Carbonic Anhydrase Activity in Leaves of Wheat Genotypes Differing in Zn Efficiency

Activity of carbonic anhydrase (CA) (EC 4.2.1.1) was determined in leaf extracts of two wheat genotypes (Triticum aestivum L., cv. Warigal, and T. turgidum L. conv. durum (Desf.) MacKey, cv. Durati) differing in Zn efficiency. Generally, CA activity decreased with plant age in both genotypes. Under sufficient Zn supply, the two genotypes had the same CA activity; under Zn deficiency, however, a 2-fold higher CA activity was recorded for Zn-efficient Warigal than for Zn-inefficient Durati. When Zn-sufficient plants were transferred into solutions with low Zn supply, plants of the cv. Durati lost a greater portion of CA activity than those of the cv. Warigal. Upon re-supply of Zn to the Zn-deficient plants, Durati lost an ability to increase CA activity, while Warigal showed a saturating, curvilinear increase in CA activity under the same conditions. For any given Zn concentration in leaf tissue, Zn-efficient Warigal showed greater CA activity than Zn-inefficient Durati. An ability of Zn-efficient wheat genotypes to maintain greater CA activity under Zn deficiency may be beneficial in maintaining the photosynthetic rate and dry matter production at a higher level, a characteristic that may be especially important for wheat as a species with inherently lower CA activity compared to other species.