For evaluation of growth parameters of strawberry callus under osmotic stress and exogenous proline, embryonic calli were transferred to Murashige and Skoog (MS) medium containing four sucrose (osmotic stress) treatments including 3, 6, 9 and 12% and various concentrations of exogenous Lproline (0, 2.5, 5 and 10 mM) supplemented with 1 mg/l of 2,4-dichlorophenoxyacetic acid (2,4-D) + 0.5 mg/l 6-benzyl amino purine (BAP). After four weeks, various morpho-biochemical parameters of calli were studied. Callus fresh and dry weight was strictly dependent on the concentration of sucrose in the medium. When the concentration of sucrose in the medium was increased from 3 to 9%, the amount of fresh weight was decreased, while dry weights increased in callus tissues. High concentration of sucrose (12%) caused the least content of fresh and dry weight in calli. When the concentration of sucrose in the medium was increased from 3 to 12%, the amount of free proline of callus was increased. Addition of exogenous proline to the culture medium improved the growth of calluses and intracellular free proline. The highest content of fresh weight (601.09 mg), dry weight (134.68 mg) and content of proline accumulation (11.12 Moles/g fresh weight) were obtained in calli grown on media containing 10 mM proline, while the least content of fresh weight (297.62 mg), dry weight (49.55 mg) and free proline accumulation (0.817 Moles/g fresh weight) were observed in calli of control (without proline).
