ABSTRACT OF THE PHD THESIS The entitled Research Regarding the Influence of Culture Technology upon the Growth, Development and Flower Induction in the Tuberose (Polyanthes tuberosa L.) approaches technological aspects regarding the culture of the tuberose in the central part of Transylvania, where these flower plants do not get cultural conditions at optimal parameters. The subject of the is in the framework of general preoccupation, in the domain of floriculture, for increasing production capacity per area and, at the same time, to decrease the expenses/product, by developing and perfecting some efficient, low cost methods in order to attain these objectives. The goal of the research that represents the subject of this was the contribution to the optimization of the culture conditions for species Polyanthes tuberosa and to elaborate a suitable technology that should allow the cultivation of this flower species on larger areas in the center of Transylvania, using cheap and easily accessible materials, for obtaining much higher flowering rates and far higher yields of potentially flowering replacement bulbs. The main objectives pursued during the practical research were: the study of the reaction of the tuberoses cultured in vegetation vessels, in 6 variants of organic substrate: a 1 - the soil of the experimental field a 2 50 % neutral peat + 50 % soil a 3-30 % neutral peat + 30 % manure + 40 % soil a 4 25 % neutral peat + 40 % manure + 15 % sand + 20 % soil a 5 50 % manure + 50 % soil a 6 75 % manure + 25 % sand establishing the optimal diameter of potentially flowering tuberose bulbs, which should ensure the maximization of flowering rate; establishing the categories of bulbs, regarding their diameter, which should ensure the obtaining of the highest number of potentially flowering replacement bulbs ( 25-1 -
mm). establishing the influence of bulb size and culture substrate upon bulb multiplication rate; establishing the efficiency of the mulching system (mulching with black polyethylene foil, red polyethylene foil and yellow polyethylene foil) as compared to classical culture in non-mulched soil. increasing the profitability per area of tuberose culture by establishing the optimal fertilization level, at minimal costs per product unit; establishing the influence of the culture system and fertilization level upon the multiplication rate of the bulbs. These objectives were approached by organizing two series of bifactorial experiments for a period of three years (2007-2009), set up in randomized blocks with three repetitions. The results were processed statistically by the method of the analysis of variance, using the method of multiple comparisons. The research was carried out in the research field of the Laboratory of Floriculture in the framework of the Fruit Research Station, situated in the city of Cluj-Napoca. The first experiment was carried out as a series of bifactorial experiments, having in view the influence of the culture substrate, that of the planted bulbs diameter and the interaction of these two experimental factors upon the vegetative morphological characteristics and the productivity of tuberoses (the number of bulbs/plant and the number of bulbs with the diameter 25 mm/plant). For the flowering rate as well as for the ornamental morphological characteristics of the plants it was considered as useless to present and discuss the experimental results as belonging to a series of bifactorial experiments, because in this case only the culture substrate had influence upon these characteristics, in the flowered plants obtained from a single type of bulbs (those with the diameter of 25 mm). Therefore it was preferred to transfer the data in a monofactorial system, as a series of experiments for three years, the significance of the differences being established exclusively based on the DL, calculated with the help of the variance of the interaction (s 2 Vxyears). - 2 -
The second experiment was set up as a series of bifactorial experiments for all the characteristics taken into study and we were having in view the influence of the culture system (mulching) and the level of fertilization upon the vegetative and ornamental morphological characteristics and the productivity of tuberose plants. After the studies and the analysis of experimental results a series of conclusions and recommendations were formulated, which contain the answers to some questions regarding the possibilities and techniques for the culture of Polyanthes tuberosa, as well as the effect of some culture factors upon the growth and development of the plants grown in pots and directly in the field, in the central zone of Transylvania. The maximal values regarding average bulb weight were obtained as a result of the interaction between substrate a 4 (25 % neutral peat + 40 % manure + 15 % sand + 20 % soil) and the diameter of the planted bulbs, 25 mm in the case of the plants that had not flowered (7.5 g/bulb). The average diameter of the bulbs obtained had superior values as a result of the interaction between substrate a 4 (25 % neutral peat + 40 % manure + 15 % sand + 20 % soil), being of 14.2 mm, a 3 (30 % neutral peat + 30 % manure + 40 % soil), being of 13.8 mm, and the planted bulbs' diameter of 25 mm of the plants that had not flowered and as a result of the interaction between substrate a 4 (25 % neutral peat + 40 % manure + 15 % sand + 20 % soil) and the planted bulbs' diameter of 20 mm (13.8 mm). The superior level of soluble dry matter appears as a result of the interaction between substrate a 4 (25 % neutral peat + 40 % manure + 15 % sand + 20 % soil), 29.5 5 dry matter, with the diameter of the planted bulbs, 25 mm from the plants that had not flowered. The average number of plantlets regenerated per bulb and the average number of leaves/plant gave superior values on substrate a 3 (30 % neutral peat + 30 % manure + 40 % soil) in the plants obtained from 25 mm bulbs that did not have flower induction and flowering, the difference being significantly superior as compared to all the combinations of the two experimental factors. The highest number of replacement bulbs (18.4 19.1 bulbs/plant) appears in the interaction between substrates a 2 (50% neutral peat + 50% soil), a 5 (50% manure + 50% soil) - 3 -
