Acceleration Of Flowering Research Articles

Molecular analysis of FRIGIDA, a major determinant of natural variation in Arabidopsis flowering time.

Vernalization, the acceleration of flowering by a long period of cold temperature, ensures that many plants overwinter vegetatively and flower in spring. In Arabidopsis, allelic variation at the FRIGIDA (FRI) locus is a major determinant of natural variation in flowering time. Dominant alleles of FRI confer late flowering, which is reversed to earliness by vernalization. We cloned FRI and analyzed the molecular basis of the allelic variation. Most of the early-flowering ecotypes analyzed carry FRI alleles containing one of two different deletions that disrupt the open reading frame. Loss-of-function mutations at FRI have thus provided the basis for the evolution of many early-flowering ecotypes.

Phytochrome D acts in the shade-avoidance syndrome in Arabidopsis by controlling elongation growth and flowering time.

Shade avoidance in higher plants is regulated by the action of multiple phytochrome (phy) species that detect changes in the red/far-red ratio (R/FR) of incident light and initiate a redirection of growth and an acceleration of flowering. The phyB mutant of Arabidopsis is constitutively elongated and early flowering and displays attenuated responses to both reduced R/FR and end-of-day far-red light, conditions that induce strong shade-avoidance reactions in wild-type plants. This indicates that phyB plays an important role in the control of shade avoidance. In Arabidopsis phyB and phyD are the products of a recently duplicated gene and share approximately 80% identity. We investigated the role played by phyD in shade avoidance by analyzing the responses of phyD-deficient mutants. Compared with the monogenic phyB mutant, the phyB-phyD double mutant flowers early and has a smaller leaf area, phenotypes that are characteristic of shade avoidance. Furthermore, compared with the monogenic phyB mutant, the phyB-phyD double mutant shows a more attenuated response to a reduced R/FR for these responses. Compared with the phyA-phyB double mutant, the phyA-phyB-phyD triple mutant has elongated petioles and displays an enhanced elongation of internodes in response to end-of-day far-red light. These characteristics indicate that phyD acts in the shade-avoidance syndrome by controlling flowering time and leaf area and that phyC and/or phyE also play a role.

Arabidopsis mutants showing an altered response to vernalization.

Flowering in many plant species is accelerated by a long period of cold temperature, known as a vernalization period. This research investigates how this cold temperature signal is perceived by plant cells and the mechanism by which it influences the transition to flowering. Mutagenesis of the late-flowering, vernalization-responsive, Arabidopsis mutant, fca, has yielded five independent mutations (termed vrn mutations) conferring an altered vernalization response. Allelism tests showed that these mutations fall into at least three complementation groups defining three loci named VRN 1, 2 and 3. The vrn1 and vrn2 mutations did not affect the acclimation response as judged by expression of cold-induced transcripts and freezing tolerance assays. vrn1-1 affected the short-day vernalization response of Landsberg erecta and reduced the vernalization response of other late-flowering Arabidopsis mutants. The acceleration of flowering by GA3 was not affected by vrn1-1. The VRN 1 locus was mapped to chromosome 3.

Retention of Phytochrome-Mediated Shade Avoidance Responses in Phytochrome-Deficient Mutants of Arabidopsis, Cucumber and Tomato

Summary Phytochrome-mediated shade avoidance responses have been studied in light-grown wild type and phytochrome-deficient mutant seedlings of Arabidopsis thaliana , tomato and cucumber. Light-grown seedlings of the long-hypocotyl hy -1, hy -2 and hy -6 mutants of A. thaliana retain a qualitatively normal shade avoidance response to growth under a low red: far-red (R:FR) ratio, namely an increase in elongation growth and a acceleration of flowering. This indicates that, despite the fact that etiolated tissues of these mutants are severely deficient in spectrophotometrically-detectable phytochrome, light-grown seedlings of the mutants possess some functional phytochrome. The hy -3 mutant, which is deficient in seed phytochrome, retains a similar, but less dramatic, shade avoidance response. The aurea ( au ) mutant of tomato, in which etiolated tissues are deficient in spectrophotometrically- and immunochemically-detectable phytochrome, also retains a qualitatively normal shade avoidance response to reduced R:FR ratio. This is consistent with the hypothesis that au seedlings are deficient only in a light-labile phytochrome species that normally accumulates in etiolated tissues and is involved in the deetiolation process. Light-grown seedlings of the long-hypocotyl ( lh ) mutant of cucumber, a mutation that appears to lead to a deficiency in a light-stable phytochrome species, retain a small, but significant, phytochrome-mediated increase in elongation growth in response to reduced R:FR ratio.

