Heat shock induced changes in exocarp soluble sugars of lemons from two climatic regions

Investigations were conducted to ascertain whether the 55 degreesC heat sho ck induced changes in soluble sugars of the exocarp (flavedo) of lemons, Ci trus limon (L.) Burm. F., derived from two distinct climatic growing region s. The exocarp sugars of coastal- and desert-grown lemons were quantitative ly different, but both geographically different lemons responded with sucro se increases to 55 degreesC heat shock of >3 min duration. However, the res ponses were influenced by fruit maturity and seasonal factors. When compari ng the response of coastal- and desert-grown lemons to heat shock treatment , the exocarp sucrose levels were noteworthy. Heat shock significantly incr eased sucrose level of early-season coastal lemon more than mid- to late-se ason lemons. In contrast, late-season desert lemon showed a striking respon se to the heat shock treatment, with a greater increase in sucrose than mid - and early-season lemons. These results suggest a physiological basis for the differential responses to heat treatment of lemons from different geogr aphical regions. The concomitant decreases of glucose and fructose and the sucrose increase with heat shock implied that the sucrose increase may be d erived by synthesis from glucose and fructose.