Experimental Studies of the Shoot Apical Meristem of Seed Plants. II. Morphological and Cytochemical Effects of Kinetin Applied to the Exposed Meristem of Pinus Elliottii

Abstract

Treating shoot apical meristems of Pinus elliottii seedlings with 1.5 μg kinetin results in bud scale formation and the onset of dormancy. IAA and GA produce no morphogenetic effects. According to cytochemical analyses, levels of ribonucleic acid (RNA) in kinetin-treated meristems exceed controls through the sixth day following treatment, during which time unsaturated lipids fall sharply below control values. Rapid declines in RNA by day eight, when cytoplasmic protein may also be at a relatively low concentration, coincide with the first appearance of bud scales, signaling the onset of dormancy in kinetin-treated meristems. Changes in concentration of RNA and lipid (and possibly protein) suggest that kinetin may effect nucleus-based events and/or membranes in the cytoplasm in the apical meristem. These effects may be related to the subsequent development of bud scales in the subapical region and to the onset of dormancy throughout the shoot tip. The central mother cell zone is not metabolically quiescent in the vegetative shoot apical meristem of Pinus seedlings.