Tissue culture propagation of the Cactaceae as influenced by plant growth regulators with scannning electron microscopy sequences of lateral meristems and spine initiation and development of Mammillaria elongata (Cactaceae)

Vita.Tubercle, areole, and stem section explants of Mammillaria elongata, Opuntia polyacantha, Weberocereus biolleyi, and other cacti were cultured on a supplimented Murashige and Skoog high salts medium. Various concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D), naphthaleneacetic acid (NAA), indolebutyric acid (IBA), 6- furfurylamino purine (Kinetin), 6-(dimethylallylamino)- purine (2-IP), 6-benzylaminopurine (BAP), and gibberellic acid (GAj) were used in gradient and factorial experiments to determine the optimum ratio of auxins and cytokinins. The optimum auxin:cytokinin balance varied with species depending upon the type of response desired. Cacti explants exhibited the classic auxin:cytokinin response in that auxins promoted rooting and cytokinins promoted shoot formation. Of the three species investigated in detail (M. elongata, 0. polyacantha, and W. biolleyi), NAA (10.0 to 60.0 mg/1) and IBA (10.0 to 100.0 mg/1) yielded the optimum rooting response. Shoot formation was promoted by BAP (10.0 to 80.0 mg/1), 2-IP (20.0 to 60.0 mg/1 for M. and 0.), and Kinetin (20.0 mg/1 for M. only). Callus proliferation and fresh weight increase were promoted by the same concentrations of growth regulators; 2,4-D (0.1 to 60.0 mg/1), NAA (0.4 to 40.0 mg/1), and IBA (40.0 to 80.0 mg/1 for W. only). The addition of maleate buffer reduced the response of 0. polyacantha explants to the various growth regulators