THE INFLUENCE OF BENZYLADENINE ON THE FLOWERING OF LIATRIS SPICATA L . ‘ ALBA ’ CULTIVATED FOR CUT FLOWERS IN AN UNHEATED PLASTIC TUNNEL AND IN THE FIELD

The study focused on the infl uence of benzyladenine (BA) on the fl owering of Liatris spicata L.‘Alba’ cultivated for two years in an unheated plastic tunnel and in the fi eld. Benzyladenine at a concentration of 0, 100, 200, 400 mg dm-3 was applied on the leaf twice during both years of the experiment. It was noted that cultivation of Liatris spicata L.’Alba’ in an unheated plastic tunnel leads to the growth of longer infl orescence stems with a bigger fresh weight and a larger number of primary shoots. However, in comparison with control plants, it decreases the yield of infl orescence stems in the fi rst and second year of the plants’ fl owering. It is benefi cial to apply benzyladenine at a concentration of 400 mg dm-3 on the leaves of Liatris spicata L. ‘Alba’ cultivated in an unheated plastic tunnel, because this treatment increases the number and fresh weight of infl orescence stems as well as the number of primary shoots in the fi rst and second year of the plants’ fl owering. It is also justifi ed to apply benzyladenine at a concentration of 400 mg dm-3 on Liatris spicata L. ‘Alba’ cultivated in the fi eld, as it leads to a greater number and fresh weight of infl orescence stems in the fi rst and second year of fl owering.


INTRODUCTION
Liatris spicata is a valuable ornamental plant.It grows long, straight and stiff infl orescence stems: 50 -120 cm long.On the stems there are fl owers gathered into baskets which form a dark pink, purple-red, violet, ivory or white spiky infl orescence.The baskets comprise of narrow ligulate fl owers which make them look fl uffy.Liatris spicata bears fl owers in an untypical way -from the top down to the bottom.Flowering lasts from July until the end of summer.
Liatris spicata is a constantly underestimated plant, but it is certainly worth a greater interest and attention.It is used in fl ower beds, where it integrates well with other plants.It can also be cultivated for cut fl owers.In bouquets it looks impressive in fl ower compositions as the main fl ower but also as the secondary decoration.
Traditionally, Liatris spicata is cultivated in the fi eld.In order to obtain earlier fl owering, fl owers of better quality, and bigger yield, there have been numerous attempts to cultivate it under a covering, predominantly in unheated plastic tunnel (H e t m a n and P o g r o s z e w s k a , 1997).
In order to obtain greater yield and better quality of infl orescence stems, the unheated plastic tunnel is successfully used to cultivate several species of ornamental plants (H e t m a n and P o g r o s z e w s k a , 1995; 1995a; 1996; 1996a The aim of the experiment was to study the infl uence of benzyladenine (BA), applied in various concentrations, on fl owering of Liatris spicata L. cultivated in an unheated plastic tunnel and in the fi eld.

MATERIALS AND METHODS
The research was conducted in 2004 and 2005.Liatris spicata plants were planted on 8 th October, 2003 in local soil in an unheated plastic tunnel and in the fi eld, in 1.5 m wide patches and in three rows with a distance of 0.40 x 0.48 m.The research was conducted in the fi rst and second year of the plants' fl owering.
Benzladenine (BA) was used at a concentration of: 0, 100, 200 and 400 mg dm -3 .Preparations were applied on the leaf twice and control plants were sprayed with distilled water.The fi rst treatment was given once the plants reached the height of 16-22 cm (using 40 ml of solution/plant) and the second one when the plants were about 40 cm high (using 60 ml of solution/plant).
Observations and measurement of the number and length of infl orescence stems, their fresh weight and the number of primary shoots were carried out during the whole experiment process.
The experiment was set up in the system of random block in 3 replicates, where a plot with 6 plants served as a replicate.The results were analyzed statistically by means of variance analysis for double classifi cations, evaluating the signifi cance of differences by means of Turkey's confi dence intervals at the level of signifi cance of α= 0.05.

