• Horticultural Science & Technology
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• v.34 no.1
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• pp.55-66
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• 2016

This study was carried out to investigate the effect of artificial light sources with different light qualities on the growth and flowering characteristics of a herbaceous long-day plant, Petunia ${\times}$ hybrida Hort. Seedlings of petunia cultivar 'Madness Rose' were potted, acclimated for one week, and grown in a phytotron equipped with tube- and bulb-type fluorescent lamps (FL tube and bulb), tube-type white light-emitting diodes (LED tube), halogen lamps (HL), metal halide lamps (MH), and high pressure sodium lamps (HPS) for 10 weeks. The temperature, photoperiod, and photosynthetic photon flux density (PPFD) in the phytotron were $22{\pm}2^{\circ}C$, 16 h, and $25{\pm}2{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$, respectively. Light sources combined with HL promoted stem elongation, and plant height and internode length decreased with increasing red to far-red (R:FR) ratio. FL tube + LED tube, HPS, and FL tube promoted branching, whereas plants grown under light sources combined with HL did not have any branches. Days to flowering (from longest to shortest) occurred as follows: FL tube + HL > FL tube + HL > MH > HPS = FL tube + FL bulb > FL tube + LED tube > LED tube > FL tube, indicating that reducing the R:FR ratio of the light sources promoted flowering. Only 20% of plants grown under an FL tube flowered, whereas under all other treatments, 100% of plants flowered. At 10 weeks after treatment, plants grown under HPS and MH had (cumulatively) 12 open flowers, and those grown under FL tube + FL bulb, LED tube, FL tube + LED tube, and HPS treatment had approximately seven flower buds. These results suggest that light sources with low R:FR ratios promote flowering and stem elongation in petunia, but they reduce its ornamental value due to overgrowth and poor branching.

• FLOWER RESEARCH JOURNAL
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• v.16 no.4
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• pp.247-254
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• 2008

This study was conducted to investigate effect of temperature, photoperiod, and plant growth regulators on the growth and flowering of Dendrobium phalaenopsis. Photoperiod treatments of 10 or 16 day length were from Mar. 24 to May 23. After treatments, all plants were exposed under natural photoperiod. Temperature treatments promoted development of new shoots (leads) of Dendrobium phalaenopsis 'Semi Alba' at $30/25^{\circ}C$(day/night) for 12 weeks, and 16 hr-photoperiod treatment promoted development of new shoots and flowering. The 16 hr photoperiod Dendrobium phalaenopsis 'Candistraipe ${\times}$ Tedtakiguz' no difference in the numbers of flower, flower width, and stalk length compared to the 10 hr photoperiod. Days to first flowering from appearance of new shoot were 241 days under natural photoperiod, 243 days under 10 hr, and 216 days under 16 hr, so that 16 hr-photoperiod treatment was faster about 25 days than that of natural or 10 hr treatment. There was not significant difference in growing and flowering of Dendrobium phalaenopsis among plant growth regulators.

• FLOWER RESEARCH JOURNAL
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• v.17 no.4
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• pp.266-270
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• 2009

This experiment was conducted to investigate the effect of transfer date to a growth chamber and low temperature on growth and flowering of Jeffersonia dubia for free control of flowering period. According to transfer date, any plant did not sprout when plants were put in a growth chamber from Aug. 20 to Dec. 20. However, all the plants which were put in a growth chamber on Jan. 20 or Feb. 20 sprouted and resulted in flowering. The effect of beginning time and period of low temperature treatment were also observed. At the beginning time of Aug. 20, sprouting and flowering occurred as plant received more than 60 days of low temperature treatment. However, almost of al l the plants sprouted and flowered by only 30 days of low temperature treatment when the low temperature was given after Sep. 20. 60 days of low temperature given again after about three month growing period after dormancy breaking, resulted in resprouting of all plants and 70% of them flowered in this experiment.

• FLOWER RESEARCH JOURNAL
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• v.26 no.4
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• pp.179-186
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• 2018

Ranunculus asiaticus characterizes colorful and attractive flower shapes that are related with the ornamental value of bulbous plants. Improving ornamental value of bulbous flowers has been the general goal of floricultural market. Gibberellic acid ($GA_3$) and benzyladenine (BA) play an important role in growth and developmental processes in floriculture. Combinational treatments of these two hormones have been used in floriculture to improve flower quality. We assessed the effects of combined $GA_3$ and BA, as well as the individual effects of each hormone, on growth characteristics using soil drench application to eight R. asiaticus cultivars, 'Giallo Millepetali', 'Bianco Millepetali', 'Arancio Millepetali', 'Rosa SC', 'Arancio Pratolino', 'Giallo Pratolino', 'Bianco Pratolino', and 'Rosa Ch Pratolino'. $GA_3$ treatments increased plant height and first flower size of R. asiaticus cultivars. Moreover, about 5 to 9 days to flowering were averagely shortened by $GA_3$ treatments compared to controls. On the other hand, the opposites, including first flower size and days to flowering, were observed for cultivars treated with BA, compared with controls. Treatments of $GA_3$ + BA generally affected growth traits, such as plant height, flower size, and the timing of flowering on some R. asiaticus cultivars. In particular, about 5 to 6 days to flowering were reduced on average by Treatments of $GA_3$ + BA. Our results showed positive growth effects, including plant height, days to flowering, first flower height, number of flowers from the application of individual and combined hormones to R. asiaticus cultivars and demonstrate a role for these hormones in future bulbous floriculture.

