VESSEL VOLUME, GELLING AGENT, AND BASAL SALTS AFFECT PH AND GEL STRENGTH OF AUTOCLAVED TISSUE-CULTURE MEDIA

Effects of autoclaving volume, gelling agent (Bactoagar, Gel-gro, Phyt agar), and basal salts [Murashige and Skoog (MS); Woody Plant Medium ( WPM); Gamborg B5 (GB)] on gel strength and pH of tissue culture media were tested. Gel strength was significantly affected by gelling agent and basal medium. MS media were generally softer than comparable WPM o r GB media. As the vessel volume during autoclaving decreased, gel str ength significantly decreased with Phytagar and Bactoagar gelling agen ts; Gel-gro had greater gel strength at the intermediate volume of med ium autoclaved. In all cases, autoclaving resulted in a pH decrease of 0.2 to 0.5 pH units. Lower pH values were associated with softer gels . The type of gelling agent did not greatly affect the postautoclave p H; mean values among gelling agents were within 0.05 pH units. Postaut oclave pH of MS medium was lower than that of WPM or GB. This study ve rifies the need to observe uniform sterilization protocols to maintain consistency in the chemical and physical properties of media.