Effect of Ethephon on Easy Pot Freesia

Transcription

1 Effect of Ethephon on Easy Pot Freesia Ludmila Startek and Piotr Zurawik Agricultural University Department of Ornamental Plants Szczecin Poland Keywords: Popey, Suzy, Gompey, developmental stages, flowering, corm yield Abstract A series of experiments were conducted during June to December in 2 through 22, to evaluate the effects of ethephon (a source of ethylene) on the growth, decorative value and corm yields of three cultivars of genetically short freesia. Plant material consisted of the cultivars: Popey, Suzy and Gompey from the Dutch breeding firm Van Staaveren (Royal Van Zanten). Ethephon (Flordimex 42 SL) was applied at the rate of ml dm -3 (125-2 mg dm -3 ethephon). Prior to planting corms were soaked for 24 hours in Flordimex 42 SL solution at six concentrations. Neutralised sphagnum peat supplemented with Osmocote Plus was the growing medium. Five corms per pot (N 14) were planted and kept in a plastic tunnel without cooling during the summer. Ethephon delayed emergency, growth and flowering; the higher its concentration the stronger the effects. It also increased the firmness of leaves and caused intensive branching of plants. Depending on concentration, the number of inflorescences and their decorative value decreased with an increase in concentration. The coefficient for increases in corm numbers increased while the corms weights decreased. Ethephon at the rate of mg dm -3 slightly delayed flowering, improved and prolonged plant decorative value. In this case, there was also an increase in total number of corms, even doubled, although there was no effects on their total weight. INTRODUCTION Freesia, one of the most decorative and appreciated ornamental plants, is grown for cut flowers and also as a pot plant. The first, genetically short freesia plants, called Easy Pot were bred by the Dutch firm Van Staaveren, at present Royal van Zanten (Zurawik et al., 23). In Poland, pot freesia are still considered new plants and those on our market come from Holland (Startek et al., 2; Zurawik et al., 23). Freesia cultivation, both for cut and pot flowers, requires optimum conditions for plant growth and development i.e. proper temperature and moisture (Startek et al., 2, 22; Startek, 22). In the production of ornamental plants, including freesia, growth regulators such as ethylene may play a considerable part (Kawa-Miszczak et al., 1997). Ethylene may affect plant size, conformation, and the course of developmental stages, earliness and abundance of flowering (Imanishi, 1993; Shi et al., 1997; Lee et al., 1998; Mynett et al., 21). However, its effects depend on many factors, which should be taken into consideration. The aim of our experiments was to determine the effects of ethephon (the source of ethylene) on the course of developmental stages, vegetative and generative features, and the quality of Easy Pot freesia offspring corm yield. MATERIALS AND METHODS The experiments on three cultivars of Easy Pot freesia: Gompey, Popey and Suzy were conducted during June to December in In 2 and 21, the corms for the experiments were for 16 weeks before planting at 28 C at 8% relative humidity. In 22 the corms were prepared and stored at C at 5-6% relative humidity. Prior to storage and planting, corms were soaked in the following solutions: Proc. IX th Intl. Symp. on Flower Bulbs Eds.: H. Okubo, W.B. Miller and G.A. Chastagner Acta Hort. 673, ISHS

