Interactive effects of light intensity and pH on growth parameters of a bulbous species (Tulbaghia violacea L.) in hydroponic cultivation and its antifungal activities

Abstract

Tulbaghia violacea L. (Amaryllidaceae) is one of the most harvested bulbous plants of high medicinal value of South Africa in the wild. So far there is no recommended practice of commercial cultivation and knowledge about antimicrobial activity medicinal of this plant species. In this study, we assessed the interactive effects of light intensity and pH on plant growth, nutrient uptake and antifungal activity of extracts of T. violacea, grown under hydroponic environments. Onemonth- old T. violacea plantlets were grown under low (40% shade) and high (0% shade) light intensities in an environmentally-controlled greenhouse with different pH exposures. The effects of light intensity and pH on plant height, plant fresh and dry weights, tissue macro-and micro-nutrient contents as well as antifungal activity (minimum inhibitory concentration [MIC]) were evaluated. The highest dry weight was achieved under the high light intensity treatment (0% shade) combined with the pH 4 treatment (8.29 ± 0.80 g plant-1). Light intensity and pH had significant interactive (DF = 2; P < 0.001) effects on fresh and dry weights. Among the tissue nutrients assessed, only tissue N content was significantly influenced by the interaction between pH and light intensity. Acetone extracts of plants simultaneously grown under the high light intensity and pH 4 produced the best antifungal activity with a mean MIC values range from 0.97 ± 0.18 to 1.50 ± 0.00 mg mL-1 at 18 hr. In conclusion, high light intensity and acidic conditions significantly increased plant biomass and antifungal activity of the plants in hydroponic solution.