HORTSCIENCE 54(8):1370–1374. 2019. https://doi.org/10.21273/HORTSCI14156-19 Kunming is the main production area of paniculata in China, with 28 years of cultivation history (Yang, 2012). Effects of Seasonal Variation and Due to its location (altitude, 1900 m; latitude, 25 N), Kunming has the mildest climate in Gibberellic Acid Treatment on the China (Liang et al., 2017). The perpetual spring-like weather provides ideal growth Growth and Development of conditions for , but it is still difficult for Gypsophila paniculata to bloom during Gypsophila paniculata winter because of the low temperatures at night. Usually, the seedlings of Gypsophila Fan Li, Guoxian Wang, Rongpei Yu, Min Wu, Qinli Shan, Lifang Wu, paniculata are planted from March until the Jiwei Ruan1, and Chunmei Yang1 end of August in Kunming; then, they are harvested twice during the forthcoming year. National Engineering Research Center for Ornamental Horticulture, Key If the seedlings are planted after September, Laboratory for Flower Breeding of Yunnan Province, Floriculture Research then the rosette plants will appear. These Institute, Yunnan Academy of Agricultural Sciences, Kunming 650200, China rosette plants are more significant during winter. Few studies have focused on applying Additional index words. flowering regulation, growth regulator, rosette, season, sensitive gibberellins to induce floral stems and pro- Abstract. We investigated the effects of different planting seasons and gibberellic acid voke blooming in Gypsophila panicu- treatments on the growth and development of Gypsophila paniculata to explore new lata. Therefore, we examined the seasonal approaches to controlling the flowering period. Four different were selected and variations in the growth and development of continually planted in July, September, and November in the low-latitude and high- four different cultivars of Gypsophila pan- altitude region of Kunming, China (258 N, 1028 E). Results showed that the vegetative iculata. Our results showed that Gypsoph- growth and flowering time of Gypsophila paniculata were prolonged and postponed when ila paniculata is season-sensitive, and that the planting time was delayed. Specifically, ‘My Pink’ showed 20% and 80% rosette rates some cultivars cannot flower during autumn when grown in autumn and winter, respectively, thus indicating that Gypsophila and winter. To overcome this, we applied growth regulator GA3 to control the growth paniculata is sensitive to planting time. Moreover, GA3 treatment not only can significantly promote vegetative growth but also can stimulate early flowering and and flowering of different cultivars. The suppress the occurrence of rosettes during winter. This is more specific to ‘My Pink’, study showed that two different GA3 treat- ments have positive effects on the vegetative which showed 40% and 80% reductions in rosette rates with four and eight GA3 treatment applications, respectively. Our study showed that seasonal variations in the growth and flowering regulation of Gypsoph- ila paniculata during winter, thus providing a growth and development of Gypsophila paniculata and GA3 treatment can effectively stimulate early flowering and suppress rosettes during winter. simple method of enhancing flower produc- tion.