Observations of Effects of Partial Vernalization in Winter Rape Plants Grafted Onto Generative Stock

AbstractWinter rape plants vernalized under natural conditions were used as stock for grafting apical and subapical parts of rape seedlings vernalized at 5 °C in light during different periods ranging from 0 to 10 weeks. Acceleration of generative development in both kinds of grafts occurred already after 3 weeks of their vernalization, i.e. after cold treatment of insufficient length to induce flowering in plants developing independently. Effectiveness of vernalization — measured by acceleration of flowering in grafts was highest from 3rd to 5th week of cold treatment and then it declined. Processes occurring during an early stage of vernalization, though insufficient to allow independent generative development, become manifest in grafts made on vernalized stock. This allows investigations of very early stages of vernalization processes inaccessible to observation by other methods.

Control of Growth and Reproduction in Cultivated and Wild Rice by Light Quality and Dark Period

One cultivated and two wild rice varieties have been subjected to variation in photoperiod and light quality by daily exposure of the seedlings at the four-leaf stage to 8 h of natural daylight followed by white incandescent, red, green or blue light for 2,4 or 8 h in a temperature and humidity-controlled growth chamber. In some cases far-red irradiation was applied after white or red for 1 and 2 h. The treatments caused marked differences in growth and reproduction between the cultivated and wild rices. The cultivar Dudkalmi showed extensive tillering after far-red exposure. Earliest flowering was observed with a 16-h dark period both in the cultivated and wild rices. Failure of flowering with and 8-h day and 8-h artificial light of different wavelengths could be overcome by red or far-red of 1-h duration. The light quality interacted differently with the dark period in the acceleration of flowering in the three varieties. In another experiment the effects of interruption of the dark period by a light period of 2 h after from 4–12 h of darkness in a 24-h cycle were studied in the two wild rice varieties. Light of different wavelengths interposed in the dark period caused variation in tiller number and stem length in comparison to an uninterrupted dark period of 16 h. The effect at the beginning of the dark period was earlier flowering; flowering was delayed by interruption at 4 h and inhibited after 8 h but accelerated after a 10- to 12-h dark period. The results are discussed in the light of the significance of the dark period and light quality in regulating hormone balance and phytochrome reactions.

The Effects of Day Length and Light Intensity on Tile Growth of Barley

The acceleration of flowering in barley due to the inclusion of incandescent illumination in the light source has been shown to be due to the far�red content of the light. A linear relationship between floral development and intensity of far�red light in a 16�hr photoperiod has been established with the cultivar CI5611. Barley appears to be relatively unresponsive to blue light, however.

Acceleration of flowering of the long-day plant Arabidopsis by 8-azaadenine

The incorporation of 8-azaadenine (2×10(-5)M) to the aseptic culture medium reduced the time required for developing macroscopically visible flower primordia and the number of leaves appearing before the first flower buds to about half under 8 hrs daily illuumination in both wild type and a late monogenic mutant. In the presence of equimolar amount of adenine the flowering was not accelerated by the analog.

The effects of gamma-irradiation and storage temperature on the growth, flowering and bulb yield of wedgewood iris

Wedgewood iris bulbs were kept in common storage, at 25 °C, or subjected to 5 weeks of cold storage at 13 °, at the beginning or at the end of storage period. Bulbs were irradiated with cobalt-60, Y-irradiation (100–1500 r) at various stages of bud development. Irradiation of cooled bulbs accelerated flowering by up to 21 days. A radiation dose of 500 r accelerated flowering by 13 days without reducing flower stem length, when applied at a very early stage of bud growth (one week after beginning of cold storage). Irradiation at a later stage did not stimulate flowering. A few of the irradiated flowers were abnormal. All flowers were normal and no acceleration of flowering was noted in bulbs grown for the second year after irradiation. A slight stimulation of leaf and bulb growth was found with low irradiation doses applied to retarded bulbs (stored at 25 °C). Foliage length and bulb yield were progressively reduced by increasing doses of radiation. Irradiation was more detrimental to cooled bulbs than to common storage or 25 °C-stored bulbs.

