Macronutrient deficiencies in stevia: visual symptoms and effects on growth, chemical composition, and stevioside production

Abstract

This experiment was carried out to describe visual symptoms of macronutrients deficiencies in Stevia rebaudiana, and the effects of these deficiencies on growth, chemical composition and stevioside production. The symptoms were: yellowing with -N; dark green leaves with -P; clorotic, mottled, and necrotic leaves, with -K; apical necrosis, with -Ca; leaves with clorosis and necrosis in inverted "V" shape, with -Mg, and small pale green leaves, with -S. N, K, and Mg deficiencies reduced the leaf growth, therefore the plant marketable part. Mg deficiency caused greater reduction on the development of the radicular system. N, P, K, and S deficiencies decreasead the shoot:root dry weigth ratio, while Mg deficiency increased it. All deficiencies decreased the absorption of macronutrients, except of Ca, which reduced only the absorption of Ca, and K, that did not affect the absorption of Mg and S. The chemical content of the last five fully expanded leaf pairs showed good correlation with the plant nutritional status. The deficiencies of K, Ca, and S decreased the concentration of stevioside while all deficiencies, except of P, decreased the stevioside content.