COMPARATIVE PHOTOINHIBITION OF A HIGH AND A LOW-ALTITUDE ECOTYPE OF TOMATO (LYCOPERSICON HIRSUTUM) TO CHILLING STRESS UNDER HIGH AND LOW-LIGHT CONDITIONS

A high altitude ecotype and a low altitude ecotype of tomato (Lycopers icon hirsutum) plants were examined to compare their capacities to res ist chilling-induced photoinhibition. Tomato plants at 5 weeks old wer e acclimated under high light condition of 550 mu mol m(-2) s(-1) at 2 5/20 degrees C (day/night) for 3 days. Acclimated plants were exposed to a temperature of 5/5 degrees C for 3 days with either low light (60 mu mol m(-2) s(-1)) or high light (550 mu mol m(-2) s(-1)). The plant s were allowed to recover under the same conditions as in the acclimat ion. The low altitude ecotype exhibited significantly greater decrease in both quantum yield for O-2 evolution and chlorophyll a fluorescenc e than the high altitude ecotype after 3 days of chilling. This tenden cy became more obvious under high light than under low light condition during the chilling. When both ecotypes were exposed to high light du ring the chilling, the high altitude ecotype accumulated more caroteno id pigments including zeaxanthin than the low altitude ecotype. In chi lling at low light, however, their capacities to accumulate the carote noid pigments were not different. Our results suggest that the high al titude ecotype has a greater capacity to develop its photosynthetic ap paratus to resist chilling-induced photoinhibition through the accumul ation of zeaxanthin as well as photochemical energy dissipation than t he low altitude ecotype, but the non-radiative energy dissipation is r equired less during chilling under low light condition. (C) 1998 Elsev ier Science Ireland Ltd. All rights reserved.