Differential response of domestic and wild Lycopersicon species to chilling under low light: Growth, carbohydrate content, photosynthesis and the xanthophyll cycle

The response of five Lycopersicon species to 14 days moderate chilling at 1 0 degrees C under low light (75 mu mol m(-2) s(-1)) and subsequent recovery was examined by measurements on relative shoot growth rate, leaf dry matte r and carbohydrate content, CO2-exchange and pigment composition. In additi on, the susceptibility to dark chilling and temperature dependence of chlor oplast electron transport were analyzed by Chl a fluorescence measurements. During 7 days of recovery at 25/20 degrees C subsequent to chilling, the d omestic tomato Lycopersicon esculentum (L.) Mill. cv. Abunda exhibited a sm all capacity for shoot regrowth (39%) compared to the low-altitude wild spe cies L. pimpinellifolium (Jusl.) Mill. PI187002 (82%) and three wild specie s originating from high altitude: L, peruvianum Mill. LA 385 (92%), L, hirs utum Humb, & Bonpl. LA 1777 (67%) and L. chilense Dunn. LA 1970 (71%). The inter-specific differences in chilling sensitivity at the chloroplast level , analyzed by the decline of the maximum rate of induced Chl fluorescence r ise (F-R) after 40 h at 0 degrees C and the temperature at which q(P) reach ed the value 0.5, correlated in general well with the measured differences at whole plant level, measured by the post-chilling regrowth capacity. Chil ling resulted in a larger increase in leaf dry matter content in L. esculen tum (45%) and L. pimpinellifolium (37%) compared to the high-altitude speci es (13-16%), which could be attributed to a stronger accumulation of both s oluble sugars and starch in mature leaves of the domestic and low-altitude species. Photosynthetic and dark respiration rates during chilling could no t account for this difference, The recovery of photosynthesis was better in the high-altitude species, Chl content per unit leaf area decreased more t hroughout the experiment in the domestic and low-altitude species (63-73%) than in their relatives from high altitude (8-29%), In response to chilling , the domestic and low-altitude species showed an increase in the total xan thophyll cycle pool on Chl basis, whereas the de-epoxidation state of the x anthophyll cycle increased in the high-altitude wild species. Both response s resulted in increased zeaxanthin levels in chilled leaves of all Lycopers icon species.