Flowering Of Short-day Plants Research Articles

Photons from NIR LEDs can delay flowering in short-day soybean and Cannabis: Implications for phytochrome activity.

Photons during the dark period delay flowering in short-day plants (SDP). Red photons applied at night convert phytochromes to the active far-red absorbing form (Pfr), leading to inhibition of flowering. Far-red photons (greater than 700 nm) re-induce flowering when applied after a pulse of red photons during the dark period. However, far-red photons at sufficiently high intensity and duration delay flowering in sensitive species. Mechanistically, this response occurs because phytochrome-red (Pr) absorbance is not zero beyond 700 nm. We applied nighttime photons from near infrared (NIR) LEDs (peak 850 nm) over a 12 h dark period. Flowering was delayed in Glycine max and Cannabis sativa (two photosensitive species) by 3 and 12 days, respectively, as the flux of photons from NIR LEDs was increased up to 83 and 116 μmol m-2 s-1. This suggests that long wavelength photons from NIR LEDs can activate phytochromes (convert Pr to Pfr) and thus alter plant development.

Identification of the specific long-noncoding RNAs involved in night-break mediated flowering retardation in Chenopodium quinoa

BackgroundNight-break (NB) has been proven to repress flowering of short-day plants (SDPs). Long-noncoding RNAs (lncRNAs) play key roles in plant flowering. However, investigation of the relationship between lncRNAs and NB responses is still limited, especially in Chenopodium quinoa, an important short-day coarse cereal.ResultsIn this study, we performed strand-specific RNA-seq of leaf samples collected from quinoa seedlings treated by SD and NB. A total of 4914 high-confidence lncRNAs were identified, out of which 91 lncRNAs showed specific responses to SD and NB. Based on the expression profiles, we identified 17 positive- and 7 negative-flowering lncRNAs. Co-expression network analysis indicated that 1653 mRNAs were the common targets of both types of flowering lncRNAs. By mapping these targets to the known flowering pathways in model plants, we found some pivotal flowering homologs, including 2 florigen encoding genes (FT (FLOWERING LOCUS T) and TSF (TWIN SISTER of FT) homologs), 3 circadian clock related genes (EARLY FLOWERING 3 (ELF3), LATE ELONGATED HYPOCOTYL (LHY) and ELONGATED HYPOCOTYL 5 (HY5) homologs), 2 photoreceptor genes (PHYTOCHROME A (PHYA) and CRYPTOCHROME1 (CRY1) homologs), 1 B-BOX type CONSTANS (CO) homolog and 1 RELATED TO ABI3/VP1 (RAV1) homolog, were specifically affected by NB and competed by the positive and negative-flowering lncRNAs. We speculated that these potential flowering lncRNAs may mediate quinoa NB responses by modifying the expression of the floral homologous genes.ConclusionsTogether, the findings in this study will deepen our understanding of the roles of lncRNAs in NB responses, and provide valuable information for functional characterization in future.

How Supplementary or Night-Interrupting Low-Intensity Blue Light Affects the Flower Induction in Chrysanthemum, A Qualitative Short-Day Plant.

This research examined the effects of the supplementary or night-interrupting (NI) blue (B) light supplied at a low intensity on the flowering, gene expression, and morphogenesis of chrysanthemum, a qualitative short-day plant. White (W) light-emitting diodes (LEDs) were used to provide light with a photosynthetic photon flux density (PPFD) of 180 μmol·m−2·s−1 during the photoperiod to grow the plants in a plant factory. The control group was constructed with plants that were exposed to a 10-h short day (SD10) treatment without any blue light. The B light in this research was used for 4 h to either (1) extend the photoperiod for plants at the end of a 9-h short day (SD) treatment as the sole light source (SD9 + 4B), (2) provide night interruption (NI) to plants in the 13-h long-day (LD) treatment (LD13 + NI − 4B), (3) provide NI to plants in the 10-h SD treatment (SD10 + NI − 4B), or (4) supplement the W LEDs at the end of a 13-h LD treatment (LD13 + 4B). Blue LEDs were used to provide the supplementary/NI light at 10 μmol·m−2·s−1 PPFD. The LD13 + NI − 4B treatment resulted in the greatest plant height, followed by LD13 + 4B. Plants in all treatments flowered. It is noteworthy that despite the fact that chrysanthemum is a qualitative SD plant, chrysanthemum plants flowered when grown in the LD13 + 4B and LD13 + NI − 4B treatments. Plants grown in the LD13 + 4B had the greatest number of flowers. Plants grown in the LD13 + 4B treatment had the highest expression levels of the cryptochrome 1, phytochrome A, and phytochrome B genes. The results of this study indicate that a 4-h supplementation of B light during the photoperiod increases flower bud formation and promotes flowering, and presents a possibility as an alternative method to using blackout curtains in LD seasons to practically induce flowering. The B light application methods to induce flowering in SD plants requires further research.

