Phytohormones of microalgae: biological role and involvement in the regulation of physiological processes. Pt II. Cytokinins and gibberellins

Abstract

Literature data on biosynthesis, qualitative and quantitative diversity, involvement in the regulation of physiological and biochemical processes, prospects for use of microalgae cytokinins (CKs) and gibberellins (GA) in biotechnological developments have been analyzed and summarized. Forty-five (45) microalgae species, belonging to 5 divisions, have 37 forms of CKs. The qualitative composition and quantitative content of microalgae CKs are shown to be strongly affected by light conditions and by the presence of an energy source in the culture medium. The main biological functions of microalgae CKs include stimulation of cell division, activation of growth processes, and increased photosynthetic activity. Microalgae cytokinin protective properties that provide protection for cell divisions and the photosynthetic apparatus under stress conditions are revealed. The problem of microalgae cytokinins biosynthesis is still controversial, and their interactions with other phytohormone classes need further investigation. Gibberellins were discovered in 31 microalgae species: 20 hormone isoforms were identified. Microalgae GA physiological effects are similar to those of higher plants, and in a lag phase exhibit reduction and stimulation of cell growth and division, increase in biomass, accumulation of proteins and pigments, and reduction of heavy metal effects.