DYNAMICS OF GROWTH AND FLOWERING OF THE WAX BEGONIA (BEGONIA SEMPERFLORENS LINK ET OTTO) TREATED WITH FOLIAR- AND SOIL-APPLIED RETARDANTS

Anita Schroeter-Zakrzewska¹, Marek Jerzy^2
1 Department of Ornamental Plants, University of Life Sciences in Poznań, Poland
² Department of Ornamental Plants, Agricultural University of Poznan, Poland

ABSTRACT

The experiment was carried out in the years 2001-2002. Young plants of the wax begonia 'Eureka Bronze Rose' were grown in the greenhouse in pots using a peat substrate mixed with sand. B-Nine, Cycocel and Topflor were applied once or twice at 14-day intervals, through leaves and the soil. In May the plants were bedded and every month their height was measured and the number of buds and flowers counted. The dynamics of growth and flowering of the bedded plants was observed. The strongest and longest-lasting growth retardant was Topflor, both foliar- and soil-applied. Soil-applied B-Nine and Cycocel were found to have no adverse effect on the number of buds and flowers.

Key words: Begonia semperflorens Link et Otto, retardants, growth, flowering.

INTRODUCTION

One of effective methods for improving the quality of bedding plants is the application of growth retardants. They allow the grower to obtain shorter, more compact plants, often flowering more abundantly. It should be remembered, however, that the response of individual species, or even cultivars, to retardants can vary [5].

Retardants are usually foliar-applied, but it is also possible to apply them through the soil. The research conducted by Jerzy and Schroeter [4] showed that for the French marigold cultivar 'Jumbo Golden Yellow' the strongest and longest-lasting growth retardants were B-Nine and Cycocel applied at concentrations of 0.15% and 0.2% as well as 0.2% and 0.3%, respectively. In turn, Topflor at concentrations of 0.025% and 0.05% was the weakest retardant. Foliar-applied Cycocel and Topflor were found to have produced no adverse effect on the number of buds and flowers developed by the plants. Only B-Nine was observed to have impaired the flowering of the French marigold. Soil application of those retardants stunted the growth of young marigold plants. B-Nine, soil-applied twice during plant production at a concentration of 0.2% and Cycocel at 0.3% applied once or twice, had a positive effect on the flowering of the French marigold.

The aim of the present study was to learn how retardants applied during the production of young plants affected the growth and flowering of the wax begonia cultivar 'Eureka Bronze Rose' growing in the ground.

MATERIAL AND METHODS

In the years 2001-2002 two experiments were carried out in the greenhouse and in the ground in which an assessment was made of the effect of foliar- and soil-applied retardants B-Nine, Cycocel and Topflor on the growth and flowering of the wax begonia (Begonia semperflorens Link et Otto) 'Eureka Bronze Rose'.

Young plants were planted in 9-cm pots and grown in the greenhouse. Peat substrate was used mixed with sand at 3:1 by volume. The medium was enriched with 2 g of a slow-release mixed fertiliser Osmocote 3-4 M and 0.5 g of brown Superba per 1 dm³. As top dressing, every 10 days 0.1% solutions of mixed fertilisers were applied: yellow Kristalon (13:40:13), blue Kristalon (19:6:20), and white Kristalon (15:5:30), 50 ml per pot. Once, at the beginning of culture, all the plants were fed 0.1% lime saltpetre.

In the first experiment conducted from March to July 2001, retardants were foliar-applied. The plants were first treated with them on 10 April 2001. The next treatment was given on 24 April 2001. The retardants included B-Nine 85 SP at concentrations of 0.15 and 0.2%, containing daminozide at concentrations of 127.5 mg l^-1 and 170 mg l^-1, respectively; Cycocel 460 SL at concentrations of 0.2 and 0.3%, containing chloromequat at concentrations of 920 mg l^-1 and 1380 mg l^-1, respectively; and Topflor 015 SL at concentrations of 0.025 and 0.05%, containing flurprimidol at concentrations of 3.79 mg l^-1 and 7.58 mg l^-1, respectively. The experiment schedule is presented in table 1.

