Date of Award
Program or Major
Doctor of Philosophy
Apical applications of 0.2 micrograms N('6)-benzyladenine (BA), a synthetic cytokinin, or 5 micrograms gibberellic acid (GA) significantly enhanced hypocotyl elongation in intact dwarf watermelon seedlings. Accompanying the increase in hypocotyl length was increased expansion of the cotyledons and inhibition of root growth. A study on dry matter partitioning indicated that both hormones caused a preferential mobilization of metabolites from the cotyledons to the hypocotyl at an expense to roots. However, in comparison to untreated or GA-treated seedlings, BA decreased total translocation of metabolites out of the cotyledons. Hormonal effects on water potential of cotyledons and hypocotyls were determined by allowing organs to equilibrate for 2 h in serial concentrations of polyethylene glycol 4000. Osmotic potentials were determined with a dewpoint microvoltmeter. Results of a time-course study of hormonal effects on water and osmotic potentials indicated that BA stimulated cotyledon expansion and hypocotyl elongation primarily by increasing cell wall extensibility, whereas GA-promotion of cotyledon expansion and hypocotyl growth involved osmoregulation in addition to a lowering of the yielding threshold of the cell wall. Measurements of soluble sugars by a colorimetric procedure and cations by atomic absorption spectrometry confirmed that GA promoted the accumulation of osmotically active solutes in the cotyledons and hypocotyls.
ZACK, CHERYL DIANE, "COMPARATIVE EFFECTS OF GIBBERELLIC ACID AND N(6)-BENZYLADENINE ON GROWTH AND DEVELOPMENT OF DWARF WATERMELON SEEDLINGS" (1981). Doctoral Dissertations. 1315.