number of leaves on the mainstem in eight cultivars of two-row, spring barley were examined when sown at two dates in two locations. The locations were a short-day environment at Northam, Western Australia, Australia in 1997 and a long-day environment at Lacombe, Alberta, Canada in 1998. At each location highly significant relationships between leaf number on the mainstem and thermal time were found (r2 > 0.94). Using linear estimates, the phyllochron of barley under short days was longer than under long days and was correlated to time to awn emergence. Later sowing shortened phyllochron under short days, but generally not under long days. Error messages from the linear regression analysis suggested that residuals were not random for all cultivars. Bilinear models were fitted to those datasets. Bilineal responses were observed under both short and long days, being independent of cultivar, date of seeding, final leaf number, phenological development pattern and time to awn emergence. The occurrence of a bilinear response was also independent of any ontogenetic events. The change in phyllochron occurred between leaves 4–7 at Northam and between leaves 6–9 at Lacombe. The leaf number at which the phyllochron change occurred was positively related to final leaf number and time to awn emergence. The phyllochron of early forming leaves was positively related to time to awn emergence and shorter than later forming leaves. Leaf emergence patterns in spring barley under both long-day and short-day conditions may therefore be linear or bilinear. Key words: barley (spring), Hordeum vulgare L., phyllochron, leaf emergence, daylength

Echinacea purpurea cv. Bravado and Magnus have been reported to be intermediate daylength plants (IDP) which flower in response to photoperiods between 13 and 16 h. The present experiments with E. purpurea cv. Bravado show that E. purpurea is actually a dual induction short-long-day plant which flowers promptly and consistently when grown in short day (SD) followed by long day (LD) conditions, but not with the reverse sequence of photoperiods. The flowering response increased with increasing duration of both the SD and the LD treatments. A minimum of 4 weeks of SD followed by 12 LD was required for complete flowering. No flowering occurred in continuous SD or LD, whereas a high proportion of plants flowered in continuous 14-h daylength. However, flowering was more variable in intermediate daylength than after transition from SD to LD. Furthermore, photoperiods between 13 and 16 h could satisfy both the primary SD induction and the secondary LD induction requirements. As a number of dual induction plants, both short-long-day and long-short-day plants, have such an overlapping window of effective photoperiods that can trigger both the SD and LD responses, the rationale for maintaining IDP as a separate and genuine flowering response group is seriously challenged.

Plastics that selectively reduce the transmission of far-red light (FR, 700 to 800 nm) reduce extension growth of many floricultural crops. However, FR-deficient (FRd) environments delay flowering in some long-day plants (LDPs), including `Crystal Bowl Yellow' pansy (Viola ×wittrockiana Gams). Our objective was to determine if FR light could be added to an otherwise FRd environment to facilitate flowering with minimal extension growth. In one experiment, plants were grown under a 16-hour FRd photoperiod, and FR-rich light was added during portions of the day or night. For comparison, plants were also grown with a 9-hour photoperiod [short-day (SD) control] or under a neutral (N) filter with a 16-hour photoperiod (long day control). Flowering was promoted most (i.e., percent of plants that flowered increased and time to flower decreased) when FR-rich light was added during the entire 16-hour photoperiod, during the last 4 hours of the photoperiod, or during the first or second 4 hours after the end of the photoperiod. In a separate experiment, pansy was grown under an FRd or N filter with a 9-hour photoperiod plus 0, 0.5, 1, 2, or 4 hours of night interruption (NI) lighting that delivered a red (R, 600 to 700 nm) to FR ratio of 0.56 (low), 1.28 (moderate), or 7.29 (high). Under the N filter, the minimum NI duration that increased percent flowering was 2 hours with a moderate or low R:FR and 4 hours with a high R:FR. Under the FRd filter, 2 or 4 hours of NI lighting with a moderate or low R:FR, respectively, was required to increase percent flowering, but a 4-hour NI with a high R:FR failed to promote flowering. Pansy appears to be day-neutral with respect to flower initiation and a quantitative LDP with respect to flower development. The promotion of reproductive development was related linearly to the promotion of extension growth. Therefore, it appears that in LDPs such as pansy, light duration and quality concomitantly promote extension growth and flowering, and cannot readily be separated with lighting strategies.

