Nitrate Reductase Activity in Calcifugous and Calcicolous Tomatoes as Affected by Iron Stress

Abstract

AbstractCalcicolous plants are generally more Fe‐efficient than calcifugous plants, because they respond to Fe stress by releasing H‐ions and “reductants” from their roots that causes Fe to become available. The objective of our study was to determine if differential response to Fe stress in calcicolous and calcifugous varieties affects nitrate reductase activity. T3238FER (Fe‐efficient) and T3238fer (Fe‐inefficient) tomato (Lycopersicon esculentum Mill.) cultivars were grown in nutrient solutions supplied with N as NH4+‐N plus NO3−‐N, and as NO3−‐N only. The chemical reactions induced by Fe stress concomitantly increased nitrate reductase activity in roots and tops of calcicolous, but not in calcifugous tomato. This nitrate reductase activity decreased, however, when Fe was made available to the plants. When Fe stress was eliminated by adding Fe, nitrate reductase activity was comparable in the two cultivars.