Effect of nitrogen nutrition of stock plants ofJusticia gendarussaL. on the rooting of cuttings

Abstract

SummaryThe effect of the nitrogen nutrition of stock plants of Justicia gendarussa L. on the rooting of cuttings was studied in sand culture under high, medium and low levels of nitrogen.Nitrogen starvation induced rooting. Exogenous application of the auxins IAA (indol-3yl-acetic acid), IBA (indol-3yl-butyric acid) and NAA (naphth-lyl-acetic acid) greatly increased the rooting response of cuttings from-stock plants grown with small amounts of nitrogen.The root-promoting effect of a low nitrogen supply was associated with a retardation of growth in the stock plants from which the cuttings were made. High C/N (total available carbohydrates/total nitrogen) and P/N (total phosphorus/total nitrogen) ratios increased anthocyanin pigmentation in the shoot, and increased rooting cofactor activity in the tissues of cuttings. The phenolic compounds, ferulic acid, p-hydroxybenzoic acid and p-coumaric acid were present in the shoots of all three nutritional treatments and acted as important cofactors in the cuttings. In general, rooting cofactor activity was inversely related to nitrogen supply and the activity was highest under low nitrogen.The cuttings taken from plants grown under different levels of nitrogen interacted differentially with the exogenously applied auxins.