The effect of exogenous acetylcholine and other cholinergic agents on photoperiodic flower induction of Pharbitis nil

Exogenous acetylcholine (ACh), acetylcholinesterase (AChE) inhibitors, as well as agonists and antagonists of ACh receptors applied on the cotyledons of 5-day-old seedlings of <em>Pharbitis nil</em> during a 16-hour long inductive night or during a 12-hour long subinductive night, do not essentially influence the flower bud formation. Also the application of above mentioned substances to the seedlings growing under the conditions of 72 hours of darkness, 24 hours of light and then 24 hours of darkness does not influence in an essential way flowering of <em>P. nil</em>. On the other hand, applying these substances on the cotyledons of <em>P. nil</em> during 24-hour-long inductive night, preceded by 72 hours of darkness and then 24 hours of light of lowered intensity finished by 15-minute-long impulse of far red light which inhibit flowering, caused the reversion of the effect of far red light irradiation and stimulated the flowering. The obtained results suggest that endogenous system ACh/AChE could participate in the mechanism of a phytochrome controlled flowering of short day plants.

Ethylene and ABA interactions in the regulation of flower induction in Pharbitis nil

Hormones are included in the essential elements that control the induction of flowering. Ethylene is thought to be a strong inhibitor of flowering in short day plants (SDPs), whereas the involvement of abscisic acid (ABA) in the regulation of flowering of plants is not well understood. The dual role of ABA in the photoperiodic flower induction of the SDP Pharbitis nil and the interaction between ABA and ethylene were examined in the present experiments. Application of ABA on the cotyledons during the inductive 16-h-long night inhibited flowering. However, ABA application on the cotyledons or the shoot apices during the subinductive 12-h-long night resulted in slight stimulation of flowering. Application of ABA also resulted in enhanced ethylene production. Whereas nordihydroguaiaretic acid (NDGA) - an ABA biosynthesis inhibitor - applied on the cotyledons of 5-d-old seedlings during the inductive night inhibited both the formation of axillary and of terminal flower buds, application of 2-aminoethoxyvinylglycine (AVG) and 2,5-norbornadiene (NBD) - inhibitors of ethylene action - reversed the inhibitory effect of ABA on flowering. ABA levels in the cotyledons of seedlings exposed to a 16-h-long inductive night markedly increased. Such an effect was not observed when the inductive night was interrupted with a 15-min-long red light pulse or when seedlings were treated at the same time with gaseous ethylene during the dark period. Lower levels of ABA were observed in seedlings treated with NDGA during the inductive night. These results may suggest that ABA plays an important role in the photoperiodic induction of flowering in P. nil seedlings, and that the inhibitory effect of ethylene on P. nil flowering inhibition may depend on its influence on the ABA level. A reversal of the inhibitory effect of ethylene on flower induction through a simultaneous treatment of induced seedlings with both ethylene and ABA strongly supports this hypothesis.

Suppression of the Floral ActivatorHd3aIs the Principal Cause of the Night Break Effect in Rice[W

A short exposure to light in the middle of the night causes inhibition of flowering in short-day plants. This phenomenon is called night break (NB) and has been used extensively as a tool to study the photoperiodic control of flowering for many years. However, at the molecular level, very little is known about this phenomenon. In rice (Oryza sativa), 10 min of light exposure in the middle of a 14-h night caused a clear delay in flowering. A single NB strongly suppressed the mRNA of Hd3a, a homolog of Arabidopsis thaliana FLOWERING LOCUS T (FT), whereas the mRNAs of OsGI and Hd1 were not affected. The NB effect on Hd3a mRNA was maximal in the middle of the 14-h night. The phyB mutation abolished the NB effect on flowering and Hd3a mRNA, indicating that the NB effect was mediated by phytochrome B. Because expression of the other FT-like genes was very low and not appreciably affected by NB, our results strongly suggest that the suppression of Hd3a mRNA is the principal cause of the NB effect on flowering in rice.

