Increased CO2 and Light Promote in Vitro Shoot Growth and Development of Theobroma cacao

Abstract

Axillary shoots of cacao (Theobroma cacao L.), induced in vitro with cytokinins (BA or TDZ), elongated and produced leaves only in the presence of cotyledons and/or roots. Detached axillary shoots, which do not grow in `vitro under conventional tissue culture protocols, rooted with auxin and developed normally in vivo. Detached axillary shoots from cotyledonary nodes and single-node cuttings from mature plants were induced to elongate and produce normal leaves in the presence of 20,000 ppm CO 2 and a photosynthetic photon flux density (PPFD) of 150 to 200 μmol·s -1 ·m -2 . Subculture nodal cuttings continued to elongate and produce leaves under elevated CO 2 and light levels, and some formed roots. Subculture of microcuttings under CO 2 enrichment could be the basis for a rapid system of micropropagation for cacao. Chemical names used: N -(phenylmethyl) -1 H -purin-6-amine (BA); 1 H -indole-3-butyric `acid (IBA); α -naphthaleneacetic acid (NAA); thidiazuron (TDZ).