Changes in water potential and its components during shoot formation in tobacco callus

Addition of plant growth regulators (5 nM NAA and 5μM BAP) to a defined basal medium stimulated adventitious bud formation of Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) cotyledon explants in culture. Cytoplasmic soluble proteins synthesized during early stages of adventitious bud formation were analyzed by electrophoresis of ³H- and ¹⁴C-leucine labeled proteins on SDS polyacrylamide gels. Increased synthesis of low molecular weight proteins (16,000 to 20,000 daltons) was detected after 2 days in culture and reached a maximal level at day 4. When cotyledon explants cultured on bud medium for 2 days were transferred to callus medium (which suppressed adventitious bud formation), suppression of the synthesis of low molecular weight proteins was also observed, suggesting that these proteins may be associated with early stages of adventitious bud formation.