Identification of the phytohormones indole-3-acetic acid and trans-zeatin in microalgae

Abstract

BACKGROUND: Microalgae can biosynthesize phytohormones that promote plant growth and development. These compounds can potentially replace synthetic agricultural inputs that are harmful to the environment. The main plant growth-promoting phytohormones present in microalgae are auxins and cytokinins. The objective of this study was to evaluate the influence of culture conditions (autotrophic and heterotrophic) on the concentrations of the endogenous phytohormones indole-3-acetic acid (IAA) and trans-zeatin (tZ) in the microalgae Chlorella fusca LEB 111, Chlorella vulgaris LEB 112, Scenedesmus obliquus LEB 117, Synechococcus nidulans LEB 115 and Spirulina sp. LEB 18. RESULTS: All microalgae produced IAA and tZ under the three evaluated conditions (autotrophic light/dark (12/12 h), autotrophic continuous light (24 h) and heterotrophic). The IAA concentrations ranged from 1.94 to 56.45 nmol g−1, whereas those of tZ ranged from 0.06 to 35.52 pmol g−1. The cultivation conditions increased the carbohydrate and protein concentrations. Continuous light favored the production of carbohydrates in the studied cyanobacteria (Synechococcus nidulans LEB 115 and Spirulina sp. LEB 18). However, the light/dark condition (12/12 h) afforded the highest protein concentrations for green algae and cyanobacteria. There were no statistically significant differences in the lipid content of the strains studied. CONCLUSIONS: The results of this study are valuable and indicate that the cultivation conditions and species used in this study may be applied in sustainable agriculture, providing alternatives that may contribute to minimizing the environmental impact of synthetic chemical inputs in agriculture. © 2023 Society of Chemical Industry.