Study On Regeneration In Vitro Of Leaf In Haworthia Pilifera M.B.Bayer

In this experiment,the leaf regeneration of Haworthia pilifera M.B.Bayer,the genus Haworthia,the family Liliaceae was studied.The leaves of Haworthia pilifera M.B.Bayer were selected as explants and a complete set of leaf regeneration system was established through the induction,differentiation,green buds proliferation and rooting.Factors affecting the leaves regeneration were discussed,including hormone concentration and proportion,genotype,leaf maturity,placement and cutting methods.Then,the cell histological observation was performed on the differentiation of callus and green buds.The change of cell histology in the callus and green buds were revealed and the days of culture in the callus and green buds were determined to provide basis for selecting the appropriate radiation period.The optimal time for UV induction of callus was discussed.The main results of this experiment were as follows:1 The optimum induction medium for the induction and differentiation of callus and green buds was MS+BA1.0 mg/L+IBA0.1 mg/L.The induction rate of callus was 20.83%;The induction rate of green buds was 52.16%.The ‘Heiji' was the most highly induced genotype;The inner layers(from 1-2 layers inside and outside)were the optimum explants and the regeneration effect of inner layers was the best;The induction effect of the whole leaf was better than half leaf.The differentiation rate of basal leaves was higher than that of middle and upper;The placement method had no significant effect on green buds induction.The optimum multiplication medium was MS+BA2.0 mg/L+IBA0.2 mg/L and the proliferation coefficient was 3.24.The optimum rooting medium was IAA0.5 mg/L.The average rooting rate was93.10%.The average rooting numbers were 4.49,and the average root length was 2.21 cm.2 The morphology of 0-14 days explants in tissue culture was observed by paraffin method and the cell changes and characteristics of the species in the process of morphological construction were studied.The origin of the callus and green buds was mainly leaf epidermal cells and mesophyll parenchyma cells and the origin was polygenesis.The callus was the most active after 5 days.The callus began to differentiate after 13 days.The epidermis of leaves began to differentiate after 8 days.The leaf structure was observed through scanning electron microscope and the surface stomas of the far axial plane was more significant than that of the near axial plane.The surface stomas of basal leaves was more significant than that of middle and upper.3 According to the survival rate and differentiation rate,the appropriate irradiation time was 180 min.After ultraviolet radiation,the leaf color of green buds was shallow and the leaves appeared dark green streaks.The leaves were thick,and the green buds were low.