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Abstract
HORMONAL RELATIONS IN THE DEVELOPMENT OF ORCHID OVARY. II. — The effects of auxins on isolated parts of the flower axis. — The changes in fresh weight of segments of column, ovary and peduncle of Cymb[icaron]dium sp., treated in vitro with auxins (IAA, EtIA and NAA) indicate that these parts of the flower react promptly and independently to the three auxins tested. Expansion is very small in the ovary, and is more and more large moving towards the apex of the flower (fig. 1). The apical part of the column reacts somewhat more rapidly to auxin and tolerates higher concentration than the proximal part.
Naphtalenacetic acid proved to be the most active of the three auxins tested. This finding is in agreement with the higher efficiency of this substances as an inducer of parthe-nocarpy and its ability to induce large necroses of the column, when applied to the flower on the intact plant.
The plots of auxin activity against concentration of the auxins suggest thai the lower activity of IAA might be due to its destruction by indoleacetic acid oxidase.