Effect of gibberellins on growth and biochemical constituents in Chlorella minutissima (Trebouxiophyceae)

Stirk W.A.,Tarkowská D., Grúz J.,Strnad M.,Ördög V.,van Staden J.

Keywords: proteins
Abstract: A hormonal network regulates growth processes and stress responses in vascular plants. There is evidence for a similar hormonal network in microalgae. This study investigated the effect of exogenous gibberellins (GAs) on Chlorella minutissima Fott et Nováková growth and biochemical composition. Two bioactive GAs i.e. GA3 and GA4 were applied at 10−8–10−5 M. Growth was monitored until cultures were harvested on day 7 when in an exponential growth phase. Primary metabolites (protein, chlorophyll and carotenoids) were quantified and endogenous GAs and phenolic acids were identified and quantified. GA3 had little beneficial effect on growth in C. minutissima while GA4 was inhibitory. GA application had little effect on the protein, chlorophyll and total carotenoid content. Analysis of the GA content suggested that GA3 was not readily taken up by the cells while GA4 was absorbed but not further metabolised. This high accumulation of GA4 could account for its inhibitory effect. Three phenolics acids were detected in C. minutissima i.e. p-hydroxybenzoic acid > salicylic acid > protocatechuic acid. Their concentrations were not affected by GA treatments or GA-type. The physiological role of GAs in microalgae is still unclear and further studies are required to gain clearer insight into uptake rates, metabolism and function.
DOI: 10.1016/j.sajb.2019.05.001 IEB authors: Jiří Grúz, Miroslav Strnad, Danuše Tarkowská