• Journal of Korean Society of Forest Science
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• v.94 no.2 s.159
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• pp.67-72
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• 2005

The objectives of this study were to identify the period of initiation of floral primordia in black locust (Robinia pseudoacacia L.) and subsequent development of floral buds until following spring. Four mature trees of black locust located in Suwon, Korea were selected. Bud samples were collected from the current-year shoots, starting from mid June to July every week, from August to October and from February to April every month. The buds were fixed in FAA solution, dehydrated, and imbedded in paraffin for microscopic observation. Buds collected on June 16, and 23, 1997, contained primitive primordia that might be interpreted as early floral primordia. By June 30, a bud showed a positive indication of inflorescence primordium with a well-formed shoot apex. All the inflorescence primordia observed throughout the collection periods were always associated with unique hairy appendages around the primordium and enclosed within a sclerenchymatous chamber. By July 7 and 15, a floral apex had early bud scales. By July 22, primitive inflorescence developed into visible arrangement of individual floral primordial By July 29, the inflorescence developed into whirl arrangement of individual floral primordia in a transverse section, but showed little further development until October 15. The inflorescence primordia seemed to over-winter at this stage. Buds collected from February 15 and March 24 the following year also showed no further development of inflorescence primordia. By April 7 the inflorescence started to show further development with elongated axis. At this time individual flowers were easily recognized.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.2
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• pp.71-76
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• 1998

To define the relations between endogenous GA levels and growth and flowering in short-day plant sorghum, growth retardant BX-112 was applied to two sorghum genotypes, wild-type and phytochrome B mutant (phyB-1), which grows faster and flowers earlier than the wild-type. BX-112 and $GA_3$ were applied as a soil drench, and plant height, culm length, and date to floral initiation were investigated. Endogenous GAs contents were measured with GC-MS-SIM. BX-112 treatments inhibited shoot growth in both genotypes and drastically reduced $GA_1$ and $GA_8$ levels. With increasing BX-112 concentrations, $GA_1$ concentrations declined linearly, but caused the accumulation of intermediates from $GA_12$ to $GA_20$. This result implies that $GA_1$ is the major active endogenous GA in shoot elongation in a short day plant sorghum. The inhibition of plant growth in both of wild type and phyB-1 by BX-112 was very similar, while BX-112 effects on floral initiation in two types of plants differed significantly. Floral initiation of phyB-1 was not affected by BX-1l2, but that of wild-type was delayed as BX-1l2 concentration increased. Because BX-112 treatment causes accumulation of biosynthetic intermediates between synthetic pathway from $GA_12$ to $GA_20$ and because phyB-1 is altered in GA metabolism in this same region of the early C13-hydroxylation pathway, BX-112 may fail to block flowering of phyB-1.

• Korean Journal of Weed Science
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• v.17 no.2
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• pp.207-213
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• 1997

This study was conducted to correlate changes in plant growth and flowering behavior with inhibition of gibberellin synthesis following application of GA biosynthesis inhibitor. Two sorghum genotypes, wild-type and phyB-1(phytochrome B mutant) which grow fast and flowers early relative to the wild-type, were used. Both growth and floral initiation of these two genotypes were greatly affected by ancymidol concentration increased. However, these growth inhibition and delayed flowering are almost completely overcome by simultaneous applications of 31.6ppm $GA_3$. The ability of $GA_3$ to reverse the effect of the inhibition on both growth and floral initiation in sorghum suggests a role for native GAs in sorghum flowering. This result was contrast to the fact that in some long day plants GA biosynthesis inhibitors will inhibit shoot elongation but not floral initiation. In sorghum, inhibition of vegetative growth by GA biosynthesis inhibitor is accompanied by a delay in flowering. Ten ppm of ancymidol treatments drastically reduced all early-13-hydroxylation pathway GAs($GA_{12}$, $GA_{53}$, $GA_{19}$, $GA_{20}$, $GA_3$, and $GA_8$) levels.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.46 no.6
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• pp.478-482
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• 2001

This experiment conducted to know physiological characteristics and stress effect on different growth stage of soybean by night illumination. Soybean variety, Shinpaldalkong 2, Keumjungkong and Muhankong were treated by night illumination with 20~30 Lux (0.05~0.08W m$^{-2}$ , 0.24~0.36 $\mu$㏖ S$^{-1}$ m$^{-2}$ ) for 15 days at six different growth stage, seedling, pre-floral initiation, post-floral initiation, pod filling and seed ripening stage. Night illumination delayed flowering to 2~8 days compared to control. Delay of flowering by night illumination severely effected at the pre-floral initiation stage. Stem length was increased all the night illumination treatments except the pod filling stage. Number of nodes in Shinpaldalkong 2 and Keumjungkong 1 were increased until before post-floral initiation stage but in Muhankong were increased until after post-floral initiation stage by night illumination treatments. Number of pods were decreased all the night illumination treatments except seedling stage compared with control. Yield decreased all the treatments and severe the loss rate degree showed the order of prefloral initiation, post-floral initiation, seedling and flowering stage.

• 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.