An experimental study on the growth and flowering of riparian pioneer plants under long- and short-day conditions

Plants of 19 annual taxa from the hygro-nitrophilous vegetation of Central European river banks and dried ponds were exposed as seedlings for 42 days to either natural long days (LD=ca. 15.5 h) or artificial short days (SD=11 h). Phenological and morphological growth parameters such as first flowering, main stem length, leaf size and plant dry weight were measured and compared. Based on their day-length responses, the plants were classified as 11 short-day plants (SDP), 6 long-day plants (LDP) and 2±day neutral plants (DNP). Differences of morphological plant responses under SD (compared with those under LD) reached from none to almost negligible ones in Ranunculus sceleratus, Bidens cernua, Chenopodium ficifolium and Rumex palustris to an extreme reduction in all parameters, as in Chenopodium glaucum× rubrum, Ch. rubrum, Ch. glaucum, Ch. polyspermum, Bidens radiata, Persicaria lapathifolia subsp. brittingeri and subsp. lapathifolia. Growth inhibition was usually combined with neotenic flowering in SDP. Some LDP exhibited clear dormancy responses, like the formation of smaller (winter) rosettes. Erosulate therophytes were mostly SDP while (hemi)rosulate to caespitose winter annuals or short-lived hemicryptophytes were LDP. Plants of seven species that were exposed to natural SD in spring (increasing day length) showed rather different responses. While Bidens radiata flowered in late spring soon after floral induction, other species showed increasing degrees of flowering delay ( Chenopodium polyspermum→ Xanthium saccharatum→ Chenopodium rubrum). Only Atriplex prostrata did not exhibit any sign of floral induction until (decreasing) SD in late summer arrived. In the case of Chenopodium rubrum details of the divergent morphogenesis under SD and LD were studied. In this species SD lead to strong reduction of stem length, leaf number and leaf size, simplification of leaf outline and margins as well as an enhanced ramification in the axils of primary leaves (and cotyledons) instead of metaphylls. The study reveals that for the phytosociological vegetation group Chenopodion rubri, whose populations are mainly confined to river banks with moist but well-aerated sediments, erosulate, therophytic and often neotenic SDP are typical. For the species of the Bidention – that thrive preferentially at the margins of stagnant water on rather wet soils – (hemi)rosulate or caespitose winter annuals are frequent. They are often LDP and survive the cold season in a vegetative state, even under a shallow level of water. The SD response of therophytic pioneers together with an often strong neotenic plasticity is interpreted here as a reassurance for the plants to flower and set seed in riparian habitats that are available for colonization only for a short and insecure period of the year, which due to the asymmetric position of annual low water levels in larger rivers is often not before mid-summer.

A-1 Researches for flowering by control of light and by treatment of plant hormons.(Part 1 Effects of blue-light, green-light and red-light on flowering of short-day plants and long-day plants.)

A-1 Researches for flowering by control of light and by treatment of plant hormons.(Part 1 Effects of blue-light, green-light and red-light on flowering of short-day plants and long-day plants.)

Control of Flowering of Xanthium pensylvanicum by Red and Far-red Light

A study was made of the effects of various durations, intensities and combinations of red and far-red light interruptions on the flowering responses of Xanthium pensylvanicum Wallr. A dual response to treatments of far-red light was observed. In short dark periods, far-red light alone did not greatly affect flowering but was able to overcome the inhibition of flowering caused by red light. In dark periods longer than 15 hours, far-red inhibited flowering and added to rather than overcame the inhibition by red light. The dark period length required for far-red inhibition remained the same whether far-red was given at the start or at the eighth hour of darkness.In 48-hour dark periods Xanthium showed 3 responses to additions of red and far-red light breaks: A) response to red light; B) response to far-red light; and C) response to red followed by far-red light. Red light given any time in the first 30 hours of darkness overcame the inhibitory effect of far-red light given at either the start or the eighth hour of darkness. Red light given later than the thirtieth hour did not overcome the far-red effect.Approximately the same energy of red light was required to overcome the inhibitory effect of far-red at the second hour of darkness as was required to produce maximum red light inhibition at the eighth hour. Although far-red light was most inhibitory when given early in a long dark period, approximately the same energy of far-red light was required to saturate the far-red response at the fourth, eighth and sixteenth hours.The results are discussed in relation to other reports of far-red inhibition of flowering in short-day plants.

