Abstract: Plants are important medium for human to ingest selenium (Se) from external environment. Coffee (Coffea arabica) has strong ability to accumulate Se. To provide a technical reference for assessment of coffee growth and safe application of Se fertilizer during the production of Se-enriched functional coffee, a field experiment was carried out in Lujiangba, Baoshan City, Yunnan Province. The coffee cultivar ‘Typica’ was used as test material, with Se(IV)-rich nutrient solution containing 0-160 mg·L^-1 Se(IV) being sprayed on leaves during the filling stage of coffee. Photosynthetic characteristics, accumulation of selenium, iron and zinc of micro-elements in coffee, and the relationships among them were examined. The results showed that foliar application of 40-120 mg·L^-1 Se(IV) significantly increased plant height (17.6%-23.2%), the contents of chlorophyll a and chlorophyll b (12.6%-42.9% and 23.7%-45.8%), net photosynthetic rate (11.1%-36.7%), stomatal conductance (12.6%-22.9%), and the contents of total Se (19.8-67.8 and 3.1-30.4 times) in coffee leaves and green beans, respectively. Se-enriched green beans contained higher concentrations of total free amino acid (an increase of 12.5%-40.9%), soluble sugar (14.6%-36.5%), soluble protein (16.7%-44.3%), and several minerals, including copper (11.2%-29.9%), zinc (18.5%-70.5%), cobalt (12.8%-66.9%), iron (11.1%-19.2%), and magnesium (15.5%-45.9%). Those indices with higher contents occurred in Se-enriched leaves. However, foliar application of 160 mg·L^-1 Se(IV) inhibited those variables. Therefore, the proper concentration of a Se(IV)-rich nutrient solution (80-120 mg·L^-1 Se(IV)) can significantly increase net photosynthetic rate, contents of free amino acid, soluble sugar, soluble protein, total Se, and mineral elements in coffee leaves and green beans. This agronomic practice could be a promising strategy for production of Se-enriched functional coffee products and for the improvement of nutritional quality in coffee grown in Se-deficient soils.

Key words: coffee, foliar-spraying selenium(IV), selenium content, mineral element, photosynthetic characteristics, soluble sugar