Response of carboxylate metabolism to Zn deficiency in Lactuca sativa and Brassica oleracea plants

Abstract

Different species or genotypes differ in their Zn use efficiency (ZnUE) under low Zn availability in the soil. Organic acids (OAs) synthetised by plant carboxylate metabolism could play a role in Zn-deficiency tolerance. The main objective of the present work was to assess the response of two species of great agronomic interest such as Lactuca sativa and Brassica oleracea to Zn deficiency focusing on OAs and carboxylate metabolism. For this, L. sativa and B. oleracea plants were grown in hydroponic culture with different Zn-application rates: 10 µM Zn as control and 0.1 µM Zn as deficiency treatment. ZnUE parameters, OAs concentration and carboxylate metabolism enzymes were analysed. L. sativa accumulated more Zn and registered better Zn uptake efficiency (ZnUpE) while B. oleracea lost less biomass and it registered better Zn utilization efficiency (ZnUtE). In L. sativa citrate and oxalate concentrations and PEPC and CS activities increased while FUM and MDH activities declined. In B. oleracea no significant response were found in OAs concentration neither carboxylate metabolism except for a decrease in FUM activity. These results suggest that a possible factor that induces TCA cycle could be a low ZnUtE rather than a low Zn concentration under Zn-deficiency conditions. In L. sativa citrate, oxalate, PEPC and CS could play a key role to face Zn deficiency while in B. oleracea the higher ZnUtE can not be explained by a rise in OAs synthesis.