FLOWERING DYNAMICS OF PEACH-LEAVED BELLFLOWER ( CAMPANULA PERSICIFOLIA L . ) ‘ ALBA ’ TREATED WITH BIOREGULATORS , GROWN IN AN UNHEATED PLASTIC TUNNEL AND IN FIELD

The effect of BA, GA3 and BA+GA3 on fl owering of peach-leaved bellfl ower (Campanula persicifolia L.) ‘Alba’, grown in an unheated plastic tunnel or in open fi eld, was investigated. Bioregulators at the following applications: 0, 100, 200, 400 mg x dm-3, were applied foliarly twice. It has been found that the cultivation of peach-leaved bellfl ower in an unheated plastic tunnel accelerates fl owering of plants by about 2 – 3 weeks, compared to open fi eld cultivation, in the fi rst and second year of fl owering of plants. It is advisable to apply gibberellic acid at a concentration of 400 mg x dm-3 in plastic tunnel cultivation of bellfl ower and at a concentration of 200 mg x dm-3 in fi eld cultivation, since this treatment accelerates fl owering by 2 – 9 days. It is recommended that gibberellic acid should be applied at a concentration of 400 mg x dm-3, which extends the fl owering period of peach-leaved bellfl ower grown in a plastic tunnel by 6 – 13 days. When peach-leaved bellfl ower is grown in an unheated plastic tunnel, full fl owering is predicted to occur in the fi rst or second week from the beginning of fl owering of plants. When bellfl ower is grown in open fi eld, full bloom of infl orescences is expected in the second week of fl owering of plants. Irrespective of the type of substance applied in both years of cultivation, in the unheated plastic tunnel the largest amount of infl orescences was ready for cutting in the fi rst decade of June, and in the fi eld in the second decade of June.


INTRODUCTION
One of the most ornamental species of perennial bellfl owers is peach-leaved bellfl ower (Campanula persicifolia L.).It is used not only in garden plantings, but also for cut fl ower cultivation.Bellfl ower produces large, light blue, less frequently white fl owers.Both infl orescence stems, reaching 30 -90 cm, and single fl owers are used by fl orists.1992).
Flowering of ornamental plants can be accelerated, without large expenditures, by using an unheated plastic tunnel.In our climate, ornamental plants are grown in unheated plastic tunnels from March to October, and even the beginning of November (L i s i e c k a et al. 1993).An unheated plastic tunnel is used for cultivation of many ornamental plant species in order to obtain earlier crops of infl orescence shoots (H e t m a n and P o g r o s z e w s k a , 1996a; 1997; S z c z e p a n i a k , 2000a).
The aim of the present experiment was to investigate the effects of benzyladenine (BA) and gibberellic acid (GA 3 ), applied at different concentrations, on the fl owering pattern of peach-leaved bellfl ower (Campanula persicifolia L.) grown in an unheated plastic tunnel and in fi eld.

MATERIALS AND METHODS
The experiment was conducted in the years 2004 and 2005.The object of the study was peach-leaved bellfl ower plants (Campanula persicifolia L.) 'Alba' planted in October 2003 in native soil in an unheated plastic tunnel and in fi eld, on 1.5 m wide patches in three rows.The investigations were carried out in the fi rst and second year of fl owering of plants.
Benzyladenine, gibberellic acid and benzyladenine + gibberellic acid were applied at the following concentrations: 0, 100, 200 and 400 mg x dm -3 (of each substance).Bioregulators were applied foliarly twice, and control plants were treated with distilled water.The plants, both those growing in the fi eld and in the tunnel, were treated with the formulation (at an amount of 40 ml of solution per plant) for the fi rst time when they reached a height of 16 -20 cm.The second spraying took place when the plants reached a height of about 40 cm (60 ml of solution was used per plant).The bellfl ower plants, both in the fi eld and in the tunnel, were systematically fertilised and irrigated.
During the experiment, observations of the fl owering dynamics of the plants were carried out.The date of beginning of fl owering (the fi rst developing infl orescences in each combination), full fl owering (the date on which the largest amount of infl orescence shoots reached commercial maturity) as well as the date of end of fl owering (the last infl orescences cut) were recorded.The percentage share of fl owering infl orescence shoots cut at three-day intervals in the total number of fl owering infl orescences in a given combination was determined.Infl orescence shoots were cut after the opening of the fi rst three fl owers in an infl orescence.
Thermal conditions in 2004, both in the open fi eld and in the unheated plastic tunnel, were less favourable for the growth of peach-leaved bellfl ower than in 2005 (Tab.1).In the fi eld, in 2004 mean monthly temperatures in May and June were lower than longterm means.In 2005 mean monthly temperature in May did not differ from the long-term mean, and in June it was lower by 1°C.The highest temperature was recorded in the 3rd decade of June in 2004, and in 2005 in the 3rd decade of May.In the plastic tunnel, mean monthly temperatures in May and June, that is, in the period of bellfl ower fl owering, in both years of the experiment, were higher than in the fi eld by about 4°C up to about 6°C, respectively.In 2004 the highest temperature was recorded in the 2nd decade of June, and in 2005 -in the 1st decade of June.

