Effects of gibberellins on abscission in cotton seedling explants |
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Authors: | J. L. Lyon O. E. Smith |
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Affiliation: | (1) Department of Agronomy, University of California, Davis;(2) Crops Research Division Agricultural Research Service, U. S. Department of Agriculture University of California, Davis, California, U.S.A. |
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Abstract: | Summary Gibberellic acid (GA3) accelerated abscission when applied, in a wide concentration range, to excised abscission zones of cotton. Abscission was promoted equally by distal or proximal applications of from 10-3 to 100 g. A slight, but inconsistent, abscission retardation was obtained with distal applications of 10-6 and 10-7 g.Seven different gibberellins accelerated abscission equally when applied distally at amounts of 5×10-4 to 5×10-1 g per abscission zone. At 5×10-5 g there were great differences in effectiveness; their activities can be ranked: A3>A5A4>A7=A8>A1=A9.The ready translocatability of GA3 was suggested when 1.0 or 0.01 g was applied to one petiole, and the opposite untreated petiole abscised at the same time as the treated one. However, 0.001 g was not effective in moving across the stem and inducing abscission of the untreated petiole.The rate of abscission of petioles treated with 1.0 g GA3 was not affected by increasing the length of the petiole from 3 to 9 mm. However, abscission of petioles treated with smaller amounts is inversely proportional to petiole length.The rate of abscission of petioles treated with GA3 decreased with increasing seedling age; there was a simultaneous increase in abscission rate of the controls.Part of this research was based on a portion of a thesis submitted by the senior author to the Graduate Division, University of California, Davis, in partial fulfillment of the requirements for the M.S. degree. |
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