The major portion of IAA-2-14C, applied to stigmas of whole flowers of Angraecum cv. Veitchii and Cattleya cv. Porcia Cannizaro, as well as to excised gynostemia of the latter, was immobilized at the point of application. A limited amount of nonpolar transport occurred. Some of the auxin was conjugated into IAA-aspartate in a process which is inhibited by cycloheximide, suggesting a requirement for de novo protein synthesis. Because the effects of pollination and auxin application spread quickly to floral segments, additional substances, from pollen or produced by pollinated flowers, may participate in the regulation of postpollination phenomena in orchid flowers.

Pollination or treatment with naphthaleneacetic acid, 50 .mu.g per flower, prevented the death of gynostemia on blossoms of Cattleya Porcia ’Cannizaro’. Auxin treatments, as well as emasculation and pollination, increased anthocyanin levels. After applications of indoleacetic acid (IAA)-2-14C, stigmatic extracts contained IAA, IAA-aspartate and other degradation products. Cycloheximide and actinomycin D reduced the formation of IAA-aspartate. Some of the postpollination phenomena exhibited by Cattleya Porcia ’Cannizaro’ are similar to those of other orchids. Light and electron microscopic studies showed that removal of the pollinia damages the outer cells of the rostellum of Phalaenopsis flowers. Cells in some regions of the ground tissue of the rostellum close to a vascular bundle contain relatively large numbers of mitochondria. These observations suggest that the rostellum is well adapted for ethylene production. The initial evolution of ethylene may result from wounding, which, in turn, probably causes increased production of the hormone.