Short-day Treatment Research Articles

The Dynamics of Soybean Leaf and Shoot Apical Meristem Transcriptome Undergoing Floral Initiation Process

Flowering process governs seed set and thus affects agricultural productivity. Soybean, a major legume crop, requires short-day photoperiod conditions for flowering. While leaf-derived signal(s) are essential for the photoperiod-induced floral initiation process at the shoot apical meristem, molecular events associated with early floral transition stages in either leaves or shoot apical meristems are not well understood. To provide novel insights into the molecular basis of floral initiation, RNA-Seq was used to characterize the soybean transcriptome of leaf and micro-dissected shoot apical meristem at different time points after short-day treatment. Shoot apical meristem expressed a higher number of transcripts in comparison to that of leaf highlighting greater diversity and abundance of transcripts expressed in the shoot apical meristem. A total of 2951 shoot apical meristem and 13,609 leaf sequences with significant profile changes during the time course examined were identified. Most changes in mRNA level occurred after 1short-day treatment. Transcripts involved in mediating responses to stimulus including hormones or in various metabolic processes represent the top enriched GO functional category for the SAM and leaf dataset, respectively. Transcripts associated with protein degradation were also significantly changing in leaf and SAM implicating their involvement in triggering the developmental switch. RNA-Seq analysis of shoot apical meristem and leaf from soybean undergoing floral transition reveal major reprogramming events in leaves and the SAM that point toward hormones gibberellins (GA) and cytokinin as key regulators in the production of systemic flowering signal(s) in leaves. These hormones may form part of the systemic signals in addition to the established florigen, FLOWERING LOCUS T (FT). Further, evidence is emerging that the conversion of shoot apical meristem to inflorescence meristem is linked with the interplay of auxin, cytokinin and GA creating a low cytokinin and high GA environment.

Sex differences in Siberian hamster ultradian locomotor rhythms

Sex differences in ultradian activity rhythms (URs) and circadian rhythms (CRs) were assessed in Siberian hamsters kept in long day (LD) or short day (SD) photoperiods for 40weeks. For both sexes URs of locomotor activity were more prevalent, greater in amplitude and more robust in SDs. The UR period was longer in females than males in both day lengths. The reproductive system underwent regression and body mass declined during the initial 10weeks of SD treatment, and in both sexes these traits spontaneously reverted to the LD phenotype at or before 40weeks in SD, reflecting the development of neuroendocrine refractoriness to SD patterns of melatonin secretion. Hamsters of both sexes, however, continued to display SD-like URs at the 40weeks time point. CRs were less prevalent and the waveform less robust and lower in amplitude in SDs than LDs; the SD circadian waveform also did not revert to the long-day phenotype after 40weeks of SD treatment. Short day lengths enhanced ultradian and diminished circadian rhythms in both sexes. Day length controls several UR characteristics via gonadal steroid and melatonin-independent mechanisms. Sex differences in ultradian timing may contribute to sex diphenisms in rhythms of sleep, food intake and exercise.

Timing and duration of short-day treatment influence morphology and second bud flush in Picea abies seedlings

A slower reaction of diameter growth cessation compared to that of height growth in response to short day (SD) treatment is well documented in Picea abies (L.) Karst. seedlings, suggesting that the height/diameter ratio of seedlings could be controlled through appropriate timing and/ or duration of SD treatment is forest nurseries. Here, we applied specific combinations of timing (starting date 20 and 27 June, 4 or 11 July) and duration (7, 10, 14 or 17 days) of SD treatment to assess the possibility of obtaining more sturdy seedlings. We observed a rapid and uniform height growth cessation following SD treatment compared with the delayed cessation of diameter growth. Height growth responded significantly only to starting date of SD treatment, resulting in taller seedlings for later starting dates. Diameter growth responded to the duration of SD treatment, with significantly less diameter growth in seedlings exposed to 14 or 17 days of SD treatment than in seedlings exposed to 7 or 10 days of SD treatment. Also starting date influenced diameter growth, resulting in significantly more diameter growth with the earliest starting date compared with the two latest starting dates of the SD treatment. A second bud flush occurred only in seedlings exposed to SD treatment starting on 20 or 27 of June and only following 7–14 days of duration. This implies a need of longer duration if the SD treatment starts early. This will be at the expense of sustained diameter growth, thus compromising the objective of obtaining more sturdy seedlings.

