Effect of arginine and urea on polyamines content and growth of bean under salinity stress

Prior to sowing, seeds of bean (Phaseolus vulgaris L.) were treated with 4 mM arginine or 0.1% urea, as nitrogen source. The seeds were then subjected to salinity stress. Arginine and urea treatments stimulated germination of both unstressed and salinity-stressed seeds. It was interesting to observe that the increased germination percentage in response to arginine and urea treatments was associated with increased content of polyamines, particularly putrescine (Put), spermidine (Spd) and spermine (Spm). Growth of the seedlings was also improved by application of arginine and urea, which was also associated with increased content of the polyamines Spd and Spm, while the Put content decreased. Total soluble sugars were much accumulated in response to arginine and urea treatments under salinity stress for cellular osmoregulation. The ratio of K+/Na+ increased in the leaves by application of arginine and urea, indicating a more alleviation to the adverse effects of salinity stress. Changes in proteinogenic amino acids were also investigated.