THE ROOTING OF ACTIVELY GROWING AND DORMANT LEAFY CUTTINGS IN RELATION TO ENDOGENOUS HORMONE LEVELS AND PHOTOPERIOD

Abstract

A series of poplar cuttings, Populus×robusta (Schneid.), excised at intervals during the summer showed a decline in rooting ability until mid‐August when cultured in long‐days. This was correlated with a decline in auxin at the RF of IAA. Leafy cuttings with growing apices rooted no better than dormant leafy cuttings when both were cultured in long days, and the bases of both types of cuttings possessed similar quantities of hormone at the RF of IAA. A bean hypocotyl bioassay of the ‘neutral’ ether fraction of an extract of terminal zones of poplar stems in August showed that the major root‐initiating hormone (RF 0.8 in 4:I, isopropanol: water) promoted no extension growth when assayed with wheat coleoptiles. Comparisons of the auxin levels at the base of July cuttings during the first 5 days after their excision showed an increase of auxin at the RF of IAA and of a neutral hormone near the solvent front. Copyright © 1972, Wiley Blackwell. All rights reserved