Gypsophila paniculata, a flowering plant plants will stay in the vegetative growth stage Materials and Methods of the family, is a small and form a rosette under short daylighting and perennial herbaceous shrub 1 m tall and lower temperatures (Nishidate et al., 2012). Plant material and growth conditions. 1 m wide (Toaima et al., 2016; Vettori The formation of the rosette significantly Four commercial cultivars of Gypsophila et al., 2015). It is normally characterized by a affects the flower production of Gypsophila paniculata (‘My Pink’, ‘Million Stars’, rosette of grayish green basal leaves and paniculata because these rosette plants cannot ‘Cloudstar 8’, and ‘Cloudstar 5’) (Fig. 1) linear lanceolate from which the flower stems bloom. Therefore, for year-round produc- were selected for this study. ‘My Pink’ and propagate and end in mounds of branching tion of Gypsophila paniculata,specifictech- ‘Million Stars’ are the commercial cultivars stems covered by clouds of tiny white or pink niques such as artificial lighting and heating that were introduced by Danziger, a com- flowers (Atasxlar et al., 2009; Cronquist, are used to provide optimal light and tem- pany in Israel (Moshav Mishmar Hashiva). 1981). Gypsophila paniculata is a famous perature conditions. Although the light can However, ‘Cloudstar 8’ and ‘Cloudstar 5’ ornamental plant that is considered one of the be replaced by an LED source, artificial are specifically bred based on the environ- 10 best-selling cut flower worldwide heating is energy-consuming during winter. mental conditions of Kunming. The plant (Zvi et al., 2008). Because of its ornamen- To overcome this serious limitation and to seedlings were obtained from Yuxi Yunxing tal value, Gypsophila paniculata has been optimize flower production during winter, Biological Technology Co., Ltd. (Yunnan grown not only for flower arrangements but the application of growth regulators may province, China), and they were separately also as a perennial garden plant (Wang et al., offer an inexpensive and relatively simple planted in pots (diameter, 25 cm; height, 30 2013). method of enhancing flower production by cm) filled with commercial potting medium The flowering behavior of Gypsophila regulating the growth and development of (peat and perlite mixture). Then, all plants paniculata is strongly influenced by growth plants (Rameau et al., 2015). Gibberellic were grown in the greenhouse (without conditions, mainly daylength and temperature acid is considered essential for the develop- heating) during the natural photoperiod (Thakur et al., 2013). It has been reported that ment of stamens and petals (Elfving et al., (Table 1) at the experimental farm of 2011; Ni et al., 2015) because it uses the Yunnan Academy of Agricultural Sciences. response of the plant reproductive develop- Planting season and GA3 treatment. Seed- ment to environmental stresses, especially lings were continually planted on 1 July, 1 Received for publication 23 Apr. 2019. Accepted unfavorable temperature conditions (Liu Sept., and 1 Nov. to explore the seasonal for publication 23 Apr. 2019. et al., 2017; Wu et al., 2016). More specif- variations in growth and development. Ten Supported by the Science and Technology Program ically, under lower temperatures, gibberel- seedlings of each were grown during of Yunnan Province (No. 2016IA001) and the Key lin signaling produces the effects of warm each month. Two different GA3 treatments Research and Development (Agricultural field) temperatures, which are essential for the (four applications and eight applications) Project of Yunnan Science and Technology Pro- response to the long-day induction effects were applied to plants that were planted on gram (No. 2018BB010). We thank Dr. Shiyu Ma for assistance with the English language grammar (Lopez and Gonzalez, 2006). Therefore, 1 Nov.; four applications and eight applica- and syntax of this manuscript. gibberellic acid could promote the develop- tions of 125 mg/L GA3 were sprayed during 1 Corresponding authors. E-mail: snruanjiwei@ ment of flowers and help plants bloom under the entire growing season. The GA3 treat- 126.com or [email protected]. low temperatures. ments were started on 1 Dec. at a frequency