RESULTS AND DISCUSSION
The cultivation of peach-leaved bellfl ower (Campanula persicifolia L.) 'Alba' in the unheated plastic tunnel allowed obtaining fl owering infl orescence shoots 2 -3 weeks earlier compared to fi eld cul-tivation, in both years of fl owering of the plants.The fi rst infl orescence shoots of bellfl ower in the unheated plastic tunnel were cut on 19 May (1st year) and 25 May (2nd year).In the fi eld, the fi rst fl owering infl orescence shoots were ready for cutting on 9 June (1st year) and 6 June (2nd year) (Tab.2).
As reported by Va n de W i e l (1989), the use of a plastic tunnel accelerates fl owering of Campanula glomerata, C. medium, C. persicifolia, which is confi rmed by the results of the present study.According to S z c z e p a n i a k (2000b), the cultivation of clustered bellfl ower (Campanula glomerata) and peach-leaved bellfl ower (C.persicifolia) in a plastic tunnel accelerates fl owering by 2 weeks.In an experiment on Chinese peony (Paeonia lactifl ora Pall.), H e t m a n and Pogroszewska (1996b) found that fl owers could be harvested 2 -3 weeks earlier than in fi eld.H e t m a n and P o g r o s z e w s k a (1996a) and P o g r o s z e w s k a (1998), when investigating the usefulness of an unheated plastic tunnel for the cultivation of certain perennial plants, found that the use of the plastic tunnel accelerated fl owering of Lenten rose (Helleborus x hybridus) by 12 -23 days and fl owering of Siberian iris (Iris sibirica) by 1 -3 weeks compared to fi eld cultivation.Dianthus barbatus plants under unheated plastic bloomed 4 -8 days earlier than those grown in fi eld (J a n o w s k a and S c h r o e t e r , 2001).An unheated plastic tunnel is also used with success for the cultivation of Aquilegia x hybrida, Anemone coronaria, Dicentra spectabilis, Doronicum caucasicum, Primula elatior, Tanacetum coccineum, Trollins x hybridus (B a c h , 1989).
In the present experiment, the application of gibberellic acid accelerated fl owering of the peach- leaved bellfl ower plants.In the fi rst year of fl owering, the bellfl ower plants treated with gibberellic acid at a concentration of GA 3 -400 mg x dm -3 were the fi rst to bloom in the unheated plastic tunnel (19 May), whereas in the fi eld those also treated with gibberellic acid, but at a concentration of GA -200 mg x dm -3 (9 June).The application of gibberellic acid at these concentrations accelerated fl owering of the plants by 9 days in the tunnel and by 2 days in the fi eld compared to the control plants (Tab.2).
The obtained results are similar to the results of a study of T r e d e r et al. (1999) on the acceleration of fl owering of cyclamen using gibberellic acid.Similar results were obtained by L e N a r d and D e H e r t o g h (1993) in their study on tulip.However, data obtained in the present study are not consistent with the results of an experiment conducted by F ar o o q i et al. (1994) in which the application of gibberellic acid delayed fl owering of roses.
In the fi rst year of the present experiment, the date of full fl owering of the bellfl ower plants grown in the plastic tunnel and treated with GA 3 was dependent on the concentration of the bioregulator (Tab.2).In the control plants and those sprayed with GA 3 -100 mg x dm -3 , the largest amount of infl orescences was ready for cutting, respectively: in the middle and at the end of the 2nd week of fl owering of the plants in these combinations, in the plants treated with GA 3 -200 mg x dm -3 -in the middle of the 2nd week of fl owering of the plants treated with gibberellic acid at this concentration, and in the case of GA 3 -400 mg x dm -3 -at the end of the 3rd week of fl owering of the plants in this combination (Tab.3).In the fi eld, full bloom of infl o-rescences of the plants infl uenced by GA 3 at all concentrations, as well as of the control plants, occurred in the 2nd week of their fl owering.
Benzyladenine did not cause earlier fl owering of the plants.In the 1st year of the study, the plants treated with benzyladenine started fl owering on the same date as the control plants: 28 May (tunnel) and 11 June (fi eld) (Tab.2).A study of S a n i e w s k i and K a w a -M i s z c z a k (1992) proves that benzyladenine sometimes even delays fl owering of plants.
In the 1st year of the study, the plants growing in the plastic tunnel and treated with BA -100 mg x dm -3 and BA -200 mg x dm -3 fl owered quite evenly.Full fl owering of the plants subjected to the effect of BA -400 mg x dm -3 was noted in the 2nd week of fl owering of the tunnel-grown plants treated with this formulation, similarly to the control plants (Tab.4).In the fi eld, the plants treated with BA at all concentrations, analogously to the control plants, produced the largest amount of infl orescences mature for harvesting in the 2nd week of fl owering of the plants in each combination.

