Department of Soils, Haryana Agricultural University, Hissar
Investigations carried out to find out the role of naphthalene acetic acid in the phenomena of abscisic acid promoted abscission in lower buds and bolls of cotton (Gossypium hirsutum L.) have shown the endogenous auxin (indole type) content to be high in retained bolls as compared to that in the abscising ones of the same age. Naphthalene acetic acid applied either to the intact buds or bolls or boll explants or sprayed in the field reduced shedding. The data did indicate “two stage” auxin response but it did not support the “Auxin gradient” concept. Naphthalene acetic acid applied alongwith the abscission promoter abscisic acid, could not only erase completely the promotive effect of abscission but also reduced the shedding over control. The data suggest that endogenous auxin content may be playing a key role in the phenomena of abscission in cotton buds and bolls and higher endogenous auxin content above a specific threshold seems to be controlling abscission of cotton bolls.