1370 HORTSCIENCE VOL. 54(8) AUGUST 2019 of once per week, and each treatment was multiple samples at a significance level of 5% was delayed. Consistent with this, the fresh used for 10 individual plants. (a = 0.05). weight and dry weight exhibited the same Data collection and statistical analysis. increases, but the flowering time was post- During the flowering period, the growth Results poned. From these results, we can conclude parameters, such as plant height, crown that Gypsophila paniculata is sensitive to the width, flowering time, and plant rosette rate, Seasonal variations in growth and devel- planting season, and that vegetative growth of each treatment were measured using a opment for Gypsophila paniculata. We con- will be prolonged when planting is performed ruler and vernier caliper. Then, the entire tinually planted seedlings for 3 months to during autumn and winter. However, seasonal individual plant was collected to measure the explore and simulate the effects of different sensitivity varies in different cultivars. ‘My fresh weight and dry weight using an elec- planting seasons on the growth and develop- Pink’ was the most sensitive to the planting tronic scale. These data were used to evaluate ment of Gypsophila paniculata during the season, exhibiting rosette rates of 20% and the effects of the planting season and GA3 natural photoperiod of a low-latitude and 80% when planted in September and Novem- treatment on the growth and development of high-altitude region. In general, different ber, respectively. ‘Million Stars’ was less each cultivar. Data analysis and statistics planting seasons had a significant impact on sensitive than ‘My Pink’, with a rosette rate were performed using Microsoft Excel 2016 the plant growth of four cultivars (Fig. 2). of only 10% when it was planted in Novem- (Microsoft Corporation) and Data Processing With the delayed planting time, the plant ber. Moreover, two cultivars, ‘Cloudstar 8’ System (Hangzhou Ruifeng Information Tech- height significantly increased, but the crown and ‘Cloudstar 5’, were not sensitive to the nology Co., Ltd., China) (Tang and Zhang, width decreased. This reflects the fact that planting season, indicating that they have 2013). A one-way analysis of variance with plants will continually undergo bolting and adapted to the environmental conditions of Tukey’s honestly significant difference post vegetative growth under low-temperature low-latitude and high-altitude regions; there- hoc test was used for the mean comparison of conditions; consequently, the flowering time fore, they could be planted during winter. These results suggest that different cultivars require different planting seasons, and that these planting seasons are determined by the genetic background of the cultivar. During the natural photoperiod in Kunm- ing, different planting seasons had significant influences on plant growth, such as extended vegetative growth and delayed flowering time. In the worst case, it caused plant rosettes for ‘My Pink’ and ‘Million Stars’, which was disastrous for flower producers. However, ‘Cloudstar 8’ and ‘Cloudstar 5’ were able to bloom and flower during the winter even though the flowering time was delayed. This could be acceptable to flower producers because the flower yield was also increased. Therefore, ‘Cloudstar 8’ and ‘Cloudstar 5’ could lead to more income for flower producers during winter, when the supply of other flowers is lacking. Effects of GA3 on the growth and develop- ment of Gypsophila paniculata. To overcome plant rosettes during autumn and winter, we applied the growth regulator GA3 to the plants that were planted on 1 Nov. Compared with the control, the plants showed increased plant height, crown width, fresh weight, and dry weight with the increased spray applications (Fig. 3). This indicated that GA3 could stimu- late and promote vegetative growth under low- temperature conditions. More specifically, eight applications of GA3 treatment not only had a greater impact on the fresh weight and dry weight of all cultivars but also could promote early flowering compared with the control. Four applications of GA3 treatment suppressed biomass accumulation in ‘Million Stars’ and ‘Cloudstar 5’, possibly because fewer GA3 Fig. 1. Four commercial cultivars of Gypsophila paniculata were used in this study: (A) Gypsophila treatments could promote early flowering and, paniculata ‘My Pink’; (B) Gypsophila paniculata ‘Million Stars’; (C) Gypsophila paniculata consequently, reduce vegetative growth. Fur- ‘Cloudstar 8’; and (D) Gypsophila paniculata ‘Cloudstar 5’. Each cultivar refers to a different thermore, GA3 also suppressed the occur- phenotype. Bar = 1 cm. rence of rosettes in ‘My Pink’ and ‘Million

Table 1. Average natural daylength and temperature of each month in Kunming. Month Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. Daylength (h) 10.78 11.31 12.02 12.75 13.36 13.66 13.51 12.98 12.29 11.56 10.94 10.63 Temperature ( C) 10.70 13.18 16.02 19.01 21.42 22.66 22.05 21.78 20.69 17.79 14.62 10.87 Data regarding the average natural daylength and temperature were observed from the detectors at the experimental farm at Yunnan Academy of Agricultural Sciences.

HORTSCIENCE VOL. 54(8) AUGUST 2019 1371 Fig. 2. Effects of different planting seasons on the growth and development of Gypsophila paniculata. Statistical significance was analyzed based on a one-way analysis of variance. P was calculated with Tukey’s honestly significant difference post hoc test (a = 0.05).