Effects of photoperiod and temperature on diapause induction in Conogethes punctiferalis (Lepidoptera: Pyralidae)

The yellow peach moth, Conogethes punctiferalis (Guenée), a multivoltine species that overwinters as diapausing larvae, is one of the most serious insect pests on maize in China. Effect of photoperiod and temperature on larval diapause was examined under empirical laboratory conditions. Short-day treatments caused larval diapause at 25°C, and the critical photoperiod was between 12 and 13 h (or 12 h 51 min) light per day. No sensitive instar was identified for diapause induction under alternated short- (L : D 11 : 13 h) and long-day (L : D 14 : 10 h) treatments at different larval stages. However, accumulative treatment of three instars and 10 d under short-day treatment was required for the induction of 50% larval diapause. All larvae entered diapause at 20°C, whereas less than 3% did so at 30°C, irrespective of the long- or short-day treatment. Furthermore, under the short-day treatment, more than 90% of larvae went into diapause with temperatures ≤ 25°C, but less than 17% did so at 28°C. In contrast, under the long-day treatment, less than 19% of larvae went into diapause with temperatures ≥ 23°C. The forward shift (5°C) of critical temperature under the long-day regime demonstrated the compensatory effect of temperature and photoperiod on diapause induction. In conclusion, C. punctiferalis had a temperature-dependent type I photoperiodic diapause response; there was no sensitive instar for diapause determination, but the photoperiodic accumulation time countermeasures both of the short-day cycles and the number of instars exposed, and the photoperiodic diapause response, was a temperature-compensated phenomenon.

Winter Day Lengths Counteract Stimulatory Effects of Apomorphine and Yohimbine on Sexual Behavior of Male Syrian Hamsters

Yohimbine and apomorphine selectively act on noradrenergic and dopaminergic neural substrates to augment male sexual behavior (MSB) in several rodent species. The present study assessed whether these drugs can overcome the suppressive effects of short winter-like day lengths on MSB. Yohimbine treatments that markedly increase copulatory behavior of male hamsters in long days were completely ineffective in facilitating MSB when injected after gonadal regression induced by 16 wks of short day lengths and after complete gonadal recrudescence after 32 wks of short days; apomorphine was similarly ineffective. The brain circuit that mediates MSB either may be less responsive to yohimbine and apomorphine in short than long days, or these drugs may not produce equivalent neurotransmitter changes in the two day lengths. After 32 wks of short-day treatment, all males had undergone testicular recrudescence and successfully ejaculated on initial tests with sexually receptive females after a hiatus of at least 4 mo during which they were denied mating opportunities. This suggests that overwintering males in the field are in a state of reproductive readiness at the outset of spring conditions favorable for survival of offspring. (Author correspondence: piekarski@berkeley.edu)

Early season short-day treatment did not affect the field performance of Pinus sylvestris container seedlings in summer planting

When Scots pine (Pinus sylvestris L.) seedlings are short-day (SD) treated in May or early June, height growth ceases but seedlings reflush within a few weeks and grow secondary needles (later referred to as early SD treatment). These “2-year-old-like” seedlings have been thought to be more stress tolerant than traditional 1-year-old pine seedlings, and thus suitable for summer and autumn plantings. To test this, seedlings sown in April were early SD treated over a 3-week period from the beginning of June and the seedlings were planted at 10-day intervals from the beginning of July until the end of September, and also during the following spring. Neither survival nor height growth of early SD-treated seedlings differed from untreated (1-year-old) seedlings. Moreover, for both early SD-treated seedlings and 1-year-old seedlings, those planted in summer grew and survived better after planting but had more multiple leaders than seedlings planted in autumn or spring.