RESULTS
A signifi cant difference in the number of infl orescence stems was noted in the fi rst year of Liatris spicata fl owering, depending on the cultivation place (Table 1).The plants cultivated in the unheated plastic tunnel grew 19.8% of infl orescence stems less than the plants in the fi eld.The plants cultivated in the fi eld and treated with benzyladenine at a concentration of 200 and 400 mg dm -3 produced infl orescence yield that was 11.7% (BA -200 mg dm -3 ) and 17.3% (BA -400 mg dm -3 ) higher than the yield of the control plants (not treated with the substance).The plants cultivated in the plastic tunnel and treated with BA at a concentration of 400 mg dm -3 produced infl orescence yield signifi cantly higher than the control (by 19.4%) The infl orescence stems of the plants cultivated in the unheated plastic tunnel in the 1 st year of the study were 10.4% longer than the stems of the plants cultivated in the fi eld (Tab.1).The plants cultivated in the plastic tunnel and treated with benzyladenine at a concentration of 400 mg dm -3 produced infl orescence stems 18.4% shorter than the control plants.It was observed that the plants cultivated in the tunnel had the tendency to produce shorter infl orescence stems, the bigger the concentration of benzyladenine was.
In the 1st year of fl owering, the plants cultivated in an unheated plastic tunnel produced stems with greater fresh weight than that of the plants cultivated in the fi eld (Tab.1).The difference was 19.4%.In all the tested concentrations, the bioregulator signifi cantly differentiated the fresh weight of Liatris spicata cultivated in the tunnel.Benzyladenine at a concentration of 400 mg dm -3 proved to be most desirable, as it also had a positive effect on fresh weight of stems in the fi eld, leading to value growth of the tested feature by 48% and 31.4% compared to the control plants.
The infl orescence stems of Liatris spicata cultivated in the plastic tunnel in the 1 st year of fl owering produced 1.5 times more primary shoots than the plants cultivated in the fi eld (Tab.1).Interaction of the studied factors was marked by the greatest number of primary shoots in the plants growing in the tunnel and treated with the substance at a concentration of 400 mg dm 3 .There were nearly 3 times more of them than in the control plants.In the fi eld, however, BA did not affect branching of Liatris spicata stems.
The age of the plants clearly infl uenced the yield of Liatris spicata infl orescences.The yield in the unheated plastic tunnel in the 2 nd year of fl owering was 107.3% greater than in the 1 st year.In the fi eld, it was 94.6% greater than in the fi rst year.
In the 2nd year of fl owering, the Liatris spicata plants cultivated in the plastic tunnel produced infl orescence yield 14.6% smaller than the yield of the plants cultivated in the fi eld (Tab.1).The plants treated with BA at all the concentrations, both in the fi eld and in the tunnel, produced more infl orescence stems than the control plants.The greatest yield of infl orescence stems was obtained by the application of benzyladenine at a concentration of 400 mg dm -3 .The treatment in the unheated plastic tunnel increased yield by 112.3%, whereas in the fi eld by 77.2% compared to the control plants.
It was observed in the 2nd year of Liatris spicata fl owering that the plants cultivated in the unheated plastic tunnel produced infl orescence stems 14.4% longer than the plants cultivated in the fi eld.A signifi cant effect of benzyladenine on the length of infl orescence stems of Liatris spicata in the 2 nd year of fl owering was observed after the application of BA -400 mg dm -3 to the plants in the fi eld.This treatment led to shortening of infl orescence stems length by 8.7% in comparison to the control plants.
The infl orescence stems of Liatris spicata cultivated in the unheated plastic tunnel in the second year of fl owering differed signifi cantly in the fresh weight from the stems of the plants cultivated in the fi eld (Tab.1).Those plants which grew in the plastic tunnel produced an infl orescence that had fresh weight 17% higher than the weight of an infl orescence of the plants cultivated in the fi eld.
The plants cultivated in the unheated plastic tunnel and treated with BA at all the concentrations produced infl orescence stems with greater fresh weight than that of the control plants.Infl orescence stems with the greatest fresh weight were obtained from the plants sprayed with benzyladenine at a concentration of 400 mg dm -3 .Those stems had 40.7% greater fresh weight than the weight of stems produced by the control plants.
The plants cultivated in the fi eld and treated with benzyladenine at a concentration of 400 mg dm -3 produced infl orescence stems with fresh weight 31.0%greater than the weight of the control plants' stems.
In the 2nd year of cultivation, the Liatris spicata plants cultivated in the plastic tunnel produced 63.6% more primary shoots than the plants in the fi eld (Tab.1).Interaction of the studied factors was marked with the greatest number of primary shoots in the Liatris spicata plants growing in the unheated plastic tunnel and treated with BA -400 mg dm -3 .There were over 3 times more of them than in the control plants.In the experiment, the infl orescence of Liatris spicata cultivated in a plastic tunnel had better quality, as estimated by the length and fresh weight of infl orescence stems than stems from fi eld cultivation.This confi rms the results of research on Liatris spicata by H e t m a n and P o g r o s z e w s k a (1997).A similar reaction to cultivation in an unheated plastic tunnel is observed in case of: Iris sibirica (P o g r o s z e w s k a , 1998), Molucella laevis L. (W r a g a , 1999) and Astilbe x arendsii Arends (P o g r o s z e w s k a and S a d k o ws k a , 2006).However, based on the research on Erigeron hybridus Bergm.'Dunkelste',S z c z e p a n i a k (2000) informs that despite rich fl owering, the plants in a plastic tunnel produced infl orescence stems of poor quality.

