Effect of Foliar Application of Humic Acid and Zinc Sulfate on Vegetative, Physiological, and Biochemical Characteristics of Physalis alkekengi L. Under Soilless Culture

Physalis alkekengi L. belonging to Solanaceae family has been widely used due to its medicinal properties. The aim of this work was to investigate the effects of foliar application of humic acid and zinc sulfate fertilizers either separately or simultaneously on vegetative, physiological, biochemical characteristics, and alkaloid content of Physalis alkekengi L. This study was conducted under soilless culture (cocopeat: perlite 1:1) in a research greenhouse with a factorial approach based on a completely randomized design with 3 replications, each including three pots each pot containing one plant. Humic acid solution was applied at three levels (0, 1, and 2 g L −1 ) and zinc sulfate at three levels (0, 0.5, and 1 g L −1 ) as foliar application. The results showed that the concentrations of 0.5 and 1 g L −1 of zinc sulfate along with 2 g L −1 humic acid increased all parameters studied of Physalis alkekengi . The highest alkaloid content of root was obtained using 0.5-g L −1 zinc sulfate and 2-g L −1 humic acid simultaneously, while the highest amount of leaf alkaloids was obtained in the simultaneous treatment of 2-g L −−1 humic acid and 1-g L −1 zinc sulfate. Root alkaloid content had a positive and significant correlation with leaf alkaloid content, and foliar fertilization of Physalis plants with humic acid and zinc sulfate simultaneously had a significant effect on biochemical and physiological characteristics of plants. We hope that foliar application of humic acid and zinc sulfate can be considered as an efficient strategy to enhance nutrition and production of secondary metabolites in medicinal plants.