EFFECTS OF TYPE OF CARBOHYDRATE DURING PROLIFERATION AND ROOTING OF MICROCUTTINGS OF MALUS JORK-9

The type of carbohydrate used in the medium influenced the proliferation of Malus Jork 9. The microcuttings obtained showed marked differences in rooting ability. During proliferation, sorbitol (0.176 M) gave the best results. The plants grown on fructose (either directly added or resulting from the hydrolysis of sucrose) showed a definite tendency to become an unorganised structure. This abnormal growth showed similarities with the ''cancerisation'' of microcuttings in the presence of very high cytokinin levels ! This BAP toxicity could be caused by a higher contact surface due to softer gel, this in turn being caused by lowering of pH after autoclaving. During rooting, it seems that both the sugar used during proliferation and that present in the rooting medium influenced the criteria chosen. The best results were obtained with sucrose (0.088 M) during proliferation and glucose (0.088 M) during rooting. Statistically, however, they did not differ from sorbitol (0.176 M) used during both phases of culture.