Effects of time and duration of short-day treatments under long-day conditions on flowering of a quantitative short-day sunflower (Helianthus annuus L.) ‘Sunrich Orange’

The effects of short-day (SD) treatment on differentiation, development and anthesis of flower buds, and on cut flower quality were investigated in a leading cut sunflower (Helianthus annuus L.) cultivar, Sunrich Orange, a quantitative SD plant. Plants were cultivated under long-day (LD) conditions with night interruption lighting from 2200 to 200h. SD treatment (11.5h photoperiod) for 1, 2, or 3 weeks was commenced at the cotyledon, two true leaves, or four true leaves stage. The control plants were grown under LD conditions throughout the experimental period. SD treatment for 1 or 2 weeks promoted flower bud initiation even when delivered at the cotyledon stage (9 days after sowing), indicating that the juvenile phase is very short in this cultivar. Flower differentiation and development were also accelerated by the SD treatment, and resulted in 19–39 days earlier anthesis. The quality of cut flowers was improved by SD treatment to desirable characteristics such as decreased weight, shortened stem and reduced stem diameter. The present study suggests that under LD conditions such as found in summer, SD treatment for 2 weeks from the cotyledon or two true leaves stage can promote LD-delayed flowering of quantitative SD sunflower plants without reducing cut flower quality.

Salicylic acid is involved in the regulation of starvation stress-induced flowering in Lemna paucicostata

The short-day plant, Lemna paucicostata (synonym Lemna aequinoctialis), was induced to flower when cultured in tap water without any additional nutrition under non-inductive long-day conditions. Flowering occurred in all three of the tested strains, and strain 6746 was the most sensitive to the starvation stress conditions. For each strain, the stress-induced flowering response was weaker than that induced by short-day treatment, and the stress-induced flowering of strain 6746 was completely inhibited by aminooxyacetic acid and l-2-aminooxy-3-phenylpropionic acid, which are inhibitors of phenylalanine ammonia-lyase. Significantly higher amounts of endogenous salicylic acid (SA) were detected in the fronds that flowered under the poor-nutrition conditions than in the vegetative fronds cultured under nutrition conditions, and exogenously applied SA promoted the flowering response. The results indicate that endogenous SA plays a role in the regulation of stress-induced flowering.

Development of Saccharina latissima (Phaeophyceae) kelp hatcheries with year-round production of zoospores and juvenile sporophytes on culture ropes for kelp aquaculture

Saccharina latissima is attractive for industrial cultivation for different usages, such as biofuels, feed supplements, and derivation of chemicals. A continuous supply of kelp sporelings throughout the year may ensure a year-round production of kelp juveniles on ropes. In this study, induction of sporangial areas (sorus portions) on the blade of S. latissima was performed throughout the year at three locations: Trondheim (Norway), Grenaa (Denmark), and Sylt island (Germany). The results indicate that a year-round sorus induction in S. latissima is possible and that this induction is controlled by applying short-day treatment of adult sporophytes throughout the year and by the removal of the basal blade meristem. The artificially induced and released zoospores formed viable sporelings at all seasons, but cultivation in the sea in Norway was successful only during autumn, winter, and spring, while the growth conditions were poor during the summer. The results are important for industrial scale-up and continuous production of kelp biomass.

Effects of Growth Duration on Grain Yield and Quality in Rice (Oryza sativa L.)

It is important to clear the relationships of growth duration with rice yield and quality in determining the breeding ob-jectives and cultivation strategies. In this paper, plants of japonica rice varieties Ning 111 and Chunjiang 302 with different growth durations resulted from short-day treatment were used to investigate the changes of yield and rice quality. The results showed that, the growth duration of more than 152 d had little effect on yield, but when less than 152 d, there was a significant positive correlation between growth duration and yield or dry matter accumulation; the smallest length and width of rice, as well as the lowest protein content and setback of amylum were observed in the treatments G2 or G3, which had moderate growth dura-tion of 131–132 d, the growth duration more than or less than 131–132 d would both increase the values of these rice quality indi-ces; amylose content also showed a similar trend, and the minimum value in two species all appeared in treatment G3 (132 d or 137 d), while for breakdown of amylum, the trend was just opposite. The percentage of chalky grains, chalkiness and gelatiniza-tion temperature in two varieties rose with shortening growth duration; the effects of growth duration on milling quality were gen-erally lower.