Control
GA 3 100 mgxdm -3 GA3 200 mgxdm -3 GA3 400 mgxdm The effect of BA on the fl owering dynamics of peach-leaved bellfl ower (Campanula persicifolia L.) 'Alba' grown in an unheated plastic tunnel and in fi eld in the 1st year of fl owering.
Table 5 The effect of BA+GA 3 on the fl owering dynamics of peach-leaved bellfl ower (Campanula persicifolia L.) 'Alba' grown in an unheated plastic tunnel and in fi eld in the 1st year of fl owering.The application of benzyladenine in combination with gibberellic acid, in the 1st year of fl owering of the plants, similarly to benzyladenine alone, did not accelerate fl owering of bellfl ower, and in the case of BA+GA 3 -200 mg x dm -3 , it even delayed fl owering by 3 days (tunnel) and by 2 days (fi eld) (Tab.2).

Date of observation
In the 1st year of fl owering of the plants, in the plastic tunnel-grown plants sprayed with BA+GA 3 at all concentrations, similarly to the control plants, the largest amount of infl orescences was ready for cutting in the 2nd week of fl owering of the plants in these combinations.In the fi eld, full bloom of infl orescences in those plants in which BA+GA 3 was applied at all concentrations was noted in the 1st week of their fl owering (Tab.5).
The applied bioregulators differentiated the length of bellfl ower fl owering period.In the fi rst year of the present experiment, the plants growing in the unheated plastic tunnel and treated with GA 3 -400 mg x dm -3 were characterised by the longest fl owering period (30 days).In the fi eld, the longest fl owering duration was noted in the plants sprayed with GA 3 -200 mg x dm -3 (16 days).The control plants fl owered shorter: in the plastic tunnel 17 days, in the fi eld 11 days.
In the second year of fl owering, as in the fi rst year, gibberellic acid at the same concentrations accelerated fl owering of the studied species' plants.In the plastic tunnel, the application of GA 3 -400 mg x dm -3 accelerated fl owering by 3 days (25 May), and in the fi eld, the application of GA 3 -200 mg x dm -3 -by 4 days (6 June) compared to the control plants (Tab.2).
In the second year, fl owering of the plants which were treated with GA 3 was more even compared to the fi rst year.Full fl owering of the plants treated with this bioregulator at all concentrations, in the plastic tunnel, fell on the end of the fi rst week or the beginning of the second week of fl owering of the plants in each combination.In the control, the largest amount of infl orescences was ready for cutting at the beginning of the second week of fl owering of the plants in this combination.In the fi eld, full bloom of infl orescences of the plants treated with GA 3 -0, 100, 200 and 400 mg x dm -3 , similarly to the control plants, occurred in the 2nd week of their fl owering (Tab.6).
In the unheated plastic tunnel, the plants in which benzyladenine was applied, fl owered in the second year even 1 day later (29 May) than the control plants (28 May).In the fi eld, they fl owered on the same day as the plants in the control treatment (10 June) (Tab.2).
In the second year of the study, the largest amount of infl orescences mature for cutting in the bellfl ower plants grown in the tunnel and treated with BA -100 mg x dm -3 , as in the control treatment, was noted in the 2nd week of fl owering of the plants in these combinations, and in the plants infl uenced by BA -200 and 400 mg x dm -3 -at the end of the fi rst week of their fl owering.In the fi eld, full fl owering of the plants sprayed with benzyladenine at all concentrations, likewise in the control plants, occurred in the second week of their fl owering (Tab.7).
In the second year of the experiment, both in the tunnel and in the fi eld, the plants treated with BA+GA 3 at all concentrations did not accelerate fl owering of the plants, similarly to the fi rst year of the study (Tab.2).
In the second year of the present experiment, in the unheated tunnel, full fl owering of the plants treated Table 6 The effect of GA 3 on the fl owering dynamics of peach-leaved bellfl ower (Campanula persicifolia L.) 'Alba' grown in an unheated plastic tunnel and in fi eld in the 2nd year of fl owering.