• Horticultural Science & Technology
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• v.19 no.4
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• pp.560-563
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• 2001

To determine the minimum number of short day (SD) required for flower initiation and development of chrysanthemum, plants were exposed to SD and long day (LD) conditions. Floral development was significantly different between continuous exposure of 16 hour long day (LD) condition and 2 or 4 SD prior to LD in chrysan-themum cvs. Envy and Lady Time, respectively. As more SD exposure was given, final leaf number was decreased and floral stage was advanced, suggesting a facultative response to photoperiodic cycles. Therefore, only 2-4 days of SD were enough to induce flower initiation. After 6 weeks of SD condition, the plants continued anthesis regardless of subsequent photoperiods. The long day leaf number (LDLN) varied between cultivars as 38.0 and 45.4 in Envy and Lady Time, respectively.

• Horticultural Science & Technology
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• v.31 no.6
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• pp.726-731
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• 2013

Experiments were conducted to evaluate the effect of low temperature-darkness treatment on floral initiation in four kinds of Korean strawberry cultivars. Mother plants were planted on March 29 and daughter plants were raised for the experiment. Temperature treatment was done for 7, 14, and 21 days keeping $13^{\circ}C$ in cooling storage from August 29, September 5 and September 14 to September 21. After the treatment, flower bud initiation was examined by a microscope, and the seedlings were transplanted on hydroponic system with Yamazaki's strawberry solution of EC $0.8dS{\cdot}m^{-1}$ to check the flowering. 'Ssanta' and 'Maehyang' showed early flower bud initiation in 7 days treatment than 'Seolhyang' by microscope check. 'Ssanta', 'Daewang', and 'Maehyang' showed early flower bud initiation in 14 days treatment than 'Seolhyang'. There were no differences among the treatments in 21 days treatment. Percentage of flowering of 'Seolhyang' and 'Maehyang' by low temperature-darkness treatment didn't show any difference but 'Daewang' and 'Ssanta' showed high percentage of flowering. It suggested that low temperature-darkness treatment technique can be use for improving early flowering and yield of 'Ssanta' and 'Daewang' cultivars.

• Horticultural Science & Technology
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• v.29 no.2
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• pp.135-143
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• 2011

In the Doritaenopsis hybrid, like most of the orchid species and hybrids, temperature is crucial for the vegetative-to-reproductive transition, and low temperature is required for bud differentiation. To understand the molecular mechanism of this process, an orchid GIGANTEA (GI) gene, DhGI1, was isolated and characterized by using the rapid amplification of cDNA ends (RACE) PCR technique. Sequence analysis showed that the full-length cDNA is 4,022 bp with a major open reading frame of 3,483 bp, and the amino acid sequence showed high similarity to GI proteins in Zea mays, Oryza sativa, Arabidopsis thaliana and other plants. Semi-quantitative RT-PCR revealed that DhGI1 was expressed throughout development and could be detected in roots, stems, leaves, peduncles and flower buds. The expression level of DhGI1 was higher when the plants were flowering at low temperature (22/$18^{\circ}C$ day/night) than the other growth stages. Further analysis indicated that the accumulation of DhGI1 transcripts was significantly increased at low temperature, and concomitantly, initiation of the peduncle was observed. However, DhGI1 levels were low under high temperature (30/$25^{\circ}C$) conditions, and flower initiation was inhibited. These results indicate that the expression of DhGI1 is regulated by low temperature and that DhGI1 may play an important role in inflorescence initiation in this Doritaenopsis hybrid at low temperatures.

• Korean Journal of Plant Resources
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• v.31 no.6
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• pp.591-596
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• 2018

This study was conducted to develop gibberellin treatment technique to enhance flower initiation in Aquilegia japonica Nakai & H. Hara. Seedlings were planted in 12cm-diameter pots on October 2016 and grown in green house. Ambient temperature in the green house was set at minimum $15^{\circ}C$ during day and night to suppress flower initiation at cold temperature condition. Two different types of gibberellin, $GA_3$ and $GA_{4+7}$, at 4 different concentration levels 100, 200, 400 and 600 mg/L, were tested in this study. Gibberellin was sprayed first at planting and secondly at 1-week after planting. Ten to fifteen ml of gibberellin was sprayed for each pot. Plant height and petiole length were elongated by both gibberellin types, flowering was more enhanced by $GA_3$ (91.7~100%) compared to of $GA_{4+7}$. However, abnormal flower was less observed in $GA_3$ treatment (0~16.7%) than $GA_{4+7}$. Number of flower stalks per plant ranged from 1.9 to 2.5. Number of flowers per plant ranged from 6.8 to 10.3. Differences in flowering characteristics between treatments were statistically significant. Optimal gibberellin treatment to enhance flower initiation in A. japonica Nakai & H. Hara substituting cold treatment was $GA_3$ at the concentration between 400 mg/L to 600 mg/L.

• Journal of Korean Society of Forest Science
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• v.59 no.1
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• pp.31-36
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• 1983

Flowering time of Pinus rigida Mill and Pinus taeda L, in an $F_1$-hybrid seed orchard was investigated for five years from 1971 through 1975. The two tree species flowered during late April to early May at the observation site, Flowering patterns of the two species of different sex of the same species changed yearly during the five observation years. Floral development of the two species appeared to depend largely on temperature factor during the period of the initiation of floral organs up to flowering provided that other environmental factors are normal. Six-days difference in flowing time between female inflorescence of pitch (flower later) and male inflorescence of loblolly (flower earlier) pines effectively isolated the two species reproductively on population levels. Not all of selected trees of the two species for their synchronized flowering appeared to be useful as parental trees for the establishment of $F_1$-hybrid seed orchards. With the result from this investigation the author suggested to use a modified simple recurrent selection method for pitch-loblolly hybrid pine breeding.