RELATIONSHIP BETWEEN PLANT ARCHITECTURE AND FRUIT PRODUCTION OF THE SHORT-DAY STRAWBERRY CULTIVAR 'GARIGUETTE'

This research was carried out to assess the relationship between the architecture of strawberry plants before chilling and winter-spring fruit production in a soilless forced culture system. On 11 September 2008, trayplants of the cultivar Gariguette were placed in a heated glasshouse and either exposed to long-day photoperiodic conditions or short-day photoperiodic conditions for 53 days. In addition, plants were held 26 days under short-day photoperiodic conditions followed by 27 days of long-day photoperiodic conditions or 26 days under long-day photoperiodic conditions followed by 27 days of short-day photoperiodic conditions. Architecture prior to chilling gave indications about the first fruit production period in winter-spring (1 March to 30 April 2009). The earliest short-day photoperiodic condition treatments produced the earliest fruits. These treatments exhibited the most developed inflorescences in the pre-chilling architectural analysis and the fewer nodes between the youngest expanded leaf and the terminal inflorescence. The plants that received 53 days of long-day photoperiodic conditions treatment had the least developed terminal inflorescence before chilling and the latest production. The architecture analysis of Gariguette trayplants could predict the earliness rank (first to last) but not the yield rank during the first harvest period.

Effects of Short-Day Treatment on Leaf Emergence Rate and its Turning Point in Several Cultivars of Rice

短日日長が水稲の生育，特に出葉転換点と出葉速度に与える影響を明らかにするために，ジャポニカ，インディカを含む8品種を自然日長および10時間日長条件で栽培した．移植日から止葉展開日までの出葉経過を2直線で近似し，その交点で表される出葉転換点と，各直線の傾きで表される出葉速度に対する日長と品種の影響を調査した．品種，処理，年次を要因とした3元配置分散分析の結果，交互作用は認められたものの，出葉転換点は短日処理により短縮されることが示された．また出葉転換点は早生品種で早く，晩生品種で遅いこと，止葉展開日との間に有意な正の相関関係が認められたことから，早晩性と関係していることが示唆された．出葉転換点と幼穂形成始期は同時期に認められることはなかったが，両者の間に有意な正の相関関係が認められた．出葉転換点以前 （L1）・以降 （L2） の出葉速度についても同様に3元配置分散分析を行ったところ， L1の出葉速度に対する短日処理の影響はコシヒカリやRayadaなどに限定されていたのに対し， L2ではTepi，Miritiを除く6品種において10時間日長区は自然日長区より有意に大きいことが明らかとなった．このことから，出葉転換点以降に出葉速度は短日処理の影響を受けやすくなることが示された．また品種間差異はL1，L2ともに認められ，特に早生で大きく，晩生で小さい傾向が認められた．一方で全生育期間を通して出葉速度が小さいMiritiのような品種も存在した．以上の結果から，出葉転換点はイネの体内生理的変化の指標となる可能性が示唆された．

Short Day–Mediated Cessation of Growth Requires the Downregulation of AINTEGUMENTALIKE1 Transcription Factor in Hybrid Aspen

Day length is a key environmental cue regulating the timing of major developmental transitions in plants. For example, in perennial plants such as the long-lived trees of the boreal forest, exposure to short days (SD) leads to the termination of meristem activity and bud set (referred to as growth cessation). The mechanism underlying SD–mediated induction of growth cessation is poorly understood. Here we show that the AIL1-AIL4 (AINTEGUMENTALIKE) transcription factors of the AP2 family are the downstream targets of the SD signal in the regulation of growth cessation response in hybrid aspen trees. AIL1 is expressed in the shoot apical meristem and leaf primordia, and exposure to SD signal downregulates AIL1 expression. Downregulation of AIL gene expression by SDs is altered in transgenic hybrid aspen plants that are defective in SD perception and/or response, e.g. PHYA or FT overexpressors. Importantly, SD–mediated regulation of growth cessation response is also affected by overexpression or downregulation of AIL gene expression. AIL1 protein can interact with the promoter of the key cell cycle genes, e.g. CYCD3.2, and downregulation of the expression of D-type cyclins after SD treatment is prevented by AIL1 overexpression. These data reveal that execution of SD–mediated growth cessation response requires the downregulation of AIL gene expression. Thus, while early acting components like PHYA and the CO/FT regulon are conserved in day-length regulation of flowering time and growth cessation between annual and perennial plants, signaling pathways downstream of SD perception diverge, with AIL transcription factors being novel targets of the CO/FT regulon connecting the perception of SD signal to the regulation of meristem activity.

