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 10 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 matter and carbohydrate content, CO2-exchange and pigment composition. In addition, the susceptibility to dark chilling and temperature dependence of chloroplast electron transport were analyzed by Chl a fluorescence measurements. During 7 days of recovery at 25/20 degrees C subsequent to chilling, the domestic tomato Lycopersicon esculentum (L.) Mill. cv. Abunda exhibited a small capacity for shoot regrowth (39%) compared to the low-altitude wild species L. pimpinellifolium (Jusl.) Mill. PI187002 (82%) and three wild species originating from high altitude: L, peruvianum Mill. LA 385 (92%), L, hirsutum 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 rise (F-R) after 40 h at 0 degrees C and the temperature at which q(P) reached the value 0.5, correlated in general well with the measured differences at whole plant level, measured by the post-chilling regrowth capacity. Chilling resulted in a larger increase in leaf dry matter content in L. esculentum (45%) and L. pimpinellifolium (37%) compared to the high-altitude species (13-16%), which could be attributed to a stronger accumulation of both soluble sugars and starch in mature leaves of the domestic and low-altitude species. Photosynthetic and dark respiration rates during chilling could not account for this difference, The recovery of photosynthesis was better in the high-altitude species, Chl content per unit leaf area decreased more throughout 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 xanthophyll cycle pool on Chl basis, whereas the de-epoxidation state of the xanthophyll cycle increased in the high-altitude wild species. Both responses resulted in increased zeaxanthin levels in chilled leaves of all Lycopersicon species.