秃杉苗端离体培养的形态组织学研究

MORPHO-HISTOLOGICAL INVESTIGATION OF PLANTLET FORMATION IN VITRO IN TAIWANIA FLOUSIANA GAUSSEN

观察了10—12日龄秃杉(Taiwania flousiana Gaussen)苗端离体培养中不定芽和不定根的形态发生。不定芽可起源于苗端的表皮、表皮下1—2层细胞和周围区内的分生细胞,也可起源于子叶的近轴面,而以周围区为主。苗端不定芽以两侧周围区为中心,各自进行细胞分裂和分化,结果形成两个新的苗端生长点和叶原基,构成两个新的不定芽;子叶不定芽起源于近轴面表皮下1—2层细胞,这些细胞脱分化形成不定芽原基,但大多不能进一步发育,只有少数可发育为不定芽。嫩枝转入生根培养基后,不定根主要起源于叶隙薄壁细胞脱分化形成的不定根原基。此外,嫩枝中分化水平低的,如皮层、韧皮部、形成层区、髓射线的薄壁细胞几乎都可脱分化形成分生细胞团,但极少能发育为不定根。

Histological events during adventitious shoot formation in cultured shoot apex of 10-12- day-old seedlings and adventitious root formation in the elongated shoot of Taiwania flousiana Gaussen were examined.Cells of the peripheral subsurface layers of the shoot apex responded to cytokinin and divided into meristematic cells from which the shoot primordia were proliferated.A few bud primordia also originated from the epidermis and hypodermis of the adaxial surface of the cotyledon.The parenchyma of leaf gap of the shoots cultured in rooting medium dedifferentiated to regain the capacity of division and form adventitious root.Besi- des,cells that had relatively low potential of differentiation,such as the cortex parenchyma, pith ray,phloem parenchyma and cambium zone,albeit initiated to divide,but seldom formed root primordium.The origin of the adventitious roots in the leaf gap facilitated the establishment of the vascular connection between the shoot and root.