Molecular dissection of an adaptive epigenetic memory mechanism in norway spruce

Molecular dissection of an adaptive epigenetic memory mechanism in norway spruce

Effect of Photoperiod on Key Enzyme Activities of Respiration in Nectarine Buds During Dormancy Induction

Shuguang ( Prunus persica var. nectariana cv. Shuguang) nectarine was used to study effects of photoperiod on key-enzyme activities of respiration during dormancy induction. The dormancy status was determined with sprouting ability. Spectrophotometry was used to investigate activities of phosphohexose isomerase (PGI), malic dehydrogenase (MDH), and glucose-6-phosphate dehydrogenase (G6PDH). The results revealed that short day (SD) treatment promoted dormancy induction while long day (LD) treatment postponed the process. During dormancy induction, PGI activities declined, MDH activities changed little, and G6PDH activities increased both in flower buds and leaf buds. PGI activities and MDH activities in SD treatment were lower than control, and G6PDH activities were higher, which was opposite with LD treatment. The changes of respiratory key-enzyme activities were adjusted by photoperiod and correlated with the development of dormancy induction.

Influence of short day treatment on autumn fruit production of June-bearing strawberry cultivars

Short-day (SD) strawberry cultivars were grown in 2008 and 2009 fall each year to evaluate effects of short-day (SD) treatment on flowering and fall fruit production in the high elevation of South Korea. In 2008, daughter plants of six cultivars ‘Maehyang’, ‘Seolhyang’, ‘Keumhyang’ (Korean short-day cultivars), ‘Akihime’, ‘Red pearl’, and ‘Sachinoka’ (Japanese short-day cultivars) were exposed to short-day (10-h photoperiods) conditions at the high elevation (HE, 800 m elevation) for 35 days beginning in late June. On 31 July, plants were removed from the SD environment and established in a substrate system at the highland. In 2009, the ‘Akihime’ and ‘Seolhyang’ were examined again. In 2008, flower bud initiation rate was above 90.0% for all cultivars except for ‘Akihime’ (83.3%). Fruit harvest commenced 1st of October 2008 and average fruit weight was consistently > 20g except for ‘Sachinoka’ (18 g). By mid-November, plants of ‘Seolhyang’ and ‘Akihime’ produced 222–260 more grams of fruit compared to other cultivars, with ‘Seolhyang’ having the earliest production. In 2009 experiment, flower bud initiation rates of ‘Akihime’ and ‘Seolhyang’ plants were 85.4% and 82.4%. Due to the earlier planting in 2009, fruit harvest commenced on 8 September (one month earlier than in 2008) and extended over 10 weeks. Yield and fruit numbers of ‘Akihime’ and ‘Seolhyang’ were 397.7 g, 22.7 and 331.7 g, 19.8, respectively. Results of this study indicate that exposure to SD photoperiods and relatively cool temperatures at HE can increase autumn fruit production in SD strawberry cultivars ‘Akihime’ and ‘Seolhyang’.

Expression of FLOWERING LOCUS T from Arabidopsis thaliana induces precocious flowering in soybean irrespective of maturity group and stem growth habit

The flowering integrator gene FLOWERING LOCUS T (FT) in Arabidopsis thaliana is conserved between diverse plant species and is thought to be the flowering signal ''florigen'', a universal long-distance mobile signal. In soybean, two FT homologs having a function to induce flowering in Arabidopsis have been identified. In this study, we showed that the expression of FT from Arabidopsis by the Apple latent spherical virus (ALSV) vector promoted precocious flowering and terminated vegetative growth in a wide range of genotypes of soybean, without using a short-day treatment. Four determinate and two indeterminate cultivars, infected with ALSV expressing FT (FT-ALSV), set flower buds on shoot apices and terminated vegetative growth at the fourth- to seventh-node stages under long-day conditions. In contrast, non-infected, healthy plants did not set flower buds on shoot apices at the same stage under the same conditions. After flowering, soybean cultivars infected with FT-ALSV, belonging to different maturity groups and stem growth habits, matured and produced seeds. The results suggest that the basic flowering pathway controlled by FT in A. thaliana might also be conserved in soybean. A system for precocious flowering and shortening of generation time using FT-ALSV would be a useful and novel technology for efficient soybean breeding.