Number of developed infl orescences (%)
Control GA 3 100 mgxdm -3 GA 3 200 mgxdm -3 GA 3 400 mgxdm with BA+GA 3 at all concentrations took place at the end of the fi rst week of their fl owering.In the control plants, which fl owered most abundantly on a similar date, it was the beginning of the second week of their fl owering.In the fi eld, infl orescences of the plants subjected to the effect of BA+GA 3 at all concentrations, as in the control plants, matured for cutting in the largest number in the second week of their fl owering (Tab.8).
It should be stressed that, in both years of peachleaved bellfl ower cultivation in the plastic tunnel, the largest amount of infl orescences was cut in the 1st decade of June.In 2004 it was the second or third week from the beginning of fl owering of the plants in each combination, and in 2005 (which was slightly warmer) -the fi rst week in most cases.The date of full fl owering was associated with high temperature prevailing in the tunnel at that time and it suggests the studied species' sensitivity to thermal conditions.In the fi eld, the largest amount of infl orescences reached commercial maturity in the second decade of June and in both years of the study, it was in most cases the second week of fl owering of the plants in each combination.
In the second year of the study, the fl owering period of the plants depended both on the place of cultivation and the formulation applied.In the unheated plastic tunnel, the plants treated with GA 3 -200 mg x dm -3 and 400 mg x dm -3 fl owered the longest (19 days) -6 days longer than the untreated plants.In the open fi eld, the plants subjected to the effect of BA -200 mg x dm -3 were characterised by the longest fl owering period (18 days) -8 days longer than the fl owering period of the control plants (Tab.2).

CONCLUSIONS
1.The cultivation of peach-leaved bellfl ower (Campanula persicifolia L.) 'Alba' in an unheated plastic tunnel accelerates fl owering of plants by about 2 -3 weeks, compared to open fi eld cultivation, in the fi rst and second year of fl owering of plants.2. It is advisable to apply gibberellic acid at a concentration of 400 mg x dm -3 in bellfl ower cultivation in a plastic tunnel and at a concentration of 200 mg x dm -3 in fi eld cultivation, since this treatment accelerates fl owering by 2 -9 days.3. It is recommended that gibberellic acid should be applied at a concentration of 400 mg x dm -3 , which extends the fl owering period of peach-leaved bellfl ower grown in a plastic tunnel by 6 -13 days.4. When peach-leaved bellfl ower is grown in an unheated plastic tunnel, full fl owering is predicted to occur in the fi rst or second week from the beginning of fl owering of plants.When bellfl ower is grown in open fi eld, full bloom of infl orescences is expected in the 2nd week of fl owering of plants.
5. Irrespective of the type of substance applied in both years of cultivation, in the unheated plastic tunnel, the largest amount of infl orescences was ready for cutting in the fi rst decade of June, and in the fi eld -in the second decade of June.
The fl owering date of plants can be affected by applying plant bioregulators.Gibberellic acid (L e N a r d and D e H e r t o g h , 1993; J a n k i e w i c z , 1997; T r e d e r et al. 1999) or benzyladenine (K os t e n y u k et al. 1999) may cause earlier fl owering.However, benzyladenine sometimes delays fl owering of plants (S a n i e w s k i and K a w a -M i s z c z a k , Meteorological data based on measurements of the Meteorological Station of the University of Life Sciences, Lublin-Felin, made during the growing period of peach-leaved bellfl ower (Campanula persicifolia L.) 'Alba' in the years of study2004-2005.

Table 2
Characteristics of fl owering of peach-leaved bellfl ower (Campanula persicifolia L.) 'Alba' grown in an unheated plastic tunnel and in fi eld, subjected to the effect of bioregulators.

Table 3
The effect of GA 3 on the fl owering dynamics of peach-leaved bellfl ower (Campanula persicifolia L.) 'Alba' grown in an unheated plastic tunnel and in fi eld in the 1st year of fl owering.

Table 4
The effect of BA on the fl owering dynamics of peach-leaved bellfl ower (Campanula persicifolia L.) 'Alba' grown in an unheated plastic tunnel and in fi eld in the 2nd year of fl owering.The effect of BA+GA 3 on the fl owering dynamics of peach-leaved bellfl ower (Campanula persicifolia L.) 'Alba' grown in an unheated plastic tunnel and in fi eld in the 2nd year of fl owering.