Effects of putrescine, ammonium nitrate and IAA in ameliorating metal and salinity induced stress in mustard seedlings

Change in IAA oxidase activity in the leaves of mustard seedlings grown in controlled condition under metal and salinity stress in presence of putrescine, ammonium nitrate or IAA were examined in order to understand the putrescine amelioration of growth retardation under stressful conditions. IAA oxidase activity in the leaves increased substantially under heavy metal and salinity stress. Supply of putrescine (1 mM), ammonium nitrate (10 mM) or IAA (10 μM) arrested the increase in IAA oxidase activity under stress. Putrescine induced retardation in enzyme activity was about 40% in leaf of the seedlings exposed to severe stress, either 2mM metal and/or 100 mM NaCl salinity. Putrescine caused increase in general protein level, about 2–3 fold over either control or ammonium nitrate or IAA. Reduetion in endogenous metal accumulation (by 50%) in leaf and increased seedling elongation and growth with putrescine was correlated with IAA oxidase activity. However, Ca⁺⁺ and Mg⁺⁺ level did not change much in leaf with any of the treatment. It seems that putrescine amelioration of growth in stressed seedling might be through modulating IAA oxidase activity and sparing IAA.