Nucleotide diversity at two phytochrome loci along a latitudinal cline in Pinus sylvestris

Forest tree species provide many examples of well-studied adaptive differentiation, where the search for the underlying genes might be possible. In earlier studies and in our common conditions in a greenhouse, northern populations set bud earlier than southern ones. A difference in latitude of origin of one degree corresponded to a change of 1.4 days in number of days to terminal bud set of seedlings. Earlier physiological and ecological genetics work in conifers and other plants have suggested that such variation could be governed by phytochromes. Nucleotide variation was examined at two phytochrome loci (PHYP and PHYO, homologues of the Arabidopsis thaliana PHYB and PHYA, respectively) in three populations: northern Finland, southern Finland and northern Spain. In our samples of 12-15 sequences (2980 and 1156 base pairs at the two loci) we found very low nonsynonymous variation; pi was 0.0003 and 0.0002 at PHYP and PHYO loci, respectively. There was no functional differentiation between populations at the photosensory domains of either locus. The overall silent variation was also low, only 0.0024 for the PHYP locus. The low estimates of silent variation are consistent with the estimated low synonymous substitution rates between Pinus sylvestris and Picea abies at the PHYO locus. Despite the low level of nucleotide variation, haplotypic diversity was relatively high (0.42 and 0.41 for fragments of 1156 nucleotides) at the two loci.     

Inhibitory Effect of Brassinosteroids on the Flowering of the Short-Day Plant Pharbitis nil

The effect of exogenous brassinosteroids (BR) on the flowering induction of Pharbitis nil was examined. Generally plants treated with brassinolide and castasterone form less number of flowers than control plants, but degree of flowering inhibition was depended on the concentration and the method of BR application as well as the length of the inductive dark period. In plants regenerated from sub-induced apices treated with brassinolide at concentration of 1 and 10 M the flower formation was inhibited completely.     

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.     

Limits to adaptive plasticity: temperature and photoperiod influence shade-avoidance responses

In plants, the ratio of red to far-red wavelengths (R:FR) reliably indicates neighbor proximity and influences stem elongation. Enhanced elongation increases light interception and fitness under crowded conditions. However, many environmental factors vary simultaneously such that responses to R:FR may be affected by abiotic conditions or maternal environmental conditions. This study examines the effects of temperature, photoperiod, and maternal environment on stem-elongation responses to R:FR. Four populations of Abutilon theophrasti (two from disturbed, weedy areas and two from cornfields) were used in factorial common-garden experiments of temperature × R:FR × population and photoperiod × R:FR × population. Seedling growth of greenhouse- and field-derived seed was compared to evaluate maternal effects. Maternal environment did not alter seedling elongation. Higher temperatures resulted in both a twofold increase in average elongation and increased responsiveness to R:FR. Significant three-way interactions in both experiments demonstrate that population responses to R:FR differ depending on temperature and photoperiod conditions. These results indicate that elongation responses to R:FR are more variable than previously realized. The observed variability in elongation also suggests that the outcome of competitive interactions in the natural environment will depend on ambient temperature, photoperiod length, and population origin.     

Reversion of flowering in Glycine Max (Fabaceae)

Photoperiodic changes, if occurring before a commitment to flowering is established, can alter the morphological pattern of plant development. In this study, Glycine max (L.) Merrill cv. Ransom plants were initially grown under an inductive short-day (SD) photoperiod to promote flower evocation and then transferred to a long-day (LD) photoperiod to delay flower development by reestablishing vegetative growth (SD-LD plants). Some plants were transferred back to SD after 4-LD exposures to repromote flowering (SD-LD-SD plants). Alterations in organ initiation patterns, from floral to vegetative and back to floral, are characteristic of a reversion phenomenon. Morphological features that occurred at the shoot apical meristem in SD, LD, SD-LD, and SD-LD-SD plants were observed using scanning electron microscopy (SEM). Reverted plants initiated floral bracts and resumed initiation of trifoliolate leaves in the two-fifths floral phyllotaxy prior to terminal inflorescence development. When these plants matured, leaf-bract intermediates were positioned on the main stem instead of trifoliolate leaves. Plants transferred back to a SD photoperiod flowered earlier than those left in LD conditions. Results indicated that in plants transferred between SDs and LDs, photoperiod can influence organ initiation in florally evoked, but not committed, G. max plants.     

