Carbonic Anhydrase Activity in Plants in Relation to Zinc Content

Abstract

Throughout the life cycle of oat plants carbonic anhydrase activity, which is restricted to the non-chloroplast fraction of leaves, reaches a maximum value and then decreases. After appearance of deficiency symptoms, carbonic anhydrase activity is less in Zn-deficient plants than in full manured control of the same age and is associated with lower Zn content of the leaves. An expt. is described wherein uniform tomato plants were grown in Zn-deficient water cultures. With the onset of Zn deficiency symptoms, which are described, 4 concns. of Zn were added to solns. in which the plants were growing; in order to minimize growth changes plants were harvested at short time intervals after appln. and carbonic anhydrase activity and Zn and protein-N contents were measured at each harvest. Carbonic anhydrase activity showed highly significant positive linear correlation with both Zn and protein-N contents. Evidence is presented which indicates that in Zn-deficient plants carbonic anhydrase activity is less than in normal plants through blocking of metabolic reactions leading to formation of protein and not by absence of sufficient Zn to activate an apoenzyme.