• Korean Journal of Remote Sensing
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• v.38 no.1
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• pp.57-72
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• 2022

In this paper, we aimed to examine the flowering dates of cherry blossom and the peak dates of maple leaves in South Korea, by the combination of temperature observation data from ASOS (Automated Surface Observing System) and NDVI (Normalized Difference Vegetation Index) from MODIS (Moderate Resolution Imaging Spectroradiometer). The more recent years, the faster the flowering dates and the slower the peak dates. This is because of the impacts of climate change with the increase of air temperature in South Korea. By reflecting the climate change, our statistical models could reasonably predict the plant phenology with the CC (Correlation Coefficient) of 0.870 and the MAE (Mean Absolute Error) of 3.3 days for the flowering dates of cherry blossom, and the CC of 0.805 and the MAE of 3.8 for the peak dates of maple leaves. We could suppose a linear relationship between the plant phenology DOY (day of year) and the environmental factors like temperature and NDVI, which should be inspected in more detail. We found that the flowering date of cherry blossom was closely related to the monthly mean temperature of February and March, and the peak date of maple leaves was much associated with the accumulated temperature. Amore sophisticated future work will be required to examine the plant phenology using higher-resolution satellite images and additional meteorological variables like the diurnal temperature range sensitive to plant phenology. Using meteorological grid can help produce the spatially continuous raster maps for plant phenology.

• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.4
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• pp.396-402
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• 2014

The spring season in Korea features a dynamic landscape with a variety of flowers such as magnolias, azaleas, forsythias, cherry blossoms and royal azaleas flowering sequentially one after another. However, the narrowing of south-north differences in flowering dates and those among the flower species was observed in 2014, taking a toll on economic and shared communal values of seasonal landscape. This study was carried out to determine whether the 2014 incidence is an outlier or a mega trend in spring phenology. Data on flowering dates of forsythias and cherry blossoms, two typical spring flower species, as observed for the recent 60 years in 6 weather stations of Korea Meteorological Administration (KMA) indicate that the difference spanning the flowering date of forsythias, the flower blooming earlier in spring, and that of cherry blossoms that flower later than forsythias was 30 days at the longest and 14 days on an average in the climatological normal year for the period 1951-1980, comparing with the period 1981-2010 when the difference narrowed to 21 days at the longest and 11 days on an average. The year 2014 in particular saw the gap further narrowing down to 7 days, making it possible to see forsythias and cherry blossoms blooming at the same time in the same location. 'Cherry blossom front' took 20 days in traveling from Busan, the earliest flowering station, to Incheon, the latest flowering station, in the case of the 1951-1980 normal year, while 16 days for the 1981-2010 and 6 days for 2014 were observed. The delay in flowering date of forsythias for each time period was 20, 17, and 12 days, respectively. It is presumed that the recent climate change pattern in the Korean Peninsula as indicated by rapid temperature hikes in late spring contrastive to slow temperature rise in early spring immediately after dormancy release brought forward the flowering date of cherry blossoms which comes later than forsythias which flowers early in spring. Thermal time based heating requirements for flowering of 2 species were estimated by analyzing the 60 year data at the 6 locations and used to predict flowering date in 2014. The root mean square error for the prediction was within 2 days from the observed flowering dates in both species at all 6 locations, showing a feasibility of thermal time as a prognostic tool.

• Korean Journal of Plant Resources
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• v.21 no.1
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• pp.1-4
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• 2008

The clonal variation in female flowering was studied in Larix leptolepis clone bank, consisting of 116 clones, for three years. The between-year variation was large; i.e. the percentage of flowering grafts and average number of flowering per graft were $28.4{\sim}67.2$ and $9{\sim}176$, respectively. Differences in flowering abundance among clones were large and statistically significant in all the years studied. The variance of flowering abundance among clones was increased when flowering was poor. The average of broad-sense heritability of flowering abundance was 0.52. The genetic gain(%G) was estimated at 57.4% when the upper 30% clones were selected. The clonal stability of flowering abundance was compared using average number of flowering and coefficient of variance value of each clone. The clones such as Gyeonggi 9(29), Kangwon 37(137), Chungnam 6(46), Chungnam 14(414), R11, R8 showed abundant flowering and high stability.

