Present investigations were carried out to evaluate the comparative studies of effects of different plant growth regulators and salt stress on physiological and biochemical characters of Cotton (Gossypium hirsutum L.). The first experiment comprised initial screening of the 18 cultivars of cotton for salt tolerance at 2 growth stages i.e. germination and seedling stages and subsequently the four selected varieties were evaluated for their response to salt. Four concentrations of NaCl (7.5 dSm-1, 10dSm-l, 15 dSm-1 and 20 dSm-1) were applied. On the basis of average germination %age and fresh and dry weight of root and shoot, the cultivars were classified as tolerant, moderately tolerant, moderately sensitive and sensitive. Cultivars NIAB KARISHMA and CIM1100 were tolerant. Cultivars MNH448, CIM240 and MNH345 were sensitive varieties. Cultivars B-557, MNH156 and MNH440 were considered as moderately sensitive varieties. Cultivars CIM109, CIM243, CIM70, MNH93, MNH147, MNH440, MNH295, MNH321, MNH348, MNH356 and NIAB78 were classified as moderately tolerant varieties.
The second experiment comprised field study for three consecutive years with 4 cultivars differing in salt tolerance viz cv NIAB KARISHMA and CIMII00, the salt tolerant cultivars and cv MNH448 and CIM240 the salt sensitive cultivars. Field experiment involved evaluation of the effects of 5 growth regulators viz abscisic acid (ABA), benzyl adenine (BA), cycocel (CCC), indole acetic acid (IAA) and gibberrellic acid (GA3) used as seed soaking (10-5M), foliar spray (10-5M) and seed soaking + foliar spray on plant height, leaf area, number of bolls plant-1, size of boll, 1000-seeds weight, seed cotton yield, lint yield, seed protein contents, seed oil contents, fibre length, fibre fineness, fibre strength, fibre maturity and lint cellulose contents. The five growth regulators were evaluated for their response during the first year and three regulators viz abscisic acid (ABA), benzyl adenine (BA) and cycocel (CCC) were selected on the basis of their performance. Combined application of seed soaking + foliar spray proved better for all the above mentioned parameters except plant height, leaf area and number of bolls plant-1.
Third experiment comprised green house study of the effect of 2 selected salt concentrations (15 dSm-1 and 20 dSm-1) and 2 growth regulators viz abscisic acid (ABA) and cycocel (CCC) used as seed soaking (10-5M) and foliar spray (10-5M) used alone and in combination with salt, on all the parameters mentioned above. It is inferred that cultivars MNH448 and CIM240 showed greater % decrease in all the parameters mentioned above than cultivars NIAB KARISHMA and CIMII00 following 15 dSm-1 and 20 dSm-1 NaCl treatments. Both seed soaking as well as foliar spray of ABA and CCC ameliorated the inhibitory effect of salt and significantly increased all the parameters mentioned above except plant height which decreased significantly in all the cultivars. Both methods of application of ABA and CCC were equally effective.
Field experiment studies revealed that seed soaking + foliar spray of cycocel (CCC) showed promising effects than that of seed soaking + foliar spray of ABA and BA and increased seed cotton yield by 26% and 21 % in salt tolerant and salt sensitive cultivars respectively. Fibre length, fibre fineness and fibre strength were also maximum due to this treatment but the increase did not differ significantly among salt tolerant and salt sensitive cultivars.
In pots under semi controlled conditions in green house, CCC also followed the similar pattern of response and increase seed cotton yield fibre length, fibre fineness and fibre strength but promoting effect of CCC was not as that of field experiment.
Cycocel is far cheaper than ABA or BA and is regularly applied in agriculture and horticulture as it has great costlbenefit ratio. Hence CCC either applied as seed soaking (10-5M), foliar spray (10-5M) and seed sociking + foliar spray is recommended to ameliorate salt stress and to increase seed cotton yield, fibre quality, seed quality and lint cellulose contents in cotton.