HEAT SENSITIVITY OF ESTERASE ISOZYMES IN THE STYLES OF LILIUM AND NICOTIANA

Abstract

SummaryThe heat sensitivity of esterase isozymes in styles was studied by the method of acrylamide gel electrophoresis in nine clones of Lilium and fifteen species of Nicotiana. The material included both self‐incompatible and self‐compatible species, strains or clones, and the Nicotiana species comprised natives of South America, Australia and South Pacific islands.The heat response was highly specific to particular isozymes, the affected isozyme bands usually disappearing completely under treatment while the other bands usually remained unaffected. The remarkable specificity of isozymes to heat is thought to be significant in adaptation of plants to different temperature conditions. This discovery offers the possibility of using the gel electrophoretic technique for identifying heat resistant and heat sensitive genetic eco‐types for breeding high‐yielding varieties specifically suited to different environmental conditions.In Lilium, heat response occurred exclusively in self‐incompatible clones, all self‐compatible clones showing no response. Among the South American Nicotiana species most genotypes in all self‐incompatible species showed heat response and about two‐thirds of the material in self‐compatible species showed at least some response. However, all the examined Australian species and the one South Pacific islands species, which are all self‐compatible, showed no heat response.The heat response in the species of Australia and South Pacific islands is discussed with reference to Waddington's concept of ‘canalization’ and ‘genetic assimilation’. The possible significance of two other general characteristics of isozyme bands in these species, namely, the comparatively lower total number and their generally slower movement in the gel, is considered briefly.