Osmotic Adjustment and Growth of Salt-stressed Cotton as Improved by a Bioregulator

For examining links between growth of salinity-exposed cotton and corresponding changes in physiological characters, a bioregulator was used as a tool for specific manipulations. Greenhouse-grown cotton ( Gossy-pium birsutum L. cv. Paymaster 145 ) was subjected to NaCl levels up to 14.9 dS m⁻¹. The bioregulator MCBuTTB, a cytokinin analog with known ability in improving growth and yield in several salt-stressed crops, was applied by imbiding seed (0 or 268 ppm) plus one foliar spray in dosages equaling 0, 1, and 3 kg ha⁻¹ at 45 DAP. MCBuTTB improved germination, growth, flowering, and finally boll weight. This result coincided with lower osmotic and higher water potentials in leaves, higher leaf turgidity, and more agilely reacting stomata. Treated plants had higher K and preferably Na concentrations in its leaves but ion accumulation was not a precondition for osmotic adjustments, because in cotton exposed to a manmtol-simulated drought MCBuTTB triggered a similar osmotic adjustment and sustained vigour. Regression analyses indicated that osmotic adjustment alone did not cause the raised leaf turgidity. All characters which contribute to salinity resistance appeared as mutually depending and interacting but they respond to a regulatory agent of cytokinin-like activity.