Abstract: All organisms respond to elevated temperature by specifically inducing the expression of a set of new proteins; the "heat shock proteins" or "Hsps." Although this response has been known for over thirty years, the specific role of individual heat shock proteins in the overall response is still largely unknown. All organisms have a basal level of thermotolerance--an organism-specific temperature threshold above which they die. The advantage to increased thermotolerance in a plant is clear--increased thermotolerance improves crop yield in particularly hot growing seasons, and expands the geographic area where a particular crop can be grown. The present invention provides a method of increasing thermotolerance in plants comprising transforming plant cells with a vector which over-expresses the carrot Hsp17.7 gene. This is the first demonstration of enhancement of plant thermotolerance through the over-expression of a low molecular weight heat shock protein.