SE-ENRICHMENT OF CARROT AND ONION VIA FOLIAR APPLICATION

The aim of this work was to study the selenium accumulation in carrot and onion plants using foliar application by sodium selenite and sodium selenate. Furthermore, we aimed at identifying the Se species biosynthesised by onion and carrot plants. The results were used to prepare for production of 77Se enriched plants for an ongoing human absorption study

Effect of foliar application of selenium on its uptake and speciation in carrot

Carrot (Daucus carota) shoots were enriched by selenium using foliar application. Solutions of sodium selenite or sodium selenate at 10 and 100 lg Se ml�1, were sprayed on the carrot leaves and the selenium content and uptake rate of selenium were estimated by ICP–MS analysis. Anion and cation exchange HPLC were tailored to and applied for the separation of selenium species in proteolytic extracts of the biological tissues using detection by ICP–MS or ESI–MS/MS. Foliar application of solutions of selenite or selenate at 100 lg Se ml�1 resulted in a selenium concentration of up to 2 lg Se g�1 (dry mass) in the carrot root whereas the selenium concentration in the controls was below the limit of detection at 0.045 lg Se g�1 (dry mass). Selenate-enriched carrot leaves accumulated as much as 80 lg Se g�1 (dry mass), while the selenite-enriched leaves contained approximately 50 lg Se g�1 (dry mass). The speciation analyses showed that inorganic selenium was present in both roots and leaves. The predominant metabolised organic forms of selenium in the roots were selenomethionine and c-glutamyl-selenomethyl- selenocysteine, regardless of which of the inorganic species were used for foliar application. Only selenomethionine was detected in the carrot leaves. The identity of selenomethionine contained in carrot roots and leaves was successfully confirmed by HPLC–ESI–MS/MS

Effect of foliar application of selenium on its uptake and speciation in carrot

Carrot (Daucus carota) shoots were enriched by selenium using foliar application. Solutions of sodium selenite or sodium selenate at 10 and 100 lg Se ml�1, were sprayed on the carrot leaves and the selenium content and uptake rate of selenium were estimated by ICP–MS analysis. Anion and cation exchange HPLC were tailored to and applied for the separation of selenium species in proteolytic extracts of the biological tissues using detection by ICP–MS or ESI–MS/MS. Foliar application of solutions of selenite or selenate at 100 lg Se ml�1 resulted in a selenium concentration of up to 2 lg Se g�1 (dry mass) in the carrot root whereas the selenium concentration in the controls was below the limit of detection at 0.045 lg Se g�1 (dry mass). Selenate-enriched carrot leaves accumulated as much as 80 lg Se g�1 (dry mass), while the selenite-enriched leaves contained approximately 50 lg Se g�1 (dry mass). The speciation analyses showed that inorganic selenium was present in both roots and leaves. The predominant metabolised organic forms of selenium in the roots were selenomethionine and c-glutamyl-selenomethyl- selenocysteine, regardless of which of the inorganic species were used for foliar application. Only selenomethionine was detected in the carrot leaves. The identity of selenomethionine contained in carrot roots and leaves was successfully confirmed by HPLC–ESI–MS/MS