Bulbing response of Allium × wakegi Araki cv. Kiharabansei No.1 to temperature prior to bulb formation was investigated. The plants exposed to 5°C for 35 days were grown at 20°C under photoperiods ranging from 11 to 14 hrs. The control plants were kept above 15°C before the photoperiodic treatment. Regardless of the exposure to low temperature, the plants did not form bulbs under 11- and 12-hr photoperiods, whereas they did under a 14-hr photoperiod. Under 13- and 14-hr photoperiods, the plants exposed to low temperature had higher bulbing ratios (the maximum diameter of basal leaf sheath/the minimum neck diameter) and higher percentages of tillers with bulb scales (bladeless swollen leaves) than had the control plants. Low temperature exposure did not induce bulb formation of A. × wakegi, but shortened the critical photoperiod for bulb formation from 14 hrs to 13 hrs. When bulbs were stored between 1 and 25°C for 50 days and grown at 20°C under a 13-hr photoperiod, storage at or below 15°C promoted the formation of new bulbs. Storage at 10°C was more effective than that at 15°C, but below 10°C, it exerted no additional effect. When bulbs were stored at 5°C between 0 and 84 days and grown at 20°C under a 13-hr photoperiod, the formation of new bulbs was promoted as the cold storage period was extended. The promotive effect of low temperature on bulb formation was weakened by subsequent exposure to 25-35°C.

Production of high quality seed potatoes is normally favoured by a cool climate with minor pest problems. Growth chamber studies aimed to reveal if daylengths (12 and 24 hrs) and temperatures (18/12 and 12/9°C day/night) during production also might influence progeny growth. Results showed no significant carry-over effect from daylength conditions, while growth vigour and yields were affected by parent plant growth temperature. Further experiments, including a greater range of temperatures, different cultivars and measurements of physiological age, are required to discuss theoretical and practical implications of the results.

This study was conducted to determine the duration of exposure to low temperature required to induce bolting of rosetted seedlings and subsequent emergence of lateral buds in Elatum hybrids of Delphinium. When seedlings of 'Blue Springs', which rosettes from autumn to winter, were exposed to natural low temperature until December 5 or 15, plants bolted earlier under long days after being transferred to the greenhouse kept above 10°C than those under natural day length. This result means that exposure to low night temperature below 7°C for 30 days was required to induce bolting of rosetted seedlings, whereas the long day treatment after heating hastened flowering. Lateral buds on the base of main stems were induced to elongate and bolt when plants were exposed to 5°C at night for 30 days after cutting back the main stems in 'Blue Springs' and 'Magic Fountains Sky Blue'. When they were grown above 10°C, they produced 2.1-2.2 inflorescences/plant which flowered 70-74 days after heating. Lateral buds on the base of secondary shoots emerged without rosetting after secondary flowers were harvested in early April and flowered about 2 months later.

Plant development between seedling\ud emergence and flowering is characterized\ud by a series of successive qualitative\ud phases: (1) a post embryonic photoperiodinsensitive\ud phase, during which plants are\ud insensitive to photoperiod; (2) a photoperiod-\ud sensitive inductive phase, in which\ud plants require a number of short day\ud (SD) or long day (LD) inductive cycles,\ud depending on their age for rapid flowering,\ud and (3) a photoperiod-insensitive\ud post-inductive phase, in which plant\ud development is no longer influenced by\ud photoperiod (Figure 1; Matsoukas et al.,\ud 2013).\ud

Young seedlings of the conifer Norway spruce exhibit short day (SD)-induced cessation of apical growth and bud set. Although different, constant temperatures under SD are known to modulate timing of bud set and depth of dormancy with development of deeper dormancy under higher compared to lower temperature, systematic studies of effects of alternating day (DT) and night temperatures (NT) are limited. To shed light on this, seedlings of different provenances of Norway spruce were exposed to a wide range of DT-NT combinations during bud development, followed by transfer to forcing conditions of long days (LD) and 18°C, directly or after different periods of chilling. Although no specific effect of alternating DT/NT was found, the results demonstrate that the effects of DT under SD on bud set and subsequent bud break are significantly modified by NT in a complex way. The effects on bud break persisted after chilling. Since time to bud set correlated with the daily mean temperature under SD at DTs of 18 and 21°C, but not a DT of 15°C, time to bud set apparently also depend on the specific DT, implying that the effect of NT depends on the actual DT. Although higher temperature under SD generally results in later bud break after transfer to forcing conditions, the fastest bud flush was observed at intermediate NTs. This might be due to a bud break-hastening chilling effect of intermediate compared to higher temperatures, and delayed bud development to a stage where bud burst can occur, under lower temperatures. Also, time to bud burst in un-chilled seedlings decreased with increasing SD-duration, suggesting that bud development must reach a certain stage before the processes leading to bud burst are initiated. The present results also indicate that low temperature during bud development had a larger effect on the most southern compared to the most northern provenance studied. Decreasing time to bud burst was observed with increasing northern latitude of origin in un-chilled as well as chilled plants. In conclusion, being a highly temperature-dependent process, bud development is strongly delayed by low temperature, and the effects of DT is significantly modified by NT in a complex manner.

