Evaluation of hydrogen ion secretion relative to zeatin induced growth of detached cucumber cucumis sativus cultivar marketer cotyledons

Ross, C.W.; Rayle, D.L.

Plant Physiology (Rockville) 70(5): 1470-1474


ISSN/ISBN: 0032-0889
Accession: 005398867

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Cytokinins promote expansion of cotyledons detached from seedlings of more than a dozen species. The zeatin-enhanced expansion of cucumber (C. sativus L. cv. Marketer) cotyledons was investigated. Whether acid secretion is involved in wall loosening accompanying such accelerated growth was evaluated. For cotyledons abraded with carborundum or cut into either 8 or 18 pieces, no zeatin-enhanced acidification of the growth medium during growth periods of 3 days was detected. Measurements of ph values on each surface of zeatin-treated, abraded cotyledons after 3 days of growth also showed no detectable acidification caused by the hormone. With several buffers at pH values ranging from 5 to 8, growth of nonabraded, abraded or cut cotyledons with or without zeatin was independent of external ph. Experiments restricted to .apprx. 12 h indicated that certain acidic buffers enhanced growth of cotyledons cut into 18 pieces. Concentrations of fusicoccin that caused growth promotion equal to that of zeatin initiated substantial acidification of the medium. Apparently, zeatin-induced expansion of detached cucumber cotyledons is independent of H+ secretion.