Effects of plant growth regulators on growth and morphogenesis in tissue culture of Chondracanthus chamissoi (Gigartinales, Rhodophyta)

Chondracanthus chamissoi (C. Agardh) Kutzing (Gigartinales, Rhodophyta) is an edible species and commercialised for carrageenan production in Chile. Investigations on growth and development are needed to improve its cultivation; therefore, this study aims to evaluate the effects of plant growth regulators (PGRs) on its growth and morphogenesis. PGRs tested were two auxins [indole-3-acetic acid (IAA) and 2,4-dichlorophenoxyacetic acid (2,4-D)] and one cytokinin (benzylaminopurine (BA)) in concentrations of 0.5, 5.0 and 50.0 mu M. These PGRs were added to seawater enriched with half strength of von Stosch solution and were gelled with 0.6 % agar, and treatment control (without PGR addition) was conducted simultaneously. Apical and intercalary segments were used as initial explants. Each treatment was tested with six replicates of five axenic explants, and statistical analyses were performed. After culturing in a solid medium for 10 weeks to induce growth and callus formation, explants were cultured in liquid medium with the same experimental conditions for 10 weeks. Effects of auxins (IAA and 2,4-D) and the cytokinin BA on growth rates of apical segments of C. chamissoi were not significant, while low concentration of IAA stimulated the growth of intercalary segments. On the other hand, high concentrations of BA and IAA stimulated the callus formation in apical and intercalary segments, respectively. In liquid medium, PGR did not have a significant effect on growth rates of apical segments, while 2,4-D in concentrations from 0.5 to 50.0 mu M stimulated growth of intercalary segments, and formation of lateral branches was stimulated by low 2,4-D in apical segments. These results suggest that PGRs have a regulatory role on callus formation and growth of specific explants of C. chamissoi. Furthermore, the formation of lateral branches stimulated by auxin could be used for seedling production under controlled conditions and could improve the micropropagation and cultivation of C. chamissoi in the Chilean coast.