The experiment consisted of 15 combinations (retardant × its application variant) with 30 replications in each, one plant being a replication.

Retardant-treated plants were transplanted to the ground on 8 May 2001 at a 20×20 cm spacing. Every 14 days measurements were taken of their height as well as the number of buds and flowers.

The results of the last measurement in the greenhouse and the last measurement in the ground were processed statistically using the analysis of variance, and the means obtained were grouped using Duncan's test at the α = 0.05 significance level.

The other experiment was conducted from March to September 2002. After a month of culture, the plants were watered with retardant solutions. Use was made of B-Nine at a concentration of 0.2% containing daminozide at a concentration of 170 mg l^-1; Cycocel 460 SL at a concentration of 0.15% chloromequat at a concentration of 690 mg l^-1; and Topflor 015 SL at a concentration of 0.025 containing flurprimidol at a concentration of 3.79 mg l^-1, 50 ml per pot. Two weeks later variant 2 plants were watered again.

Retardant-treated plants were transplanted to the ground on 15 May 2002 at a 20×20 cm spacing. The experiment consisted of 9 combinations (retardant x its application variant) with 15 replications in each, one plant being a replication.

Biometric measurements of the plants' height and the number of buds and flowers were carried out every month from May to September.

The results were processed statistically using the analysis of variance, and the means were grouped using Duncan's test at the α = 0.05 significance level.

RESULTS

Dynamics of growth and flowering of plants grown from trans-plants treated with foliar-applied retardants

All variants of retardant treatment turned out to inhibit growth in comparison with the control. Topflor had the strongest retarding effect in all aspects, while B-Nine proved to be the least effective.

Significant differences in the height of control plants and those treated in various ways with B-Nine, Cycocel and Topflor recorded on 8 May in the greenhouse persisted until 30 July, i.e. the end of observation of plants growing in the ground (table 2).

Out of the three retardants applied, Topflor had the strongest and longest-lasting effect on the 'Eureka Bronze Rose' cultivar of wax begonia, especially in variants III and IV of the experiment, after two applications at a concentration of 0.025% and two applications at concentrations of 0.025% and 0.05%, respectively. The plants treated with this retardant were considerably shorter than control plants until the end of time of observation in the ground.

Cycocel had the strongest effect in variant I of retardation consisting in one application of this retardant at a concentration of 0.1%. B-Nine, in turn, was the most effective in variants I and II of retardation when it was applied once and twice, respectively, at a concentration of 0.15% and in variant III when it was applied twice at concentrations of 0.15% and 0.2%.

The plants retarded with B-Nine, Cycocel and Topflor did not attain the height of control plants by the time the experiment finished, i.e. the end of July (figure 1).

The statistical analysis of the results obtained during the last measurement in the greenhouse showed there to be no significant differences between the action of B-Nine and Cycocel. Significantly fewer buds and flowers were observed in plants sprayed twice with Topflor at a concentration of 0.025% (variant II), twice at 0.025% and 0.05% (variant III) and twice at 0.05% (variant IV); and in those treated with Cycocel (variant IV) when the preparation was applied twice at a concentration of 0.15%. Also, no significant differences were recorded between the number of buds and flowers of control plants and that of plants treated in various ways with B-Nine (table 3).

At the close of observation, on 30 July, B-Nine-treated plants flowered less abundantly than the control. Significant differences in the number of buds and flowers of control plants and the number of buds and flowers of those retarded in various ways with Cycocel and Topflor recorded on 8 May when transplanting them to the ground persisted until the end of observation of plants flowering in the ground (figure 2).

The statistical analysis of the results obtained during the last measurement on 30 July showed there to be no significant differences between the action of B-Nine and Cycocel.

Topflor was the growth retardant that had the strongest and longest-lasting effect on the wax begonia 'Eureka Bronze Rose'.

The plants treated with this preparation formed much fewer buds and flowers than control plants, especially after two applications at a concentration of 0.025%, two applications at concentrations of 0.025% and 0.05% (II, III), and two applications at a higher concentration of 0.05% in variant IV of treatment.

