LATERAL BUD GROWTH INMANGIFERA INDICA L. IN RELATION TO AUXIN AND INHIBITOR CONTENT OF SHOOTS AND FRUITS

The inhibition of lateral buds by the shoot apex i.e., apical dominance, is a phenomenon widespread throughout the plant kingdom and the degree of inhibition varies greatly among the species. The involvement of auxin in this penomenon has been shown in many cases (12, 13, 22, 23, 24, 25). However, doubts have been expressed from time to time regarding the role of auxin in the inhibition of lateral buds and quantitative uncertainties have been reported (1, 2, 3).

More than 30 years ago, Snow (21) postulated that the correlative inhibition of lateral buds in pea seedlings involves not only auxins, but also growth inhibitors. The involvement of inhibitors in various growth processes has been confirmed (7, 8, 9, 10, 11, 14, 15, 16, 17, 18, 19). Dorffling (5, 6) has recently shown for seedlings of Acerpseudoplatanus that decapitation and defoliation result in a marked reduction of inhibitor level in the lateral buds, which is followed by the outgrowth of buds. Application of the inhibitor to decapitated and defoliated seedlings of this species and to decapitated plants of pea results in the inhibition of lateral buds. These observations of Dorffling have been confirmed by Wareing (26) for Acerpseudoplatanus and Ribesnigrum.

Now these various experimental observations are highly interesting and may well prove to be significant for an understanding of the mechanism of correlative inhibition of buds. The observed correlation between the fall in inhibitor level and outgrowth of lateral buds following decapitation is of great interest and the increasing evidence for the role of inhibitors in dormancy renders their role in correlative inhibition more plausible, since Champagnat (4) has argued that correlative inhibition and bud dormancy are related phenomena. In the experiments described here an attempt has been made to study the lateral bud growth in mango in relation to auxin and inhibitor content of shoots and fruits.

Experiments were conducted at the orchards of the Division of Horticulture, Indian Agricultural Research Institute, New Delhi. Fourteen year old healthy uniform mango trees of variety Dashehari were selected for these studies. Two trees, when in full bloom, were completely deblossomed in the month of March for the collection of comparable samples and three trees in full bearing condition were selected for conducting the field experiments.

The following field experiments were conducted to determine the possible involvement of natural inhibitors in the apical dominance.