Paclobutrazol induced changes in carbohydrates and some associated enzymes during floral initiation in mango (Mangifera indicaL.) cv. Totapuri

In order to study the role of carbohydrates in the paclobutrazol induced floral initiation in mango (Mangifera indicaL.), the carbohydrate contents and the activities of amylase and sucrose metabolizing enzymes were analyzed in the apical buds and leaves of growing shoots at 4 bud developmental stages numerically characterized as 510 (initiation of bud swelling), 511 (swollen buds), 513 (bud burst) and 515 (panicle emergence) according to standard BBCH scale. The soil drenching treatment of paclobutrazol @ 3.0 ml m−1canopy diameter to the mango cv. Totapuri resulted in increase in the contents of total soluble sugars, reducing sugars, starch, sucrose, glucose and fructose in the apical buds and leaves, and the increases were greater in apical buds. Both in the paclobutrazol treated and control trees, the contents of total soluble sugar, reducing sugar, sucrose, glucose and fructose showed a progressive increase from 510 to 513 bud developmental stages and declined subsequently. In contrast, leaf starch showed a consistent declining pattern from higher value at 510–515 bud developmental stages. The amylase activity in leaves declined, while the activities of acid invertase (AI), sucrose synthase (SS) and sucrose phosphate synthase (SPS) increased significantly in the apical buds of paclobutrazol treated trees as compared to control, with peak activity witnessed at 513 bud developmental stage. The results indicated that paclobutrazol induced flowering is accompanied by an increase in starch in leaf concomitant with an increase in soluble sugars like sucrose, glucose and fructose in apical buds and inhibition in the amylase activity in association with increase in the activities of AI, SPS and SS in the apical buds.