DISCUSSION
In our own research, the application of benzyladenine increased the number of infl orescence stems produced by Liatris spicata.A similar positive effect of benzyladenine on plants' fl owering was noted by B o yl e (1995) in the research on Easter cactus 'Crimson Giant' and by L e e et al. (1999) in experiments on Oncidium.
The plants of Liatris spicata treated with benzyladenine at a concentration of 400 mg•dm -3 produced infl orescence stems with a greater number of primary shoots than the control plants.

CONCLUSIONS
1. Cultivation of Liatris spicata L.'Alba' in an unheated plastic tunnel leads to the growth of longer infl orescence stems with a bigger fresh weight and a larger number of primary shoots.However, in comparison with control plants, it decreases the yield of infl orescence stems in the fi rst and second year of plant fl owering.2. It is benefi cial to apply benzyladenine at a concentration of 400 mg dm -3 on leaves of Liatris spicata cultivated in an unheated plastic tunnel, because this treatment increases the number and fresh weight of infl orescence stems as well as the number of primary shoots in the fi rst and second year of plant fl owering.3. It is also justifi ed to apply benzyladenine at a concentration of 400 mg dm -3 on Liatris spicata cultivated in the fi eld, as it leads to a greater number and fresh weight of infl orescence stems in the fi rst and second year of fl owering.
; P o g r o s z e w s k a , 1998; W r a g a , 1999; J a n o w s k a , 2000; S z c z e p a n i a k , 2000).Ornamental plants' fl owering and growth can also be infl uenced by means of growth regulators.Application of benzyladenine in some plants stimulates the development of side buds, which enhances their decorative value (Pogroszewska and F r ą c z e k , 2000; P o b u d k i e w i c z , 2005).Increasing the number of shoots, benzyladenine increases the size of plants such as for example Hosta (G a r n e r et al., 1997; K e e v e r and B r a s s , 1998; K o t a ń s k i et al. 2005).And it can be involved in the fl ower bud initiation process (G r z es i k and R u d n i c k i , 1989; Ł u k a s z e w s k a , 1991; D a v i e s et al. 1996; S u h , 1997; P o b u d k i e w i c z , 2006).BA affects fl owers' morphological features (K a w a -M i s z c z a k et al. 1992; S a n i e w s k i et al. 1997).
This experiment shows that plants cultivated in an unheated plastic tunnel produce a smaller yield than plants cultivated in the open fi eld, which confi rms the results obtained by H e t m a n and P o g r o s z e ws k a (1996) who claimed that cultivation in a plastic tunnel decreases the yield of Liatris spicata.Similar effects were observed by P o g r o s z e w s k a and S a dk o w s k a (2006) in a research on Astilbe x arendsii Arends.Depending on the species, plants can react differently to cultivation in an unheated plastic tunnel.P o g r o s z e w s k a ' s research (1998) on Iris sibirica and Hetman and P o g r o s z e w s k a ' s research (1996) on fl owering of Helleborus x hybridus hort.prove that cultivation in an unheated plastic tunnel increases plants' yield.Similar results were obtained by J an o w s k a (2000) and J a n o w s k a and S c h r o e t e r (2001).The authors claimed that the infl orescence yield of Dianthus barbatus cultivated in a tunnel was greater than the yield of plants cultivated in the fi eld.These observations are also confi rmed by Puczel and W a źb i ń s k a (2003) in the research on Craspedia globosa, and by W r a g a (1999) in the research on Molucella laevis L.
A similar reaction of plants to benzyladenine was noted by B e s s l e r (1997), who obtained a greater number of side branching due to benzyladenine in Tillandsia, and by P o b u d k i e w i c z (2005), who showed that the application of BA on the leaf improves growth of Dianthus caryophyllus L. of Colorado Majestic Mountain group.Results obtained in our own research are not consistent with the results of research by W a n g and B o o g h e r (1987) on Syngonium podophyllum Schott.'White Butterfl y', in which even the concentration of 2000 mg dm -3 did not have a positive effect on this feature.In all the studies conducted, the plants treated with benzyladenine at a concentration of 400 mg dm 3 produced shorter infl orescence stems than the control plants.Similarly, K i m and O k u b o (1996) inform about the shortening of Lablab purpureus stems, in comparison to the control, under the infl uence of benzyladenine.Analogical results were obtained by K i m et al. (2000) in the research on Doritaenopsis 'Happy Valentine' and by P o b u d k i e w i c z (2005) in the research on pot carnation.
The effect of benzyladenine on morphological features of infl orescence stems of Liatris spicata L. 'Alba'.Means followed by the same letters are not signifi cantly different at α=0.05 level of probability.Means of each year were compared separately. *