2 Kaptan 5 WP suspension at the concentration of 1.5%, Benlate 5 WP at the concentration.4% and Actelic EC at the concentration.1%. Directly before planting, dried corms were treated with ethephon (Flordimex 42 SL) at five concentrations: 125, 25,, 1, 2 mg dm -3. Corms soaked in water served as the control. These treatments took place in the dark room at 28-3 C and the corms were held for 24 hours in tightly closed containers. Immediately after the removal from the containers, 5 corms were planted into a 14 cm pots (1. dm 3 ). Naturalised sphagnum peat at ph 6.2, supplemented with 5 g Osmocote Plus 5-6 was used as the medium. Corms were placed in the pot 2-3 cm below the peat level and the pot edge. The pots were then placed on tables in a foil tunnel. During the summer there was no cooling and the temperature depended on the weather and ranged from 18-4 C. Heating started in mid-october, and the temperature was maintained between 4-1 C. Temperatures were recorded by means of thermohigrograph TZ 42. The experimental design was completely randomised. 18 experimental objects were examined in each experiment (3 cultivars x 6 ethephon concentrations). Each object consisted of twenty freesia corms, five corms per one pot. The course and length of developmental stages were estimated during a six-month period. In experiment 1 and 2 (2-21), stems and leaves were measured in vegetative stage and inflorescences and flowers in generative stage. After vegetation, the coefficients of weight increase and corm number increase, were calculated. In experiment 3 (22), only emergence was estimated since it was uneven and on some objects no emergence was observed during a six-month period. RESULTS AND DISCUSSION In all experiments, irrespective of the cultivar, the higher the ethephon concentration the more delayed and prolonged the emergence was. The control Suzy plants, in experiment 1 and 2 (years 2-21) emerged after 8 days on the average, Gompey after 9 days, and Popey after 1 days (Fig. 1). The lowest ethephon concentration (125 mg dm -3 ) delayed plant emergence by days and the delay caused by the highest concentration (2, mg dm -3 ) ranged from 24 days (in Gompey in 21) to 87 days (in Popey in 2). Depending on ethephon concentration, in all cultivars the vegetative stage was prolonged, flowering delayed or there was no vegetative stage. The effect of ethephon on the course of developmental stages depended also on the cultivar, but this was generally more pronounced in 21 than in 2. In 2 there was no generative stage in Popey after the application of 2, mg dm -3 ethephon, whereas in 21 neither of the cultivars under study started generative stage after treatment with 2, mg dm -3 and 1, mg dm -3 ethephon. Among the examined cultivars, Suzy had the earliest flowering, by days on the average. The differences between Popey and Gompey were less distinct and depended on the year and ethephon concentration. In the 22 experiment on the corms stored at C, control corms germinated unevenly, even up to 79 days depending on the cultivar. Similar to experiment 1, the earliest emergence was observed in Suzy, but after 2, mg dm -3 only 1% of corms germinated in experiment 2. The Gompey corms had the best emergence, 1% at the concentration of -25 mg dm -3 and 5% at the concentration of 2, mg dm -3. Popey was the most sensitive cultivar, since 125-2, mg dm -3 ethephon resulted in the total lack of emergence and corm rotting and pupation. According to Imanishi (1993), Shi et al. (1997) and Lee et al. (1998), ethylene not only ceases dormancy period but also accelerates vegetation and flowering. In our experiments ethephon, the source of ethylene, had the reverse effects. It did not break dormancy, but did delay emergence and the course of developmental stages. Similar results were obtained using ethephon in freesia cultivation for cut flowers (Mynett et al., 21). The literature shows that corm ethylene treatment stimulates an increase in the number of shoots per corm (Berghoef et al., 1986; Imanishi and Fortainier, 1983; Imanishi and Berghoef, 1986). In our studies ethephon also stimulated an increase in stem number. 618

3 Due to a considerable delay in emergence in all cultivars, a month after planting (July), only the control plants and those that had soaked in 125 and mg dm -3 of ethephon produced stems. New stems successively appeared during the next months. The first ones (1-2) usually turned yellow and died, the next ones developed properly. Most stems per one corm were obtained after 2 mg dm -3 of ethephon (Table 1). Irrespective of ethephon, in all cultivars the stem number depended on corm weight. The highest corm weight was found in Suzy in the experiment conducted in 2. Ethephon had a considerable effect on the plant height, conformation and appearance. The higher the concentration, the shorter the plants (more compact), the more intensive wax cover, and the shorter, wider and thicker the leaf blades. Similar changes were also recorded in the experiments on freesia cultivated for cut flowers (Mynett et al., 21). Growth regulators, including ethylene, affect freesia flowering period and the quality of inflorescences (Imanishi and Berghoef, 1986). In our studies it delayed and limited flowering. In the year 2, after the application of 2 mg dm -3, and 1 and 2 mg dm -3 in 21, none of the cultivars produced flowers. Both in the first and second year, significantly more flowers were found in the control freesia (Table 2). The number of flowers also decreased with increased ethephon concentration. Gompey always had the most flowers and its inflorescences were well branched, which had a positive effect on its decorative value as a pot plant. Ethephon shortened stems and lessened the number of inflorescence branches. According to the literature ethephon also effects the growth of gladiolus, increasing their number and simultaneously decreasing their weight (Kawa-Miszczak et al., 1997). Similar results were obtained in our experiments on freesia using ethephon. The greatest number of cormlets, but of lowest weight, was harvested after the application of 2 mg dm -3 i.e. the highest concentration in these studies (Table 3-4), and the cormlets were very small g. When they were stored at 28 C before planting, they developed properly but had poorer flowering in comparison with the control corms of higher weight. Taking into consideration both the corm weight and number, the best effects in comparison to the control group were obtained after the application of 25- mg dm -3. The experiments conducted by many authors indicate that ethylene decreases corm dormancy and accelerates vegetation and flowering. In our studies ethephon, which breaks down inside plant tissues releasing ethylene (Reid, 1992), had the reverse effects i.e. it did not break corm dormancy and delayed emergence and the course of developmental stages. Ethephon similarly to ethylene gas increased the number of stems per plant and the number of offspring corms. Literature Cited Berghoef, J., Zevenbergen, A.P. and Imanishi, H The effect of temperature and ethylene on dormancy of Freesia corms. Acta Hort. 177(2): Imanishi, H Freesia, The Physiology of Flower Bulbs. p In: A.A. De Hertogh and M. Le Nard (eds.), Elsevier Science Publishers, Amsterdam. Imanishi, H. and Berghoef, J Some factors affecting dormancy-breaking by ethylene in freesia corms. Acta Hort. 177: Imanishi, H. and Fortainier, E.J Effects of exposing freesia corms to ethylene or to smoke on dormancy-breaking and flowering. Scientia Hort. 18: Kawa-Miszczak, L., Wegrzynowicz-Lesiak, E. and Saniewski, M The positive effect of ethylene on ornamental bulbous and tuberous plants growth and development. (in Polish with English summary). Postepy Nauk Rol. 1: Lee, J.J., Jeong, J.S. and Kim, J.C Effects of high-temperature storage and ethylene on breaking dormancy of freesia corms. J. Korean Soc. Hort. Sci. 39(6): Mynett, K., Startek, L., Zurawik, P. and Ploszaj, B. 21. The effects of Gibrescol and Flordimex on the emergence and growth of freesia. Rocz. AR Pozn. (in Polish with English summary). CCCXXXII, Ogrodnictwo 33: Reid, M.S Ethylene in postharvest technology. University of California p

