Effects Of Photoperiod And Polyamines On Characteristics Of Flower Bud Differentiation In Dendrobium Nobile

Dendrobium nobile is epiphyte of Orchidaceae Dendrobium, and it’s a newly-arised potted flower with a large potential market. The florescence of Dendrobium nobile is posterior, and it cotinues from February to April in normal conditions, so it can’t meet the market need of the New Year’s day and the Spring Festival. Flowering control is necessary to meet the market need, for that it can bring florescence forward and make more economic value. Tuning photoperiod artificially is frequently-used method, and it’s easy and without environmental pollution. In the experiment, firstly, it has studied on the effect of photoperiod on characteristics of flower buds differentiation of Dendrobium nobile. The differentiation processes of flower buds were researched by paraffin section method. On the basis of the morphology, there are four physiology indexes mensurated in the period of flower buds differentiation in different photoperiods, which includes the soluble sugar, soluble protein, POD and polyamines. Finally, this experiment has studied on the effect of exogenous polyamines on morphological characteristics of the flower bud differentiation in Dendrobium nobile in different photoperiods.The major results are summarized as follows:1. The effect of photoperiod on the morphological characteristics of flower buds differentiation in Dendrobium nobileThe differentiation process of flower buds of Dendrobium nobile ’V2’ could be divided into 7 phases:Initial differentiation phase, Inflorescence primordium differentiation phase, Bract primordium differentiation phase, Flower primordium differentiation phase, Sepal primordium differentiation phase, Petal primordium differentiation phase, Column and pollinia differentiation phase. The flower buds are very small in the initial differentiation phase. Cease growth buds almostly happen in flower primordium differentiation phase. Column and pollinia differentiation phase need more time than others. Dendrobium nobile ’V2’ is a facultative short day plant. The number Flower buds and flowers growing under short days treated is more than these plants which growing under long days. So that it can be seen that the short days treated treated is be propitious to to make flowers bigger. The bulbil numbers on the plants under the long days treated are more than the plants under the short days treated.2. The effects of photoperiod on physiological and biochemical charateristics of flower bud differentiation in Dendrobium nobileThe contents of soluble sugar in the leaves of Dendrobium nobile increased firstly and then decreased; the contents of soluble sugar under long days treated was higher than the plants under short days treated; The contents of soluble protein in the leaves reached a peak in initial differentiation phase, and then decreased slowly and finally increased again. The higher contents of soluble sugar and protein were propitious to the flower bud differentiation. The contents of POD in the leaves increased gradually and reached a peak in initial differentiation phase, then it decreased slowly and then increased, the time of reached a peak under short days treated was earier than the plants under long days treated. The contents of Put in the leaves reached a peak in initial differentiation phase, and the time of which reached a peak under short days treated turned forward of 10 days than the plants under long days treated. The higher contents of Put was propitious to to advance flower bud differentiation. The contents of Spd in the leaves exhibited an increasing tendency as a whole, and the accumulation of Spd was good for process successfully of flower bud differentiation, the contents of Spd under short days treated was higher than the plants under long days treated. The contents of Spm in the leaves decreased gradually in flower primordium differentiation phase then increased slowly, and the contents of Spm under short days treated was higher than the plants under long days treated.3. The effect of exogenous polyamines on morphological characteristics of flower bud differentiation in Dendrobium nobile in different photoperiodsUnder the short days treated, flower bud numbers, flower node numbers and flower numbers of the three varieties of Dendrobium nobile are the biggest after the treatment of Spd(1×10-4mol/L), in which the flower diameter is the biggest of other treatment. Under the short days treated, the first blooming of three varieties of Dendrobium nobile is the eariest after the treatment of Put(1×10-3mol/L), and the advanced time according to the time of the first peak of Put in the period of flower bud differentiation. Therefore, we summarized that higher contents of Put is propitious to to advance flower bud differentiation.