Macronutrient deficiencies in Stevia: Visual symptoms and effects on growth, chemical composition, and stevioside production

This experiment was carried out to describe visual symptoms of macronutrien ts deficiencies in Stevia rebaudiana, and the effects of these deficiencies on growth, chemical composition and stevioside production. The symptoms we re: yellowing with -N; dark green leaves with -P; clorotic, mottled, and ne crotic leaves, with -K; apical necrosis, with -Ca; leaves with clorosis and necrosis in inverted "V" shape, with -Mg, and small pale green leaves, wit h -S. N, K, and Mg deficiencies reduced the leaf growth, therefore the plan t marketable part. Mg deficiency caused greater reduction on the developmen t of the radicular system. N, P, K, and S deficiencies decreased the shoot: root dry weight ratio, while Mg deficiency increased it. All deficiencies d ecreased 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 g ood correlation with the plant nutritional status. The deficiencies of K, C a, and S decreased the concentration of stevioside while all deficiencies, except of P, decreased the stevioside content.