Some physiological responses to d,l abscisin (dormin)

The responses to synthetic d,l abscisin have been studied in a variety of tests. When fed in aqueous solution continuously to leaves of seedlings growing under long day conditions, d,l abscisin caused the cessation of extension growth and the formation of typical resting-buds in Betula pubescens, Acer pseudoplatanus and Ribes nigrum. Abscisin also inhibited the growth of non-dormant buds of potato when applied to the whole tubers, but was much less effective when applied to isolated tuber plugs.Abscisin accelerates the senescence of leaf discs of a wide variety of species, but is less effective when sprayed on to attached leaves, except at relatively high concentrations (50-100 ppm).Abscisin inhibited flower induction in the long day species, Lolium temulentum and Spinacia oleracea, when applied to the leaves during a period of exposure to 15-long-day cycles. Abscisin promoted flowering in the short-day plants Pharbitis nil, Ribes nigrum and strawberry when applied under long day conditions, but it did not induce flowering in certain other typical short day plants. Tuberization in Solanum andigena and two cultivars of S. tuberosum was promoted by abscisin when applied to the leaves of plants growing under long-day conditions.

Significance of Dark Reversion of Phytochrome in Flowering of Short-Day Plants

Significance of Dark Reversion of Phytochrome in Flowering of Short-Day Plants

カゼクサ種子の発芽における光週期的処理

1. Light is obligatory for the germination of Eragrostis seeds but the dark period corresponding to that in flowering of short-day plants is required immediately after soaking. And the high-intensity-light process prior to the dark process is not observed. Germination is maximal under the dark period of 24hrs. followed by light and decreases under continuous light irradiation.2. The germination-promoting effects of the long dark period are inhibited by brief interruptions with red, blue or far-red energy, such interruptions being most effective for red and blue at the 9th hr. after the start of the dark period, and for far-red energy in the latter half of the dark period.3. Repeated alternations of red and far-red radiant energies repeatedly result in red inhibition and far-red repromotion of germination in the first half of the dark period, but not in the latter half.4. Another important feature is the photocontrol of germination by a succession of alternate blue and far-red irradiations in the first half of the dark period. The germination is regulated by the light last received, being inhibited with blue energy and repromoted with far-red.

Studies on the blindness in gladiolus. V

Many studies on the physiology of flowering clari-fied that the flowering in short-day plants may be controlled by the application of plant growth regulating substances, the so-called “auxin” or “antiauxin”. It is recognized in the gladiolus culture that the .short day promotes the flowering slightly, but ex-treme short day causes the blindness. It is supposed that the application of growth regulating substance is effective to decrease the number of blindness in gladiolus, For the first step of the study from the point of view mentioned above, the experiments were conducted to know the auxin level in the flower buds of gladiolus which had been held under long photoperiods (24 hours) and short photoperiods (8 hours). The variety used was “Spotlight”. The average-weight of corms which had been grown at Ueno in Mie prefecture was 26. 5g. The corms were plant-ed in the experimental farm of Kyoto University on August 27, 1958. Shading and lighting were made from October 10 to November 6, 1958. Sampl-ings were made at one-week intervals during the .course of the experiments and the avena tests were mad eon each sample. Avena sativa, variety Victory grown at Hokkaido University was used for the .curvature test. And the diffusion method, in which 3 hours diffusion was made at 25°C, was employed for the test. Beside avena test, anatomical obser-vations were made. The results obtained were summarized as follows: 1. Two weeks after the start of treatment, it -was observed that the length of flower spikes in short-day plot was getting shorter than that in long-day plot, nevertheless no difference was observ-ed between long-day and short-day plots on height of plants, number of leaves, and length of stems. And the difference in length of spike increased gradually as the time progressed. Finally, the blindness occurred in short-day plot, four weeks after the start of treatment. 2. The value of avena test with the plants under short-day condition was smaller than that under long-day condition two weeks after the start of treatment. And as the time progressed, the difference in the measurement values between long-day and short-day plots became greater. Finally, few avenas were curved with the plants under short-day. 3. Anatomical observations showed that the death of cells appeared at the top of the flower spike in three week treatments of short-day. Then the death of cells advanced downwards with the succeed-ing of treatment. The perfect death of flower spike was observed in the samples taken from the plants treated with four week short photoperiods. The archesporium formation was observed in the flower buds that died at their most developed stage. 4. From the results mentioned above, it seems that the gladiolus under short-day condition results in the decrease in auxin content in the flower buds, and consequently shows the blindness. 5. Anatomical studies showed that the flower buds, which had reached to the tetrard stage at the end of four week short-day treatments, were not damaged.

