Auxin and cytokinin combinations improve growth rates and protein contents in Laurencia catarinensis (Rhodophyta)

Laurencia catarinensis (Ceramiales, Rhodomelaceae) has a high diversity of secondary metabolites such as acetogenin and halogenated terpenoids, with biological activities. We tested different combinations of auxins and cytokinins to evaluate their effects on the growth, total soluble proteins, pigments, and carbohydrates of L. catarinensis with the aim of improving the culture techniques of this species. To accomplish this, algae were cultivated in seawater enriched with quarter strength of von Stosch solution (VSES/4) with the addition of plant growth regulators (PGRs), and the treatment control without PGRs addition. The auxins tested were indole-3-acetic acid (IAA) and 2,4-dichlorophenoxyacetic acid (2,4-D), and cytokinins were benzylaminopurine (BA) and 2-isopentenyladenine (2iP), in the following combinations: IAA:BA, IAA:2iP, 2,4-D:BA, and 2,4-D:2iP, in the concentrations of 5:5, 5:50, 50:5, and 50:50 mu M for each auxin:cytokinin combination. Addition of PGRs had significant effects on the growth rates of L. catarinensis, which varied from 7.62 +/- 0.12% to 9.30 +/- 0.55% day(-1). The highest growth rates were observed in treatments with 5:5 mu M of IAA:BA and 2,4-D:BA, and 50:5 mu M of 2,4-D:2iP. Higher contents of total soluble proteins were observed in treatments with 50:50 mu M of IAA:BA and 2,4-D:BA. The auxin:cytokinin combinations inhibited allophycocyanin contents, but did not affect chlorophyll a and carbohydrate concentrations. Therefore, supplementation of auxins and cytokinins, especially the IAA:BA and 2,4-D:BA combinations, is useful approach to stimulate growth rates or soluble protein contents of L. catarinensis, improving the cultivation of this species with high biotechnological potential.