• Journal of Plant Biology
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• v.38 no.3
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• pp.227-234
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• 1995

Exogenous putrescine of 0.5 mM or higher concentratons applied during a 16 h inductive dark period could elevate putrescine content in cotyledons of Pharbitis nil Choisy cv. Violet, a short-day plant, resulting in complete blocking of photoperiodic floral induction. Titers of putrescine, spermidine and spermine in the cotyledons were traced throughout a 16 h dark period. While non-induced cotyledons under continous light slightly increased levels of polyamines, induced tissue maintaiend its putrescine, spermidine and spermine levels as low as 66.4%, 60.9% and 84.9% of non-induced levels respecitvely. Endogenous polyamines kept at lower levels in the inductive dark period were found to upsurge by a night break treatment of 10 min light in the middle of the dark and consequently the inductive dark effect was canceled. Elevation of polyamine titers could also be induced by 100 $\mu$L/L ethylene treatment which completely suppressed floral induction. Compared to untreated cotyledons, ehtylene-treated tissues increased putrescine content by as much as 136.5% in 12 h and spermidine level by up to 130.1% in 8 h. Ethylene-treated cotyledons not only increased endogenous polyamine content but also liberate ethylene in the second half of the inductive dark period accumulating up to three to fourfold level supporting a hypothesis that ethylene-treated tissues are stimulated to produce ethylene which in turn accelerates polyamine biosynthesis in the tissues. It is postulated that substantially low polyamine titers in the inductive dark period would be one of the necessary factors controlling photoperiodic induction of flowering in Pharbitis nil and the inhibitory effects of night break and exogenous ethylene treatment may be atributed to their action to stimulate endogenous polyamine production.

• Horticultural Science & Technology
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• v.33 no.1
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• pp.31-38
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• 2015

This study was carried out to investigate the relationship between endogenous polyamines (PAs) and floral bud differentiation in chrysanthemum (Chrysanthemum morifolium). In this study, PA content (free, bound, and conjugated) in apical buds, leaves, and roots changed appreciably during floral bud differentiation. PAs accumulated during series of processes such as floral induction, differentiation of floret primordia, and crown formation in apical buds; changes in PAs in apical buds may have a relationship with those in leaves and roots. The levels of free PAs and conjugated PAs [putrescine (Put) and spermine (Spm)] in apical buds rapidly increased during the initiation stage of floral bud differentiation, while free and conjugated spermidine (Spd) reached their highest levels at the stage of floret primordium differentiation. In the free, conjugated, and bound PA fractions, the changes in Spm content were negligible compared to those of Put and Spd throughout the experiment. These findings indicate that PAs participate in regulating the process of flower bud differentiation in chrysanthemum.

• Journal of Plant Biology
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• v.19 no.1
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• pp.14-18
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• 1976

Inhibition of flowering in Lemna perpusilla 6746 by 30 mM sucrose was reversed by the addition of acetylcholine (>$10^{-4}M) supplemented with 10^{-4}M$ ascorbic acid to 1/10-strength Hunter's growth medium. The reversible effect of acetylcholine was found to be greater at early stages of flowering than in the later period. Promotive effects of both acetylcholine ($10^{-3}M) and eserine(10^{-5}M$) on flowering in the short-day plant under various photoperiodic conditions were studied. It was indicated that the application decreased length of the critical dark period for the floral induction, and it was also shown that the endogenous status of acetylcholine was involved in the floral response which had a correlation with phytochrome. Interruption of inductive dark periods by red irradiation (1min) immediately followed by far-red light (1 min) completely inhibited flowering, while the addition of acetylcholine and eserine to the medium under the same condition slightly promoted flowering, indicating possible involvement of phytochrome system in acetylcholine activity for photoperiodic sensitivity of floral response in Lemna perpusilla 6746.