and a 6 (75% manure + 25% sand) with the diameter of the planted bulbs, 25 mm, in the case of the plants that had not flowered. The highest number of bulbs with the diameter 25 mm appears at the interaction between substrate a 4 (25 % neutral peat + 40 % manure + 15 % sand + 20 % soil) with the the diameter of the planted bulbs, 25 mm, in the case of the plants that had not flowered (3.6 bulbs with the diameter of 25 mm /plant). The flowering rate of the plants is higher in the case of substrates a 5 (50 % manure + 50 % soil), a 3 (30 % neutral peat + 30 % manure + 40 % soil) and a 4 (25 % neutral peat + 40 % manure + 15 % sand + 20 % soil), on which high and very high flowering rates were obtained (68.1% - 96.1%). Flower stem length and inflorescence length were the highest on substrate a 4 (25 % neutral peat + 40 % manure + 15 % sand + 20 % soil), 102.8 cm, with a distinctly significant positive difference as compared to the control variant a 1 (the soil of the experimental field), where it was of 76.7 cm. The substrates a 5 (50% manure + 50% soil) and a 3 (30 % neutral peat + 30 % manure + 40 % soil) had significantly positive differences as compared to the control a 1 (the soil of the experimental field), the values for this characteristic being very close (95.8 96.1 cm). For flower stem diameter, the culture substrate had a significantly positive influence only in the case of variant a 4 (25 % neutral peat + 40 % manure + 15 % sand + 20 % soil), the influence of all the other substrate compositions was insignificant. The upper limit for the average number of flowers/inflorescence was achieved on substrate a 4 (25 % neutral peat + 40 % manure + 15 % sand + 20 % soil), 28.0 flowers/inflorescence, at a very significantly positive difference as compared to the control variant, a 1 (the soil of the experimental field), 21.0 flowers/inflorescence. For flower length and diameter the most recommended composition is that of the culture substrates a 4 (25 % neutral peat + 40 % manure + 15 % sand + 20 % soil) and a 3 (30 % neutral peat + 30 % manure + 40 % soil), where the maximal values were registered, both culture substrates being situated at very significantly positive differences as compared to the control variant. Substrate a 6 (75 % manure + 25 % sand) yielded the lowest values for flower - 4 -
diameter (5.0 cm), at a very significantly negative difference as compared to the control variant a 1 (the soil of the experimental field), 5.4 cm. For the majority of vegetative and ornamental morphological characteristics as well as for productivity in tuberoses, the best technological variant for mulching and fertilization is mulching with black polyethylene foil on soil with organo-mineral fertilization, at significant differences as compared to all the other variants. The variant with organo-mineral fertilization and mulched with black polyethylene foil yielded the highest values for flower stem diameter (10.3 mm), at an insignificant difference as compared to the variant fertilized only organically and mulched with black polyethylene foil (9,1 mm). The best technological variant for mulching and fertilization for tuberoses for the number of flowers/inflorescence was applying with black polyethylene foil for mulching on soil with organo-mineral fertilization, which increases this characteristic by 13 flowers/inflorescence as compared to the non-mulched soil fertilized only organically. For the morphological characteristics of the bulbs, the diameter of the bulbs selected for planting had the greatest importance, the effect of the culture substrate and the effect of the interaction between the two factors being low (2%-16% from the total influence of the factors). The average number of plantlets regenerated/bulb as well as the average number of leaves/plant were influenced by the diameter of the planted bulbs (54 %), the culture substrate (23%) as well as by the interaction of the two factors (20%). The most powerful effect upon the number of bulbs/plant was given by the planted bulbs' diameter (60 % of the total effects) and the interaction between the factors in the years of experimentation (32 %). The culture substrate had a small effect (6 %) upon this characteristic. For all the characteristics that were studied, the levels of fertilization and mulching had the greatest importance (35%-47%) for ensuring superior values for these characteristics, whereas the interaction between the factors in the years of experimentation had a very low importance (1%-8%), which proved that the two factors and the years of experimentation did - 5 -
not contribute to the obtaining of superior results regarding the studied characteristics. The importance of the effects of mulching, fertilization level and the interaction between these factors in the years of experimentation regarding average inflorescence length is directly proportional with the effects of the factors and the interaction between the factors upon the average number of flowers/inflorescence, their values being very close. The importance of the effects of mulching, fertilization level and the interaction between these factors in the years of experimentation regarding average flower length is directly proportional with the effects of the factors and the interaction between the factors upon average flower diameter, their values being almost identical. Based upon the experimental results, we recommend to the tuberose cultivators to apply differentiated technologies for planting, fertilization and mulching, according to the precise purpose of the respective culture. In the case in which the culture is done only for the purpose of the ornamental effect of the plants, we recommend, in the conditions of the center of Transylvania, to plant only the bulbs with diameters 25 mm. The plants formed from such bulbs have the tendency to flower in a high proportion, having vigorous inflorescences with a high number of flowers/inflorescence. For the culture of tuberoses done for the purpose of producing planting material (bulbs), we recommend the planting of bulbs with diameters of 15-25 mm. The plants grown from bulbs with diameters of 15-20 mm usually do not flower but they produce a large number of large replacement bulbs, which are potentially flowering. The organo-mineral fertilization with manure 20 t/ha + NPK 15:15:15 complex fertilizer, (as a 0.2 % solution applied at 10 day intervals) represents a sure method for obtaining vigorous tuberose plants, with high flowering rates. At this fertilization level the plants that do not flower generate a large number of large replacement bulbs (20-25 mm in diameter). The mulching of the tuberose culture with black polyethylene foil can bring important increases in bulb production and bulb sizes and for the obtaining of plants with high flowering rates and increased decorative effect. - 6 -