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Abstract
Most of plant growth regulators are known to alleviate negative effects of osmotic stress on crop growth. To evaluate the effects of cycocel (CCC), as a growth regulator, on crop seed germination, early growth, and vegetative growth under osmotic stress conditions, a study was conducted under controlled conditions. Six crops, wheat, barley, maize, sunflower, safflower, and rapeseed were grown under five osmotic potentials (0, as non-stress, −0.5, −1.0, −1.5, and −2.0 MPa), which were raised from seeds treated with three CCC concentrations (0, 2.5, and 3.5 g l−1). Reduced germination, seedling and vegetative growth as well as enhanced leaf free proline and chlorophyll content index were observed under osmotic stress. The extent of these changes depended on the type of the used crops. Priming with optimum CCC concentration mitigated to great extent stress-induced adverse effects on these crops. The positive effect of CCC priming on wheat, maize, and rapeseed was observed only at moderate osmotic levels, whereas on barley and safflower the priming effects were found in all levels of osmotic stress. However, sunflower did not respond to CCC priming treatments which might have been due to its thick achene coat. CCC priming was found to be effective in diverting a major proportion of assimilates to root, because root to shoot dry weight ratio increased due to CCC application under all osmotic stress regimes. Since barley and safflower were found to be most responsive to CCC priming, further research for better understanding of mechanisms of CCC priming on their germination and vegetative growth is recommended.