Interaction of [(3)H] gibberellin A 1 with a sub-cellular fraction from lettuce (Lactuca sativa L.) hypocotyls : II. Stability and properties of the association.

Radioactive 2,000 g pellets (2KP) derived from lettuce (Lactuca sativa) hypocotyl sections incubated with [(3)H]gibberellin A1 ([(3)H]GA1) were subjected to a range of treatments to test the stability of labelling. The labelled association was stable in 0.1 M buffer at pH 3 and pH 9 and also in 1 M salt, organic solvents, protease or cellulase. Both 1 M potassium hydroxide (KOH) and a quaternary ammonium hydroxide tissue solubiliser effected an 80% release of incorporated [(3)H]. No radioactivity was released during polyacrylamide gel electrophoresis. Gel chromatography of KOH digests indicated the presence of labelled compounds with a higher molecular weight than GA1. This material remained near to the origin during high-voltage paper electrophoresis. Calculations based upon KOH extraction of 2KP material suggested that 5 to 20% of the total uptake of [(3)H]GA1 could be recovered from this fraction. The implications of these findings are discussed.