Effects of sugars, gibberellic acid and kinetin on acid invertase of developing carrot roots

Abstract

The activities of acid invertase carrot roots 32, 50 and 60 days old were, respectively, 5.7, 1.4 and 0.5 nkat/g fr. wt. When portions of such roots were excised and incubated in water for 20 hr the activities of the enzyme rose, respectively, to 9.7, 14.4 and 18.4. Fructose (50 mM), GA (30 μM) and kinetin (50 μM) affected the rise in invertase activity, GA stimulating it and fructose and kinetin decreasing it. The magnitude of these effects varied, however, with the age of the roots. Fructose had the highest effect in young non-tuberized roots while the effects of kinetin and GA were highest in mature tuberous roots. A 48 hr incubation of discs from mature roots in fructose plus kinetin reduced the rise in invertase activity by 75%; nevertheless, fructose plus kinetin could not abolish, even after 66 hr of incubation, the ca 10% increase in invertase activity produced by a 1 hr GA pulse treatment applied at 0 hr.