Influence of Light and Darkness upon Carbon Dioxide Fixation.

For plants sensitive to photoperiodism light is generally essential for flowering, and the requirement for C02 with the light indicates a photosynthetic function for the light period (21, 10). There appears to be an additional role of light in which it apparently alters a photoreceptor pigment controlling floral initiation (22). Evidence has been advanced recently that C02 is also essential during the dark period for floral initiation in some short day plants (13) as also in the allied phenomenon of vernalization of Alaska peas (15). Gregory et al (8) and Langston and Leopold (13) have suggested that the C02 metabolism in darkness is closely related to the photoperiodic response of short day plants. It would be interesting to know more concerning the products of C02 fixation in this connection. Calvin and co-workers (4) have demonstrated that products of dark and light fixation of C02 by green plants are dependent upon preceding light and dark conditions. It has long been accepted that some materials synthesized in a high intensity light process are utilized in the long dark period essential for flowering of short day plants (9). This suggests that a study of C*02 fixation in light and darkness during the period of photoperiodic induction with the aid of Chromatographie and autoradiographic techniques may yield useful information regarding the biochemistry of the photoperiodic reactions.

A New Photoperiodic Phenomenon in Short-Day Plants

THE classical researches of Hamner1 on photo-periodism indicated that the flowering of short-day plants, such as Biloxi soybean, is dependent upon exposure to a certain minimum (‘critical’) dark period. Within certain limits, the length of the critical dark period is largely independent of the duration of the light period, but when the latter reaches 20 hr., flowering in Biloxi soybean will not occur even if the associated dark periods exceed the critical value. The possibility that the length of this limiting light period may vary with the duration of the dark period has apparently never been investigated.

THE EFFECT OF VARIOUS WAVEBANDS OF SUPPLEMENTARY RADIATION ON THE PHOTOPERIODIC RESPONSE OF CERTAIN PLANTS

The effect of various wavebands of visible radiation, used to lengthen short daylight periods, on the photoperiodic response of plants has been the subject of considerable disagreement. Schappelle (9) concludes that supplemental red and blue radiation are equally effective in inducing flowering in radish and spinach, that red is more effective than blue in the case of China aster and early flowering cosmos and that blue is more effective than red in the case of lettuce, although red induces flowering. Salvia, chrysanthemum, Kalanchoe, teosinte, and Maryland Broadleaf tobacco failed to flower under any radiation prolonging the daylength to more than ten hours. Funke (3, 4, 5) divided his results into four types of flowering response when he supplemented an 8-hour day with red, blue, and white radiations. Group I included those plants which flowered under short days and blue at the same time and under white and red at the same time ; plants of group II failed to flower under short days but flowered under all long day conditions ; those in group III flowered only under white radiation and under no other condition ; and those in group IV flowered simultaneously under white and blue radiation and under red and dark at the same time. He used a light intensity of from 30 to 60 lux (approximately 3 to 6 foot candles) and a temperature of 12? to 15? C. Rasumov (8) found that, in general, red light acted like white light in inducing flowering in long day plants and inhibiting flowering in short day plants ; green, blue, and violet light acted like darkness. He found, however, a variable sensitivity to differences in wavelengths of radiation. Withrow and Benedict (11), and Withrow and Blebel (12) found that red and white radiation induced early flowering in long day plants and inhibited flowering in short day plants. Short day plants flowered in days lengthened with green and blue light, as well as under short days. Some long day plants, such as China aster and Helianthus cucumerifolius also flowered under blue radiation at the same time as under the red, while Scabiosa, another long day plant, failed to flower under the blue. The plants were grown at 50? F. night and 55? F. day temperature.