Interactions of Gibberellin, Vernalization, Photoperiod and Temperature in the Flowering of Endive

Stem elongation and concomitant acceleration of flowering are well known responses of some higher plants to treatment with gibberellin (2, 3, 7, 8, 19, 20). It is clear that responsive biennials, such as henbane (Hyoscyamus niger L.) and carrot (Daucus carota L.) must reach a certain stage of development before either cold or gibberellin is effective in promoting seedstalk elongation and flowering (4, 5, 9, 19). Thus, in carrot a minimum root diameter of about 1 cm must be attained before flowering may be induced (4, 19). The flowering behavior of the biennials is in contrast to that of winter annual plants such as head lettuce (Lactuca sativa L.) and endive (Cichoritum endivia L.). The winter annuals, one of which is discussed in this paper, have only a quantitative requirement for cold. Flowering is hastened by a short period of seedling vernalization followed by a regimen of long days and high night temperatures (6, 10, 11, 12, 13, 14, 16, 18, 19). Application of gibberellin at any time after seed germination promotes stem growth and subsequent flowering of endive and of lettuce. The questions which the present experiments were designed to answer are: a) to what extent does gibberellin replace the cold and/or long day requirements for flowering of endive, and b) to what extent does gibberellin overcome temperatures unfavorable for seedstalk elongation.

Acceleration of Flowering in Non-vernalized Chrysanthemums by the Removal of Apical Sections of the Stem

Vince and Mason1 have reported recently that unvernalized plants of Chrysanthemum morifolium var. Sunbeam can be induced to produce flowering lateral shoots by decapitation of the main shoot. Under the stated conditions the main apex did not bud for a further four to six weeks. They suggest that inhibitory effects from the main apex are responsible for the failure of unvernalized plants to bud.

Acceleration of Flowering in Non-vernalized Chrysanthemums by the Removal of Apical Sections of the Stem

IT has been shown that plants of Chrysanthemum morifolium ‘Sunbeam’ (incorrectly termed ‘Indian Summer’), raised from basal cuttings taken from parent plants grown and flowered at high temperatures, require a period of low temperature or vernalization in order that normal stem elongation and rapid flowering may occur. Without such a period of low temperature these plants grown in high temperature conditions (> 60° F.) fail to elongate normally and are considerably delayed in flowering1.

Acceleration of flowering in partially vernalized grain of Petkus winter rye by subsequent treatment at high temperature.

Acceleration of Flowering in Partially Vernalized Grain of Petkus Winter Rye by Subsequent Treatment at High Temperature

Effects of High Temperature and Short Days on Vernalization Response of Summer Varieties of Rice

THE effect of high temperature on the acceleration of flowering in a number of varieties of rice has been reported previously1,2,3,4. In addition to early flowering, pre-sowing high-temperature treatment results in better resistance to drought conditions5. Vernalization by high temperature has practical difficulties. Radicles and plumules emerge from the seed coat during treatment, involving difficulty of transportation. This has been overcome in two varieties of rice noted below by limiting the moisture content of seeds to 30 per cent of fresh weight. Seeds at this moisture content germinated without the radicles and plumules penetrating the seed coat, and gave vernalization response when exposed to high temperature, 35° C., for 10 and 20 days (table).

Photoperiodic After-Effect

SEVERAL workers, notably Eghis, Rasumov and Dolgusin, claim to have demonstrated a photo-periodic after-effect with short-day plants, that is, an acceleration of flowering in such plants exposed to short days during the early stages of growth and afterwards grown in long days. This work has been done mainly on cereals and fodder plants, and so far as we are aware the existence of such an after-effect has not been demonstrated with any ornamental flowering plants.

EXPERIMENTS WITH FOLLICULAR AND OTHER HORMONES AND PLANT GROWTH

Summary.In the experiments described the writer failed to obtain accelerated growth or acceleration of flowering by presenting small quantities of ketohydroxyoestrin and theelol to flowering plants in different ways—in solution given to the roots, or by injection, or when applied to cut surfaces.From one experiment, designed for another purpose, possible confirmation of the results of Knight and Fildes was obtained in that auxin accelerated bacterial growth.