Differential response of domestic and wild <i>Lycopersicon</i> species to chilling under low light: growth, carbohydrate content, photosynthesis and the xanthophyll cycle

Abstract

The response of five Lycopersicon species to 14 days moderate chilling at 10°C under low light (75 μmol m −2 s −1 ) and subsequent recovery was examined by measurements on relative shoot growth rate, leaf dry matter and carbohydrate content, CO 2 ‐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°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. &amp; 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°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.