4 Shi, Y.M., Tao, Y.W., Qin, W.Y. and Fei, X.N Effects of chilling and plant growth regulators of freesia flowering. Acta Hort. Sinica 24(2): Startek, L. 22. Growth dynamics and decorative value of Easy Pot freesia depending on the growing conditions. Acta Hort. 57: Startek, L., Mynett, K. and Zurawik, P. 22. The effect of the method of cultivation on the development of freesia (Freesia Eckl. Ex Klatt). Acta Hort. 57: Startek, L., Zurawik, P., Rejent, J. and Dobrowolska, A. 2. The influence of temperature and storage period of corms on the development of potted freesia. (in Polish with English summary). Zesz. Nauk. Inst. Sad. i Kwiac. 7: Zurawik, P., Startek, L. and Salachna, P. 23. Growth, development and flowering in summer period of Easy Pot freesia cultivars. (in Polish with English summary). Zesz. Probl. Post. Nauk Rol. 491:

5 Tables Table 1. Stem number in Easy Pot freesia depending on cultivar, ethephon concentration and measurement time. Year Cultivar Ethephon (mg dm -3 ) Measurement time (month) July September December 2 Popey , , Suzy , , Gompey , , Popey , , Suzy , , Gompey , , no shoots 621

6 Table 2. Number of flowers per Easy Pot freesia depending on cultivar and ethephon concentration. Year Cultivar (O) Ethephon (R) (mg dm -3 ) Mean , 2, (O) 2 Popey Suzy Gompey Mean (R) LSD.5 O-1.53 R-2.31 R(O)-4. O(R) Popey Suzy Gompey Mean (R) LSD.5 O-1.84 R-2.34 RxO-r.n. 1 - no shoots Table 3. Coefficient of corm weight increase in Easy Pot freesia depending on cultivar and ethephon concentration. Year Cultivar (O) Ethephon (R) (mg dm -3 ) Mean , 2, (O) 2 Popey Suzy Gompey Mean (R) LSD.5 O-.163 R-.281 R(O)-.487 O(R) Popey Suzy Gompey Mean (R) LSD.5 O-.9 R-.156 R(O)-.271 O(R)-.221 Table 4. Coefficient of corm number increase in Easy Pot freesia depending on cultivar and ethephon concentration. Year Cultivar (O) Ethephon (R) (mg dm -3 ) Mean , 2, (O) 2 Popey Suzy Gompey Mean (R) LSD.5 O-r.n. R-.517 R(O)-.896 O(R) Popey Suzy Gompey Mean (R) LSD.5 O-.146 R-.253 RxO-r.n. 622

7 Figures [mg dm -3 ] Popey 21 Etephon Number of days [mg dm -3 ] Suzy 21 Etephon Number of days Gompey [mg dm -3 ] 2 21 Etephon Number of days vegetative stage generative stage Fig. 1. Length of Easy Pot freesia developmental stages depending on cultivar and ethephon concentration. 623