The development of cuttings of the Washington navel orange to the stage of fruit set. I. The development of the rooted cutting

Abstract

The development of rooted cuttings of the Washington Navel orange through two cycles of growth is described, and the effects of phosphorus nutrition and the relative value of nitrate and ammonium as sources of nitrogen are assessed. Alternation of shoot and root development over the period of the experiment was observed. There appeared to be no build up of dry matter reserves in the plant tops before new shoot initiation, but rather a rhythmic distribution between root and shoot of the dry matter assimilated. The initiation of new shoots was followed by a rapid increase in leaf area, by an increase in dry matter per unit leaf area, by a rapid increase in whole plant dry weight, and by higher growth rates. In this latter respect, the behaviour of this woody perennial contrasts with the normal growth pattern of annuals, where the growth indices tend to fall with time. Phosphorus shortage delayed plant development, so leading to lower dry weight values in all plant parts. No differences in growth due to nitrate or ammonium as sources of nitrogen could be detected.