• Horticultural Science & Technology
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• v.34 no.2
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• pp.207-219
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• 2016

Incandescent (INC) lamps have been commonly used to promote flowering of long-day (LD) plants during short-day (SD) seasons, but production of INC lamps has been prohibited due to their low energy efficiency. One of the light sources replacing INC lamps is a compact fluorescent lamp (CFL). This study was carried out to compare the flowering and morphological responses of LD annuals grown in a controlled environment greenhouse at $20^{\circ}C$ with a truncated 9-h SD and a 2- or 4-h night interruption (NI) or 6-h day extension (DE) provided by lighting from INC lamps, CFLs, or a combination of the two (INC + CFLs), in which red (R) to far-red (FR) ratios were 0.60, 8.46, and 0.91, respectively, and their PPFDs were $2.3{\pm}0.3{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$. After 12 weeks of treatment, $Petunia{\times}hybrida$ 'Wave Purple' plants did not flower under the SD photoperiod whereas 100% flowered under all of the LD treatments. Flowering was more rapid under the INC or INC + CFL lighting treatments compared to CFL and DE, and 4-h NI enhanced flowering compared to 2-h NI. In addition, plants under DE and 4h-NI generally flowered earlier than under 2-h NI. All petunia 'Single Dreams Red' plants flowered within 65 days after treatment, and flowering was hastened by some LD lighting regimens and lamp types. Plants under DE and 4h-NI generally flowered earlier than under 2-h NI INC or INC + CFL compared to FL, and flowering time under INC 6-h DE was earliest. In addition, INC lighting promoted stem elongation of both petunia cultivars. In both pansy (Viola${\times}wittrockiana$) 'Coiossus Yellow' and 'Delta Blue Blotch', LD treatments, especially using INC lamps, promoted flowering whereas the lighting period had little influence on days to flowering. Therefore, INC or INC + CFL with lower R:FR promoted flowering and stem extension and the promoting effect was larger with longer lighting periods. These results suggest that CFLs can be used to provide LDs to promote the flowering of petunia and pansy and to reduce stem elongation, although the promoting effect on flowering is sometimes less than that of INC lamps alone.

• Journal of Plant Biotechnology
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• v.44 no.4
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• pp.438-447
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• 2017

Flowering is one of the most important development traits related to the production of Brassica rapa crops. After planting, a sudden low temperature triggers premature flowering, which leads to a reduction in the yield and quality of harvested production. Therefore, understanding the mechanism of flowering control is important in the agricultural productivity for preventing Brassica rapa crops. Vernalization is generally known as the main factor of flowering in the Brassica plant. However, in the subspecies of Brassica rapa, some accession such as Yellow sarson and Komatsuna display the flowering phenotype without vernalization. Circadian genes, which diurnally regulate plant physiology, have a role for photoperiodic flowering but are related to the regulation of the vernalizarion mechanism. In this report, the 22 B. rapa accession were divided into two groups, vernalization and non-vernalization, and the sequenced circadian gene, BrPRR1s. Among them, the BrPRR1b gene was found to have deletion regions, which could classify the two groups. The PCR primer was designed to amplify a short band of 422bp in the vernalization type and a long band of 451bp in the non-vernalization type. This primer set was applied to distinguish the flowering types in the 43 B. rapa accession and 4 Brassica genus crop, Broccoli, cabbage, mustard, and rape. The PCR analysis results and flowering time information of each crop demonstrated that the primer set can be used as marker to discern the flowering type in Brassica crops. This marker system can be applied to the B. rapa breeding when selecting the flowering character of new progenies or introducing varieties at an early stage. In addition, these results displayed that the circadian clock genes can be a good strategy for the flowering control of B. rapa crops.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.62 no.4
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• pp.304-310
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• 2017

This study was conducted over a 3-year period from 2013 to 2015 in the mid-northern inland, Cheolweon, Korea, to investigate changes in flowering date, daily mean temperature during grain filling, and yield characteristics affected by transplanting date in an early-maturing rice variety, 'Joun'. Thirty-day-old seedlings were transplanted at four different dates at 15-day interval from May 5 to June 19. Flowering dates were July 16, July 21, July 31, and August 14 when transplanting was performed on May 5, May 20, June 4, and June 19, respectively. Late transplanting resulted in higher daily mean temperature before flowering but late-transplanted rice required fewer days and lower cumulative temperature to reach flowering from transplanting. As transplanting was delayed, daily mean temperature for 40 days after flowering decreased, whereas daily sunshine hours for the same period increased, with a temperature of $24.8^{\circ}C$ and sunshine for 5.8 hours being recorded at the transplanting on May 5, and with a temperature of $21.0^{\circ}C$ and sunshine for 7.7 hours at the transplanting on June 19. With late transplanting, panicles per square meter significantly decreased, whereas spikelets per panicle showed an increasing trend. Regression analysis showed that maximum head rice yield was attained from the transplanting on May 18, for which the flowering date was July 21, and daily mean temperature for 40 days from that flowering date was $24.6^{\circ}C$. A decrease in head rice yield by 5% and 10% of the maximum was observed for rice transplanted on June 6 and June 15, which resulted in flowering dates of August 2 and August 11, respectively, and the daily mean temperatures for 40 days from flowering were 23.2 and $21.7^{\circ}C$, respectively. Therefore, in mid-northern inland, it is recommended to transplant 'Joun' on May 18 to induce flowering on July 21, when grain filling is subjected to a daily mean temperature of $24.6^{\circ}C$ during active filling stage.