Dynamics of growth and flowering of plants grown from trans-plants treated with soil-applied retardants

Differences between the action of the retardants observed in May persisted to the end of observation of plants in the ground.

Out of the retardants applied, Topflor had the strongest and longest-lasting effect. In comparison with control plants, those treated with this retardant were considerably shorter. This effect persisted until the end of observation in the ground.

Cycocel had no significant effect on plant height (table 4). The statistical analysis for the last glasshouse measurement and that in the ground did not show significant differences between the height of control plants and those treated with this preparation. An exception was variant I with a single application of the retardant at a concentration of 0.15% in which the plants were 35.2% shorter than the control.

B-Nine turned out to be the least effective. In all the variants plants treated with this retardant were taller than the control until the end of observation (figure 3).

The statistical analysis carried out for the May glasshouse measurement revealed differences in the action of B-Nine, Cycocel and Topflor (table 5). Topflor proved to be the least effective. Plants watered once and twice with a solution of this preparation at a concentration of 0.025% flowered poorly and developed fewer buds and flowers, by 83.0% and 81.5%, respectively, than control plants. This strong effect of the retardant persisted to the end of observation of soil-grown plants. At the start of cultivation, 21.2% fewer buds and flowers than on control plants also formed on those that were twice given a solution of Cycocel at a concentration of 0.15%. In the case of this preparation, between June and August there was a marked increase in the number of buds and flowers in plants treated with it once at a concentration of 0.15%. Also in August, plants watered with a B-Nine solution at a concentration of 0.2% flowered more abundantly (figure 4).

The statistical analysis carried out for the last measurement of plants in the ground in September did not reveal any differences in the action of the three retardants.

DISCUSSION

The effects of retardants are temporary and reversible. They depend not only on the concentration of the preparation and way of its application, but also on the susceptibility of the species treated [1].

Flurprimidol can be both foliar- and soil-applied. Both modes of application have a strong growth-retarding effect [7, 9].

In the experiment described, both ways of application of Topflor, which contains flurprimidol, resulted in strong growth inhibition in wax begonia. Irrespective of the dose and mode of application, the plants treated with this retardant flowered poorly in comparison with the control. At the close of the experiment, they were shorter and had fewer flowers than the control. Similar results were obtained by Schroeter and Janowska [8].

The adverse effect of Topflor on flowering intensity has been corroborated by experiments with pansies [9]. The wax begonia is a plant susceptible to flurprimidol contained in this preparation. In his instructions for growers, Oscheck [6] suggests that to control growth in the wax begonia it is best to use Topflor once at a concentration of 0.025%.

The second, foliar-applied retardant, Cycocel, had a weaker growth inhibiting effect than Topflor. This weaker effect of Cycocel has also been confirmed by Startek [9]. Plants treated with this preparation were shorter than the control. The growth inhibiting effect persisted until the end of observation.

When soil-applied, however, this retardant had no effect on the height of plants. Towards the end of observation, the treated plants did not differ from the control with the exception of those given one application at a concentration of 0.15%. In this variant the plants watered with a solution of Cycocel were taller than the control.

Both soil and foliar application of Cycocel had and adverse effect on the flowering of begonia. This finding has been corroborated by Schroeter and Janowska [8].

B-Nine is mainly recommended as a foliar because its effectiveness in soil application, according to Jankiewicz [2], is low. The research described has confirmed it. Soil-applied B-Nine produced an effect opposite to the one intended, because it stimulated growth in the plants. The effect persisted throughout the cultivation period. Equally ineffective was Alar (the present trade name of B-Nine) in the cultivation of strelitzia; applied through leaves and soil, it stimulated the plants' growth [3].

Soil-applied B-Nine had no effect on the flowering of begonia. Throughout the cultivation period, plants treated with this retardant did not differ from the control. Its foliar application, however, proved to be more effective.

The plants sprayed with a B-Nine solution were shorter than the control throughout the cultivation period. This differs from the findings of Startek [9], who maintains that B-Nine has a weak and brief effect. Her opinion is shared by Latimer [5], who claims that the effect of daminozide on plant height lasts a mere 5-7 weeks from planting them in the ground.