Stars’; it especially reduced the 40% and 80% ring with delayed planting time. Specifi- 5’, which has no sensitivity to the photope- rosette rates of ‘My Pink’ that occurred four cally, some cultivars showed significant riod. A natural photoperiod of only 11 h is applications and eight applications of GA3 sensitivity to planting seasons and generated provided from December to February, but treatment, respectively. This demonstrated rosettes when seedlings were planted in ‘Cloudstar 8’ and ‘Cloudstar 5’ are able to that GA3 treatments during low temperatures autumn and winter, such as ‘My Pink’ and flower, with little delay in flowering time. could relieve the rosette rate, which is impor- ‘Million Stars’. This was mainly caused by This difference may be caused by the ge- tant for the flower production of Gypsophila the low temperatures in winter, and GA3 netic background of different cultivars; paniculata. treatment was able to provide effective ‘Cloudstar 8’ and ‘Cloudstar 5’ are specif- improvements. Moreover, low temperatures ically bred based on the environmental Discussion are not the only limitation to the growth and conditions of Kunming. development of Gypsophila paniculate.The Using different quantities of GA3 applica- In this study, four cultivars of Gypsoph- photoperiod is an important factor for tions enhanced the plant height, width, and ila paniculata were planted during different growth because Gypsophila paniculata is a weight of Gypsophila paniculata compared months (July, September, and November) of long-day species. It has been reported that a with control, thus indicating that GA3 treat- the natural photoperiod. The results showed photoperiod of at least 14 h is needed for ment could effectively promote plant vegeta- that the general growth and development the flowering of Gypsophila paniculata tive growth during winter. More importantly, were affected by planting seasons, with a (Nishidate et al., 2012). However, this is GA3 treatment was able to prevent the occur- trend of extended vegetative growth occur- not the case for ‘Cloudstar 8’ and ‘Cloudstar rence of rosettes in ‘My Pink’ and ‘Million

1372 HORTSCIENCE VOL. 54(8) AUGUST 2019 Fig. 3. Effects of different GA3 spray times on the growth of Gypsophila paniculata. Statistical significance was analyzed based on a one-way analysis of variance. P was calculated with Tukey’s honestly significant difference post hoc test (a = 0.05).

Stars’. This demonstrated that GA3 treat- et al., 2004; Putterill and Laurie, 2004; Literature Cited ment could stimulate and promote plant Simpson, 2004). The molecular mechanisms Atasxlar, E., I.P._ Erkara, and S. Tokur. 2009. Pollen growth and development. Gibberellins are of gibberellins regulation could be partially morphology of some Gypsophila L.(Caryo- a type of high-performance and broad- explained by the regulation of the flower phyllaceae) species and its taxonomic value. spectrum plant growth regulator and critical meristem identity gene LEAFY and flower- Turk. J. Bot. 33:335–351. plant hormone (Hedden and Thomas, 2012; ing time gene SUPPRESSOR OF CON- Blazquez, M.A., R. Green, O. Nilsson, M.R. Patrick et al., 2009), functioning either from STANS 1 (Blazquez et al., 1998; Blazquez Sussman, and D. Weigel. 1998. Gibberel- the seedling stage to the maturity stage (Sun, et al., 1997; Mouhu et al., 2013; Tyagi et al., lins promote flowering of Arabidopsis by 2010) or from nutritional development to 2018). However, the molecular mechanisms activating LEAFY promoter. Plant Cell reproductive development (Eriksson et al., controlling the regulation of flowering in 10:791–800. 2006). According to the current study of the Gypsophila paniculata are not well-known Blazquez, M.A., L.N. Soowal, I. Lee, and D. Weigel. model plant Arabidopsis,floweringwas and require further study. Our research pro- 1997. LEAFY expression and flower initia- tion in Arabidopsis. Development 124:3835– controlled by the interaction between three vides a simple and efficient way to prevent 3844. different pathways (long-day pathway, au- rosettes when planting Gypsophila panicu- Boss, P.K., R.M. Bastow, J.S. Mylne, and C. Dean. tonomous pathway, and gibberellin path- lata during winter. This method could 2004. Multiple pathways in the decision to way), but the gibberellin pathway was the be applied during the flower production of flower: Enabling, promoting, and resetting. main regulator of floral induction (Boss Gypsophila paniculata. Plant Cell 16:S18–S31.

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