• Journal of Plant Biology
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• v.39 no.4
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• pp.257-263
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• 1996

Flower-inducing activity in the phloem exudata of Pharbitis cotyledons was investigated using the bioassay of Pharbitis and Lemna. By SDS-PAGE and 2-D gel electrophoresis of the phloem exudate, two polypeptides of 11 kDa and of approximately 32 kDa (pI 6.9) showing qualitative changes during the flower induction were detected. A polypeptide of approximately 20 kDa (pI 4.8) specifically labeled in vivo with [35S]methionine was found during the inductive dark period in Pharbitis cotyledon tissues. The polypeptide of the equivalent molecular mass and with the identicl pI value was also detected by in vitro translation assay. Thus, it is assumed that the 20 kDa polypeptide plays a role in the process of flower induction in Pharbitis cotyledons.

• Journal of Photoscience
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• v.5 no.3
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• pp.131-135
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• 1998

Using differential display reverse transcription technique, the present study attempted to isolate and characterize genes specifically expressed in cotyledons of Pharbitis nil Choisy cv. Violet during floral induction. A total of 107 bands specific to the inductive condition were initially obtained with 80 primer sets of 20 different arbitrary primers combined with 4 kinds of T12MN. In northern blot analysis with reamplified cDNAs as probes, three cDNAs were detected to be expressed specificcally in the induced cotyledon tissues, and designated PnFL-1, PnFL-2 and PnFL-3 , the size of which were 228 bp, 317 bp and 272 bp, respectively. A search for sequences similar to the decuced amino acid sequences was conducted using GenBank and EMBL database ; seequence encoded by PnFL-1 had 29% identity with the clone of Arabidopsis thaliana similiar to reverse trascriptase (Genbank Acc. N0.3047086), PnFL-2 shared 50% identity with hydroxiyproline-rich glycoprotein of Glycine max(GenBank Acc. No.347455), and PnFL-3 had 46% identity with TAMU 4. Thaliana genomic clone T23E16 (GenBank Acc. No.B67574). None of them was known gene in the plant system up to date, implying that the fragments may comprise parts of genes which are associated with the floral induction in Pharbitis nil.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.1
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• pp.1-8
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• 1995

This study was carried out to investigate the effects of floral inhibition of An-gelica gigas NAKAI in the hilly altitude located in the Northern Gyeongbuk Province from Feb. 1992 to Nov. 1994. The results obtained were as follows ： As the cultivated areas are high, rate of bolting was significantly decreased, having high yield, good growth, and medicinal quality. It is considered that the optimal cultivating area was at least above 600m altitude. In the hilly altitude, the more shorten nursery period was, the more decreased rate of bolting was, it results in decreased yield, having no significant differences in contents such as extracts and decursin. In bolting response from temperature treatment of the seedlings, treatment of high temperature was significantly decreased floral induction, but rate of establishment was decreased by decayed root. Bolting rate at different organic resources has more reduced in single fertilization than that of in organic application, but among organic resources, compost of rice straw has the lowest bolting rate. As a result, yield and medicinal qualities at various organic resources were increased in application of organic resources which was no con-siderable tendency among organic resources.

• Genes and Genomics
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• v.40 no.12
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• pp.1259-1267
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• 2018

Litchi (Litchi chinensis Sonn.) is an important subtropical fruit crop with high commercial value due to its high nutritional values and favorable tastes. However, irregular bearing attributed to unstable flowering is a major ongoing problem for litchi producers. Previous studies indicate that low-temperature is a key factor in litchi floral induction. In order to reveal the genetic and molecular mechanisms underlying the reproductive process in litchi, we had analyzed the transcriptome of buds before and after low-temperature induction using RNA-seq technology. A key flower bud differentiation associated gene, a homologue of FLORICAULA/LEAFY, was identified and named LcLFY (GenBank Accession No. KF008435). The cDNA sequence of LcLFY encodes a putative protein of 388 amino acids. To gain insight into the role of LcLFY, the temporal expression level of this gene was measured by real-time RT-PCR. LcLFY was highly expressed in flower buds and its expression correlated with the floral developmental stage. Heterologous expression of LcLFY in transgenic tobacco plants induced precocious flowering. Meantime, we investigated the sub-cellular localization of LcLFY. The LcLFY-Green fluorescent protein (GFP) fusion protein was found in the nucleus. The results suggest that LcLFY plays a pivotal role as a transcription factor in controlling the transition to flowering and in the development of floral organs in litchi.

