Effect of temperature, light intensity and growth regulators on propagation of Ansellia Africana from cuttings

摘要

Ansellia africana?(Orchidaceae) is an important endangered medicinal plant species of South Africa which has been heavily exploited in recent years. Experiments were conducted in growth rooms at different temperatures (16, 26, 36°C) and in a nursery at different light intensities induced by shade cloth densities (200, 400, 600, 800 μmol m-2?s-1?light) at the University of Zululand, South Africa. Mature?A. africana?plants were cut into two lengths, the top leafy shoot and the bottom part with roots (10 – 15 cm in length, 3 - 8 mm diameter). The top leafy or leafless cuttings were used in all the experiments. Bud formation and rooting competence of cuttings were compared by growing cuttings treated with solutions of varying?naphthaleneacetic acid?(NAA) and kinetin concentrations in river sand. Three types of cuttings were used: a) mature cuttings with both green leaves and an inflorescence, b) mature cuttings with yellow leaves (or leafless) and an inflorescence, and c) young cuttings with green leaves but no inflorescence. The lowest percentage death was recorded in cuttings with both green leaves and an inflorescence in the growth room (10%) and nursery (5%), respectively. The same type of cuttings gave significantly higher (P < 0.05) percentage bud formation in the incubator (18%) and nursery (37%), respectively. NAA was effective in root initiation when applied after bud break. The best results for root number, root length and root dry weight were achieved at NAA concentration of 1 or 2 mg l-1. Optimum conditions for bud formation were temperature of 36°C, light intensity of 200 - 400 μmol m-2?s-1?and kinetin concentration of 1 or 2 mg l-1. A maximum value of 57% was recorded for bud formation in this study.