Department of Plant Sciences

We subjected bean plants (Phaseolus vulgaris L. ‘Bianco di Bagnasco’) to phosphate deprivation stress and studied the enzymatic activity of some major anti-oxidative enzymes in both leaves and roots extracts. P deprivation provoked a significant decrease of catalase activity in leaves of 14-day-old plants, but no differences were measured after prolonged P deprivation. The enzyme activity in roots was not affected by the withdrawal of P from the culture medium. The deprivation of P from the growing medium provoked an increase in ascorbate peroxidase activity in leaves after 4 days of growth. No differences were detected in roots of +P and –P plants. Glutathione reductase activity decreased in leaves of 14 day-old P-deprived plants in comparison to +P plants. However, after 18 days of growth, the enzymatic activity was similar in both –P and +P plants. The deprivation of P provoked a significant decrease of glutathione reductase activity in roots of both 14 day-old and 18 day-old plants. The activity of dehydroascorbate reductase was increased in both leaves and roots, either after 4 and 8 days, by P withdrawal. The reduced availability of Pi in the plant tissues affected the activity of anti-oxidative enzymes mainly after the first days of deprivation, particularly in leaves. It could be suggested that during this period the plant is adjusting its metabolism to cope with the nutritional stress and that P-deprivation is acting as a mild oxidative stress.