Effect of growth regulators on photosynthesis, transpiration and related parameters in water stressed cotton

Gas exchange in Gossypium hirsutum L. cv. H-777 as affected by water deficit and growth regulators (IAA, GA(3), BAP, ABA, ethrel) was examined. Sixty days after sowing, growth regulators in concentration 50 muM were applied as foliar spray and irrigation was withheld to get desired (moderate and severe) water deficit. All the parameters were measured on the third leaf from the top between 10:00 and 11:00. Net photosynthetic rate (P-N), transpiration rate (E), stomatal conductance (g(s)), carboxylation efficiency (CE), and water potential (psi (w)) decreased significantly with the increasing water stress, however, water use efficiency (WUE) was unaffected. Foliar spray with IAA, GA3 and BAP partially counteracted the effect of water deficit on the above parameters except psi (w), which became more negative. ABA and up to some extent ethrel increased WUE and maintained higher psi (w), however, caused further decrease in P-N, E, and g(s).