Nitrate reductase activity in ‘Syrah’ grapevine under three irrigation strategies

The objective of this study was to evaluate the activity of the enzyme nitrate reductase in ‘Syrah’ grapevine under three irrigation strategies. Irrigation was applied by a drip system, and the treatments were started 45 days after production pruning. The statistical design was completely randomized in a 3 x 5 factorial, corresponding to three irrigation strategies: controlled deficit irrigation, deficit irrigation and full irrigation, and five collections along the cycle: at 54, 60, 73, 87 and 101 days after pruning. Deficit irrigation and controlled deficit irrigation treatments caused longer water deficit to plants and reduced nitrate reductase activity. Full irrigation treatment promoted the highest values of leaf water potential and nitrate reductase activity at the end of the cycle. Leaf water potential and leaf age influence nitrate reductase activity.