STUDIES ON INDUCTION OF AXILLARY FLOWERING IN MANGIFERA INDICA L.

Mango normally flowers from terminal buds. Axillary flowers may, however, appear if the apex of a shoot is damaged or removed, thus eliminating apical dominance. Reece et al (1, 2) experimentally induced floral initiation in axillary buds of Haden mango by decapitation of shoots in the presence of leaves. Under complete defoliation, decapitation had no flower inducing effect, indicating an essential role of leaves in floral induction. Singh and Singh (3) carrying out similar experiments with alternate and regular bearing varieties of mango confirmed the above results and noted a varietal difference in the response to the treatments. The regular bearing varieties showed more axillary flowering than the alternate bearing ones. The experiments reported herein were undertaken with the view to elucidating the physiological role of leaves on flowering in mango.

The experiments were conducted at Midnapore, West Bengal in two successive years, 1967–68 and 1968–69. In the first year only an intensively alternate bearing variety, Langra, was employed, while the second year a moderately regular bearing variety, Gulabkhas, was included. Three comparable trees in full bearing age (14-years-old) were selected in each variety. The Langra trees were in their 'off' year in the first year and in their 'on' year in the second year. The treatments were given at three different times (mid-October, mid-November and mid-December) representing the pre-, early and late fruit-bud differentiation stages. In the first year on each Langra tree twenty current year's shoots of comparable growth, distributed all over the three were selected at random at each time, while in the second year the total number of current year's shoots selected per tree per variety was fourty. All the selected shoots were decapitated by removing the apical bud together with the adjacent whorl of axillary buds with a sharp cut. Half the number of shoots per tree, selected at random, was immediately ringed on previous year's wood, approximately 7.5 cm below the base of current year's growth. The shoots on each tree, under ringing and no ringing, were then divided into five groups. In one group all the leaves of the shoots were allowed to remain as such, while in the remaining four groups the shoots were completely defoliated at intervals of 0, 4, 8 and 16 days after decapitation. Defoliation was done on the portion of the shoot up to the point of ringing in case of the ringed ones, and up to a comparable length from apex in case of the non-ringed ones. Effects of the treatments on axillary flowering on the shoots were noted in the following spring, in January-February.