Performance and quality of Cupressus sempervirens L. mini-plug seedlings under reduced photoperiod

Short-day treatment has been used for some conifer species to improve planting stock quality. The aim of this paper was to study the effect of short-day treatment on performance and quality of young seedlings of Italian cypress (Cupressus sempervirens L.), a conifer species abundant in the Mediterranean area. Seeds of Italian cypress were sown in mini-plug cavities. After 5 weeks of growth, seedlings were subjected to four different photoperiods: (a) 14 h (control), (b) 8 h, (c) 6 h, and (d) 4 h for a period of 1–3 weeks, before they were transplanted to bigger size containers. Reducing photoperiod did not result in bud formation or shoot inhibition although it increased the number of lateral shoots. Seedlings subjected to 6-h photoperiod for 2 weeks during pre-cultivation in mini-plugs had improved root characteristics, giving them a higher potential for outplanting success, especially in Mediterranean areas.

Bud break and spring frost hardiness in Picea abies seedlings in response to photoperiod and temperature treatments

Spring frost may result in detrimental damage in newly planted Picea abies (L.) Karst. seedlings if their growth rhythm is not sufficiently adapted to the climatic conditions on the forest site. The aims of this study were to evaluate how bud break and spring frost hardiness were influenced by short-day (SD) treatments with different timing and different temperature regimes during bud formation. Following winter storage, frost hardiness was tested after 1, 3 and 5 weeks in forcing conditions. The SD treatment advanced bud break compared with the control seedlings. In comparison, the effects of timing and the different temperatures on bud break were small. The SD treatment improved frost hardiness in first-year needles during dehardening. The early SD treatment resulted in improved frost hardiness in first-year needles and greater root collar diameter compared with later SD treatment. To avoid a second bud flush, it is important that a critical night length is attained when the SD treatment terminates. Low temperatures following the SD treatment resulted in increased hardiness of the needles and decreased hardiness of the stems. The contrasting effect of temperature in different plant tissues demonstrates the importance of examining different tissues following freezing tests.

Identification of genes associated with growth cessation and bud dormancy entrance using a dormancy-incapable tree mutant.

BackgroundIn many tree species the perception of short days (SD) can trigger growth cessation, dormancy entrance, and the establishment of a chilling requirement for bud break. The molecular mechanisms connecting photoperiod perception, growth cessation and dormancy entrance in perennials are not clearly understood. The peach [Prunus persica (L.) Batsch] evergrowing (evg) mutant fails to cease growth and therefore cannot enter dormancy under SD. We used the evg mutant to filter gene expression associated with growth cessation after exposure to SD. Wild-type and evg plants were grown under controlled conditions of long days (16 h/8 h) followed by transfer to SD (8 h/16 h) for eight weeks. Apical tissues were sampled at zero, one, two, four, and eight weeks of SD and suppression subtractive hybridization was performed between genotypes at the same time points.ResultsWe identified 23 up-regulated genes in the wild-type with respect to the mutant during SD exposure. We used quantitative real-time PCR to verify the expression of the differentially expressed genes in wild-type tissues following the transition to SD treatment. Three general expression patterns were evident: one group of genes decreased at the time of growth cessation (after 2 weeks in SD), another that increased immediately after the SD exposure and then remained steady, and another that increased throughout SD exposure.ConclusionsThe use of the dormancy-incapable mutant evg has allowed us to reduce the number of genes typically detected by differential display techniques for SD experiments. These genes are candidates for involvement in the signalling pathway leading from photoperiod perception to growth cessation and dormancy entrance and will be the target of future investigations.