Effect of Chilling, Benzyloaminopurine and Abscisic Acid on Development and Cell Constituents of in vitro Cultured Apple Buds from Dormant Trees

Abstract

Summary Single apple buds excised from dormant trees were cultured in vitro at 4°C for 30 weeks, on a medium either without growth regulators or supplied with 5 × 10 -6 M BA or 10 -4 M ABA. The cells of quiescent buds were small with a large, centrally situated nucleus. They were characterized by the absence of a large, central vacuole and they were full of starch bodies. No mitoses were found. After 30 weeks of culture, the water content and dry weight of the control buds increased, and they achieved bursting stage. Cells of the leaf primordia and pith (axis) enlarged distinctly. Cytoplasm and a small nucleus moved to the cell walls due to vacuolization of the cell centre. The cells contained only single starch grains. Mitotic figures occurred only occasionally. As compared with the control, mesophyll and pith cells of BA-treated buds were larger and the number of mitoses was somewhat higher. No other striking differences between the cell constituents of the control and BA-treated groups were found. The most specific effect of ABA appears to be suppression of pith (axis) cell growth. Starch depletion and degree of vacuolization were similar to that in the control cells. No mitosis was found in the meristematic region of ABA-treated buds.