Studies on the control of flowering and fruiting of pineapples by the application of plant hormones and allied compounds

Abstract

While in the vast majority of the plants synthetic auxins in their physiological concentrations cause inhibition or delayed flowering, their effect in pineapple and litchi is found to be sharply different in that the flowering of these plants is very much augmented after appli-cation with them. This has caused a growing interest in the field of flowering of plants in general and that of pineapple plant in particular. The other partinent question lies in auxin-synthesis mechanism existing in the stem apex and leaf bases of this plant (Gordon and Nieva, 1949 ; van overbeek, 1946); from auxin precursors Indole acetaldehyde, to indoleacetic acid (IAA), the only native auxin of plants so far discovered. The logical conclusion is that the flow-ering of pineapple is an auxin controlled process. This conclusion, however, appears to suffer from inconsistancy owing to the fact that acetylene and ethylene, two unsatura-ted hydrocarbons also exert an identical influence on induc-tion of early flowering in this plant (Rodriguez, 1932). These contrasting reports make the problem much more fascinating. With the main object of elucidating the mechanism of auxin action in the flowering and fruit formation of this plant, the present investigation was undertaken. The other associa-ted problem lies in examining the quality of fruits likely to be improved after treatment with auxins. Pineapple plants of variety Giant Kew as selec-ted for the purpose, since in the preliminary trial experi-ments conducted in the experimental farm of Agricultural Botany, this variety proved superior over the other varie-ties in its response to auxin application. Auxin NAA was first applied to the stem apex and leaf bases in aqueous sol-ution using two sets of concentration ranges, in the first set relatively dilute concentrations from 50 to 200 ppm. were used, and in the second set higher concentrations from 250 to 1,000 ppm. were employed for clear appraisal of the optimal and inhibitory level of concentrations. The results revealed that optimal level...