Study On Morphological And Physiological Evolution Of Floral Bud Differentiation In Tulip

Two different tulip cultivars, Tulipa gesneriana L. cv.'Judith Leyster'and'Big Smile', were adopted in the experiment. The course of flower bud differentiation was observed by the method of paraffin section and the changes of water content, carbohydrate content, soluble protein content and enzymes activity were measured during flower bud differentiation. Lastly, small tubers (6⁸ cm round diameter) of tulip'Big Smile'were used to study the induction of flowering by 6-Benzylaminopurine (6-BA) and Paclobutrazol (PP₃₃₃). The experiment results were as follows:(1) The flower bud differentiation was initiated from mid June, and triangular swollen gynoecium was formed in early August. The process could be divided into five phases: undifferentiation stage, outer petal differentiation stage, inner petal differentiation stage, stamen differentiation stage, and pistil differentiation stage.(2) The top of flower buds inflated gradually into a dome-shape from the initial flat-shape, then started to become flatter and wider in the later stage of perianth differentiation, and finally showed a depression when the stamen differentiation occurred. In terms of changes in the external growth of flower bud, it grew much faster in the late stage than in the early stage of differentiation. The results showed that the flower bud differentiation of Tulip in Yangling is not only started earlier but also lasted longer than that in other place.(3) The amounts of carbohydrate during the bud differentiation showed a similar tendency among the two cultivars. Along with the decrease of the water content, the contents of the total soluble sugar and protein increased at the beginning, reaching to the peaks in the outer petal differentiation stage then began to decline. The amylase activity increased to a stable level during bud differentiation, while the change of starch content exhibited a little fluctuation. The POD activation was still fairly low but in creased and then decreased during the later period of flower bud differentiation.(4) It was the marker of the initiation of tulip flower bud morphological differentiation that soluble sugar content and amylase activity of the scales increased together. The primary source of nutrient in the flower bud differentiation periods is the inner scales relative to the outer scales. (5) The flower bud size and flower formation rates of small tubers of tulip are influenced to various extent by the different treatments of 6-BA and PP₃₃₃. Among those treatments,the treatment four (200 mg/L 6-BA+200 mg/L PP₃₃₃) got the best result,And, while hormone treatments is effective for the flower bud formation rates of big tulip tubers, the effect for the flower formation rates is lower.