Effet du nitrate d’ammonium sur le développement et l’activité des enzymes anti-oxydantes du fraisier (Fragaria x ananassa L.) micropropagé

Effect of ammonium nitrate on the development and anti-oxydant enzymes activity of strawberry (Fragaria x ananassa L.) propagated in vitro. The addition of ammonium nitrate (NH4NO3) at different concentrations (500, 1000 and 1500 mg.l-1) to the in vitro multiplication medium improved significantly the vigor and reversed the leaf chlorosis affecting the strawberry shoots when cultivated on Boxus standard medium, which only contains nitrate as source of nitrogen. The analysis performed with both susceptible « Chandler » and more tolerant « Sweet Charlee » varieties showed that NH4NO3 would confer a more favorable and less stressful nutritional situation to the vitroshoots. Higher quantity of total soluble proteins and improvement of CAT and POD enzymatic activities in both varieties are the single changes observed in the metabolism of the shoots cultivated in presence of ammonium nitrate. This situation allowed those shoots to protect their membrane lipids against peroxydation due to a better activity of their anti-oxidant enzymes.