Diapause and survival in winter in two species of predatory bugs,Orius sauteri and O. minutus

The cause of differences in overwintering success between the sexes in Orius sauteri (Poppius) and O. minutus (Linnaeus) (Heteroptera: Anthocoridae) was investigated in the laboratory. The survival rate of adults was examined in a screen house outdoors during the winters of 1995–1996 and 1996–1997. None of the males of either species survived until spring in either year. However, 63.9% and 40.5% of the females in O. sauteri and O. minutus, respectively, survived the winter in 1995–1996, and 54.5% and 43.2%, respectively, in 1996–1997. Most of the males died by early winter. In both species, the adult females reared under short days (= L11:D13) survived for a long period at 5 or 0°C, while the males reared under the same photoperiod died shortly after transfer to 5 or 0°C from 22°C. The males and females kept at same temperature conditions under long days (= L16:D8) died early. When nymphs were kept under long days at 22°C, the lipid content in the female and male adults of O. sauteri was 27.9% and 17.7%, respectively. When nymphs were kept under short days, their lipid content was significantly higher (41.1%) than that of those reared under long days for females, but lipid content was comparable in the males regardless of photoperiod (15.6%). In O. minutus, the mean lipid content was 27.2% in females and 19.0% in males under long days at 22°C, and 40.8% in females and 19.8% in males under short days. Thus, a large amount of lipid was accumulated only in females kept under short days in both species. These results suggest that short days induced diapause only in adult females but not in males. Due to the lack of diapause and shortage of lipid accumulation, males may not be able to survive the winter.     

光质和光周期对山白兰苗木生长、生理的影响

为筛选出山白兰(Michelia baillonii)苗木培育过程中适宜的光环境，该研究以一年生山白兰幼苗为试验材料，设置12、16 h·d^-1两个光周期，配合使用红蓝复合光(8R1B、6R1B)、红蓝紫绿复合光(8R1B1P1G、6R1B1P1G)4种光质和白光(W)对照，采用双因素随机区组试验设计和隶属函数法，探讨了山白兰苗木生长、光合色素、内源激素含量对不同光质和光周期处理的响应规律。结果表明：(1)光质、光周期及其交互作用对山白兰苗高增长量、叶面积、叶绿素a、玉米素(ZR)、脱落酸(ABA)的含量、内源激素比值[IAA/ABA、(IAA+GA₃+ZR)/ABA]等均有显著影响(P<0.05)。(2)16 h·d^-1光周期有利于苗高增长量、叶面积、苗木质量指数、生物量、叶绿素a、生长素(IAA)、ZR的含量、内源激素比值的提高。(3)当光周期为16 h·d^-1时，8R1B处理下的苗高增长量、叶面积和苗木质量指数均最大，分别为21.84 cm、158.39 cm²和2...     

Effects of different photoperiods on the reproduction of the barbel, Barbus barbus (L.), reared at constant temperature

The role of photoperiod as an environmental factor controlling reproduction, particularly the duration and ending of the breeding season, in the barbel was investigated by tank experiments. The experiments used a population of barbel matured in captivity which were stripped of eggs at frequent intervals: 10–15 'spawnings'for each female were obtained at 15-day intervals.
A decreasing photoperiod (16·5 light: 7·5 dark→8L: 16D), for an annual cycle contracted to 6 months duration, inhibited the spawning of both female and male fish. This allowed two periods of reproduction (February-May and September-November) within one year. Under natural or constant (10L: 14D) photoperiod conditions, spawning came to an end spontaneously. The rate (accelerated, slow or natural) of daylength increase did not affect the onset of spawning.     

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.