PHYSIOLOGICAL AND BIOCHEMICAL CHANGES ACCOMPANYING POLLINATION IN ORCHID FLOWERS: I. GENERAL OBSERVATIONS AND WATER RELATIONS

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Abstract
Pollination of orchid flowers and treatments with indoleacetic acid and naphthaleneacetic acid cause increases in both fresh and dry wts. of the column. The greater % increase of fresh wt. over dry wt., followed by a reversion of this relationship, indicates an initial dominance of water uptake over the increase in dry matter. The perianth after treatment loses water and dry-matter also. A slight increase in osmotic pressure is found 115 hrs. after treatment but it is not sufficient to account for the changes observed in water uptake. Cut discs of columns of treated flowers take up more water on a % basis than those from untreated flowers. The difference in water uptake is established within 30 min. and is not found in a N2 atmosphere. Columns from treated flowers have a greater water holding capacity. The wilting of the perianth after treatment results from an increased rate of epidermal transpiration.