CALLUSING FROM RICE ROOT EXPLANTS - ADVENTITIOUS ROOT-FORMATION PRECEDES CALLUS INITIATION RESPONSE

The phenomenon of adventitious root induction from various parts of th e plant system under specific experimental conditions is widely practi sed. We note in this study that roots excised from 7-day-old rice seed lings when cultured on Murashige and Skoog's nutrient medium supplemen ted with a,4-dichlorophenoxyacetic acid produced a large number of adv entitious roots. It was further noted that the basal cells of the adve ntitious roots dedifferentiate to form calli masses. This response of adventitious root formation and callusing was 100% as all the tested r oot explants formed adventitious roots. Apart from four different cult ivars of rice, three other genera namely wheat, maize and brassica sho wed formation of adventitious roots and calli under culture conditions . The monocot genera (rice, wheat and maize) showed more conspicuous r ooting and callusing response as against brassica (a dicot). Adventiti ous root-derived rice calli were shown to regenerate shoot primordia w ith high frequency (88%) upon transfer to the same medium devoid of 2, 4-dichlorophenoxyacetic acid.