Root Initiation in Cuttings of<i>Pinus radiata</i>Seedlings

Abstract

Adventitious root initiation in hypocotyls of Pinus radiata D. Don consists of three distinct phases. In the pre-initiative phase, following selection of the cuttings, no histological changes are observed. The initiative phase begins with swelling of a single parenchymatous cell, the meristematic locus. Distinct cytoplasmic changes within the meristematic locus are followed by cytoplasmic migration and asymmetric division in the surrounding cortical or peripheral cells. The third, or post-initiative, phase includes continued division of derivatives of the peripheral cells to form meristemoids which subsequently differentiate into root primordia.