ROLE OF GROWTH-REGULATORS IN IN-VITRO RHIZOME GROWTH OF POTATO

Disinfested, etiolated medial segments of potato (Solanum tuberosum L, ) sprouts cv. Katahdin with two axillary buds were placed on Murashige and Skoog (MS) medium in clear plastic culture boxes, Basal ends of e xplants were inserted into MS medium containing BA at 2 mg . liter(-1) . Nine treatments, composed of factorial combinations of GA, at 0, 0.2 , and 2 mg . liter(-1) and IAA at 0, 0.3, and 3 mg . liter(-1), were i mposed, These were applied via small agar cylinders placed on the apic al cut surface of each segment. Regardless of the presence of cytokini n and auxin, no rhizomes developed after 3 weeks in culture without a supply of GA(3), Number and length of primary and secondary rhizomes i ncreased with an increase in GA(3) concentration in the agar cylinder from 0 to 2 mg . liter(-1). Rhizome initiation and development appear to be controlled by coordinated participation of endogenous plant horm ones during the early events leading to tuber development. Chemical na mes used: oxy-1-methyl-8-methylenegibb-3-ene-1,10-carboxylic acid 1->4 lactone (GA(3)); indole-3-acetic acid (IAA); N-(phenylmethyl)-1H-puri n-6-amine (BA).