THE EFFECTS OF GROWTH RETARDANTS, HUMIDITY AND LIGHTING AT STAGE III ON STAGE IV OF MICROPROPAGATION IN CHRYSANTHEMUM AND ROSE

The use of transplantation plugs to protect roots, the inclusion in the culture medium of growth retardants to reduce endogenous gibberellins and the use of culture vessels that maintain a relatively dry atmosphere, lead to a significant reduction in wilting of in vitro grown chrysanthemum and rose after transfer to soil. A culture vessel is described which incorporates a selectively permeable membrane that permits diffusion of water vapour out of the culture vessel and thus reduces humidity. This vessel permitted entry of sufficient CO₂ to maintain photomixotrophic and photoautotrophic growth of roses under high irradiance in a greenhouse. Root development was enhanced by the high irradiance.