Foliar application of B-Nine resulted in the plants forming a smaller number of buds and flowers. This is what Treder et al. [10] also found in Rudbeckia.v

CONCLUSIONS

1. Foliar-applied retardants inhibited the growth of young plants, especially after two applications of Topflor at a concentration of 0.05%, B-Nine at a concentration of 0.2%, and Cycocel at a concentration of 0.15%, with Topflor having the strongest retarding effect. Soil application of Cycocel and Topflor also inhibited the growth of young plants. B-Nine proved to be a retardant stimulating plant growth.

2. Soil- and foliar-applied Topflor brought about a reduction in the number of buds and flowers.

3. The growth of planta in the ground was retarded the strongest and the longest by Topflor applied both through leaves and soil.

4. Soil-applied Topflor had an adverse effect on the flowering of begonia. No such adverse effect on the number of buds and flowers was observed after treatment with B-Nine and Cycocel.

REFERENCES

1. Barrett J. E., Nell T. A., 1989. Comparison of paclobutrazol and uniconazole on floriculture crops. Acta Hortic. 251, 275-280.

2. Evers G., 1987. Die Anwendung von bioregulatoren im Zirpflanzenbau. Paul Parey Verlag. Berlin und Hamburg.

3. Hetman J., Pogroszewska E., Szot P., 1994. Możliwość zmniejszania rozmiarów strelicji poprzez zastosowanie retardantów. II. Wpływ retardantów na wzrost wegetatywny strelicji (Strelitzia reginae Banks) [The possibility of Strelitzia size reduction using growth retardants. II. Efect of retardants on vegetative growth of Strelitzia reginae Banks]. Hodowla Roślin i Nasiennictwo 4-5, 56-62 [in Polish].

4. Jerzy M., Schroeter A., 2004. Dynamika wzrostu i kwitnienia aksamitki rozpierzchłej (Tagetes patula L.) uprawianej z rozsady poddanej działaniu retardantów stosowanych dolistnie i doglebowo [The dynamics of growth and flowering of marigold cultivated from trans-plants treated with different retardants used to leaves and directly to peat-substrate] Acta Sci. Pol. Hortorum Cultus 3(1), 11-23 [in Polish].

5. Latimer J. G., 1991. Growth retardants affect landscape performance of zinia, impatiens and marigold. Hort. Sci. 26, 557-560.

6. Oschek W., 2001. Stauchen und Hemmen. Deutscher Gartenbau 6, 35-38.

7. Pobudkiewicz A., 1995. Retardanty wzrostu zarejestrowane w Polsce do stosowania w uprawie chryzantem wielkokwiatowych (Dendranhema grandiflora Tzvelev) [Growth regulators registered in Poland for chrysanthemums]. Wiadomości Chryzantemowe 19, 45-47 [in Polish].

8. Schroeter A., Janowska B., 2003. Wpływ retardantów stosowanych dolistnie na jakość rozsady begonii stale kwitnącej (Begonia semperflorens Link et Otto) i petunii ogrodowej (Petunia hybrida Vilm.) [The influence of different retardants applied as a leaf spray on quality of Begonia semperflorens and Petunia hybrida]. Zesz. Probl. Post. Nauk Rol. 491, 229-236 [in Polish].

9. Startek L., 2001.Wpływ retardantów wzrostu oraz miejsca zimowania na cechy morfologiczne bratka ogrodowego (Viola × wittrockiana Gams.) [The effects of growth retardants, place of growing and wintering on morphological traits of garden pansy]. Wyd. AR w Szczecinie Rozprawy 201, 72 [in Polish].

10. Treder J., Matysiak B., Nowak J., 1998. Wpływ temperatury nocy i B-Nine na wzrost i kwitnienie Rudbeckia hirta `Toto´ [Effect of night temperature and B-Nine on growth and flowering of Rudbeckia hirta `Toto´]. Zesz. Nauk. AR w Krakowie 57, 785-789 [in Polish].