ISHS Acta Horticulturae 343: Physiological Basis of Postharvest Technologies
A REASSESSMENT OF HEAT STRESS AS A MEANS OF REDUCING CHILLING INJURY IN TOMATO FRUIT |
| Author: | B.D. Whitaker |
| Abstract:
A recent study indicated that heat stress confers tolerance to chilling in tomato fruit. Partial ripening of tomato has also been shown to reduce chilling sensitivity. To test the relative merits of these "treatments", tomatoes were held 3 days at ripening or heat-stress temperature (20 vs 38C), chilled for 20 days at 5C, and assessed for ripening and injury over 7 subsequent days at 20C. Based on color (a*) values, lycopene content, rates of CO2 and C2H4 evolution, and visible injury, heat-treated (38C) fruits sustained more chilling injury and ripened much more slowly than the 20C controls. These results show that, under certain conditions, heat treatment of tomato fruit may not reduce chilling injury as effectively as partial ripening. Exposure of plant tissues to high temperature stress for several hours or more often induces a heat-shock response characterized by reduced total protein synthesis coincident with production of specialized heat-shock proteins (HSP) (Lafuente et al., 1991; Lurie and Klein, 1991). HSP confer thermotolerance, such that subsequent exposure to a normally lethal high temperature causes little damage (Lafuente et al., 1991; Lurie and Klein, 1991). Subjecting plants to one form of stress can sometimes confer greater tolerance to other stresses, and a common aspect of the response to different stresses is a change in the pattern of protein synthesis (Lafuente et al., 1991; Lurie and Klein, 1991; Klein and Lurie, 1992). Recently, there have been several reports on the use of high temperature treatments to improve quality or to extend the storage life of fruits (Lurie and Klein, 1991; Klein and Lurie, 1992; Klein and Lurie, 1990; Mitchem and McDonald, 1992). In one study, it was found that a 3 day heat treatment of mature-green tomato fruit prior to 3 weeks of storage at 2C resulted in delayed but otherwise normal ripening after return to 20C, whereas control fruit stored at 2C at harvest developed chilling injury (CI) and ripened poorly after rewarming (Lurie and Klein, 1991). A question not addressed by this study was what are the effects of 3 days postharvest at a "ripening temperature" (20C) before low temperature storage. Maturity is an important determinant of susceptibility to Cl, and partial ripening reduces chilling sensitivity in tomato and other fruits (Autio and Bramlage, 1986). Hence, in the present investigation, mature-green tomato fruit were held 3 days at ripening or heat-stress temperature (20 vs 38C), chilled for 20 days at 5C, and assessed for ripening and injury 7 days after return to 20C. Based on chromaticity (a*) values, lycopene content, rates of CO2 and C2H4 evolution, and visible injury (pitting on the shoulders), heat-treated (38C) fruits sustained more chilling injury and ripened much more slowly than the 20C controls. Color (a*) values determined for control fruit after 3 days at 20C indicated ripening to the breaker stage, whereas fruit heat stressed at 38C for 3 days had not ripened. Seven days after rewarming chilled fruit to 20C, the control. | |
Download Adobe Acrobat Reader (free software to read PDF files) | |
