Evaluation response of photosynthesis of stevia plant (Stevia rebaudiana Var. Bertoni) to potassium humate and photoperiod

Abstract

For studying the effect of photoperiod and potassium humate in the photosynthesis apparatus of the Stevia plant, an experiment was carried out in factorial arrangement base on completely randomized design with four replications in Mashhad/Iran during 2017. The experiment consisted of three lengths of the day (LD1= natural day, LD2 = 1.5 hours of light more than the natural length of day, and LD3 = 2.5 hours light more than natural day) and potassium humate fertilizer [KH1: zero with KH2: otassium humate (50%)]. The results showed that maximum of photosynthesis was found in KH2×LD2. The most of Ci, quantum yield Fv/Fm value was also found from spraying K-humate in LD2 treatment. The maximum amount of leaf dry weight and biomass was observed in KH2×LD2. The aximum biomasses were also gained in KH2×LD2.