• Journal of Plant Biology
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• v.20 no.2
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• pp.77-82
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• 1977

The inhibiotory effect of ethphon on the flowering in Lemna perpusilla 6746 was shown to be related to sucrose concentrations and dilution factors of Hutner's medium. When grown in 1/10-strength Hutner's medium under 10(14) cycles, the plants have been completely inhibited in the floral induction by ethephon (>5ppm) in the presence of sucrose (>20 mM) in the meduim. However, in a less diluted Hutner's medium (1/2-strength), the inhibition of flowering by ethephon was observed to be partially diminished by sucrose at a high concentration (30mM), while a low concentration of sucrose enhanced the inhibitory effect of ethephon in flowering. As inductive dark periodswere extended, the effects of both compounds were partially nullified. Since no significant amount of ethylene possibly released in ethephon decomposition in the medium was detected, the inhibitory effect of ethephon in flowering was postulated to be exerted only through ethylene production within the plants. Plants were incubated in 10 ppm ethephon-containing medium during either dark or light periods, singly or periodically. The most effective single treatment with ethephon was observed during the 4th dark period, when formation of floral stimulus was assumed to be completed beyond a critical level. This postulation can be partially supported by a fact that the plants should be exposed to at least more than four consecutive 10(14) cycles for flowering.

• Proceedings of the Botanical Society of Korea Conference
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• 2000.04a
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• pp.30-30
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• 2000

• Proceedings of the Botanical Society of Korea Conference
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• 1987.07a
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• pp.213-237
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• 1987

In vitro flowering system may minimize the confounded influence of non-floral meristem parts of plants in studying the relationship of a given treatment and flowering responses. We have induced flower buds from plantlets regenerated from zygotic embryo-derived somatic embryos of ginseng, which circumvented the normal 2-year juvenile period before flowering. The result suggests that the adulthood of ginseng root explants in the experiment previously conducted by Chang and Hsing (1980; Nature 284: 341-342) is not prerequired to flowering of plantlets regenerated through somatic embryogenesis. We have also induced flower buds from elongated axillary brandches from cotyledonary nodes by culturing ginseng zygotic embryos, seedlings, and excised cotyledonary nodes. It was found that 6-benzyladenine (BA) supplemented to the medium was essential for flowering, whereas abscisic acid (ABA) was inhibitory. Gibberellic acid(GA3) was also required for flowering when ABA was present with BA in the medium. The results suggest that cytokinins, gibberellins, and inhibitors play primary, permissive, and preventive roles, respective-ly, in the induction of flowering of ginseng. Tran Thanh Van (1980; Int. Rev. Cytol., Suppl. IIA: 175-194) has developed the "thin cell layer system" in which the induction of shoots, roots, or flower buds from epidermal layer explants were controlled by culture conditions and exogenous growth regulators in the medium, Utilizing the thin cell layer system, Meeks-Wagner et al. (1989; The Plant Cell 1: 25-35) have cloned genes specifically expressed during floral evocation. However, the system is too tedious for obtaining a sufficient amount of plant materials for biochmical and molecular biological studies of flowering. We have developed a garlic callus culture system and one obvious advantaging over the thin cell layer system is that an abundant cells committed to develope into flower buds proliferate. When the above cells were compared by two-dimensional gel electrophoresis with those which have just lost the competence for developing into flower buds, a few putative proteins specific to floral evocation were detected. The garlic callus culture system can be further explored for elucidation of the molecular biological mechanism of floral evocation and morphogenesis.hogenesis.