Effect of Zinc Deficiency on Alcohol Dehydrogenase Activity and Nutrient Uptake in Rice

Abstract

AbstractZinc deficiency in rice (Oryza sativa) usually occurs after flooding. A greenhouse experiment was conducted to determine if the metabolic disorders associated with Zn deficiency in flooded rice are due to decreases in alcohol dehydrogenase (ADH) or glutamate dehydrogenase (GDH) activities, or both, in the roots, since Zn is a cofactor in these enzymes. ‘Saturn’ rice, a variety characterized as being susceptible to Zn deficiency, was grown in 20 pots containing 3 kg of Crowley silt loam soil (fine, montmorillonitic, thermic Typic Albaqualf). Half of the pots received 1 mg Zn/kg as ZnEDTA; the other half served as controls. Five days after flooding the control plants showed signs of Zn deficiency. The plants were harvested 17 d after flooding. Aboveground dry matter production by the fertilized plants (x̄=0.91 g) was significantly greater than that of the Zn‐deficient control plants (x̄=0.24 g). Plant tissue analysis revealed that Zn‐deficient plants accumulated divalent cations at the expense of monovalent cations, possibly indicating the increased production of a divalent charge‐specific carrier. Root GDH activities of the control and fertilized plants were not significantly different. However, ADH activities in the roots of plants that had received Zn were more than twice as high as those in control plants. Root ADH activity was also correlated with Zn concentration in the leaves (r=0.78**). It is hypothesized that decreases in the ADH activity of Zn‐deficient flooded rice result in less ATP production, thereby reducing vital metabolic activities of the roots.