A Polysiphonia-type life history was demonstrated for Dasya caraibica in culture. Plants initially developed as monosiphonous filaments. Cellulosympodial branching was initiated after 5 days and pericentral cells were first cut off after 11–13 days. Pericentral cell initiation occurred immediately behind the apex and proceeded acropetally until the entire plant was polysiphonous. Rhizoidal cortication only developed with reproductive maturity, within 3–4 weeks. Spermatangia developed before procarps, the latter forming only under long day (16:8 h light: dark) conditions. A virtually identical pattern of gametophyte morphological development was also observed for Heterosiphonia crispella.

A new protein in the leaves of NK58S and NK58 (Oryza sativa L. subsp.japonica), which can be induced by 10 d-long-day photoperiod (14 h lightid) and cannot be induced by 10 d-short-day photoperiod (10 h light/d), has been found by two-dimensional gel electrophoresis. The protein, whose molecular weight and isoelectric point are 36 ku and pH 5.2 respectively, is found to be controlled by phytochrome as shown by the experiment of red light induction-far red light reversion.The existence of this protein in both NK58S and NK58 reflects that some of the responses of NK58S and NK58 might be similar in response to long-day photoperiod, a mild stress.

Long-day-adaptedSolanum phureja clones were assessed for resistance to blackleg caused byErwinia carotovora subsp.atroseptica under field and controlled environmental conditions over two years. In the field, twenty-two of the twenty-three clones ofS. phureja assessed were as resistant to blackleg as the commercial cultivar Ailsa, the most resistant control, and were significantly (P

The effect of long-day treatment with five lamps of different spectral characteristics on shoot growth of one-year-old own-rooted 'Pione' grapevines was investigated. Photon flux density (PFD) in each wavelength of physiologically active radiation (300-800 nm), red light (R, 600-700 nm), and far-red light (FR, 700-800 nm) emitted from the following five lamps : silica, blue-light, white-light, homolux (for plant growing) and red-light were determined. All lamps were lit just before sunset and daylength was prolonged to 16 hr for 11 weeks as from mid- August. Shoot elongation, number of nodes and leaf area per shoot, were significantly larger in vines exposed to lamps of homolux, red-light and silica as compared to the control vines, which were grown under natural daylength. Shoot growth of vines exposed to the white-light lamp was intermediate between those exposed to homolux and natural daylength, whereas in vines exposed to the blue-light lamp grew almost as well as the control vines. PFD (μmol·m-2·s-1) within the wavelength of red light of homolux, red-light and silica lamps were 0.157, 0.506 and 0.703, respectively. Nevertheless, these 3 lamps promoted shoot growth. PFD of red light emitted from the white-light and homolux lamps was almost the same, but white-light lamp had no peak at 660nm. R/FR (600-700 nm/700-800 nm) photon flux ratios also differed among the lamps, ranging from 0.50 to 19.46. Based on the results, the relationship between shoot growth of grapevines and spectral characteristics of each lamp is discussed in Japanese.

Adult emergence in Coleophora alticolella held at 15 °C was accelerated by exposure to L18:D6 in autumn and midwinter. The effect decreased during winter and exposure of individuals, held at low temperature over winter, to L18:D6 or L6:D18 at 15 °C at the end of March resulted in the same mean emergence date. Long daylength experienced at 5 °C did not promote emergence nor did exposure to low temperature during winter. The number of adults emerging increased with the length of time cultures were held on short day but was always below 50% of the larvae. When larvae were exposed to L18:D6 and L6:D18 at 15 °C at the end of March, on long day 61% adults emerged and 39% remained in diapause, whereas on short day, 25% became adult and 75% remained diapausing larvae. The possibility of cohort splitting, with some individuals undergoing prolonged diapause, is discussed.