Adaptation to chilling: photosynthetic characteristics of the cultivated tomato and a high altitude wild species

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Abstract
When tomato plants of the high‐altitude species Lycopersicon hirsutum and of the cultivated Lycopersicon esculentum were grown at 24/18°C (day/night), the effects of temperature, photon flux density, and intercellular CO2 concentration up to about 600 μl l−1 on net CO2 uptake were similar in the two species. Acclimation of these plants at 12/6°C (day/night) resulted, after 4 d or longer, in a similar downward shift of about 5°C in the optimum temperature for CO2 uptake. However, in comparison with the cultivated species, the high‐altitude plants achieved a higher rate of CO2 uptake at saturating concentrations of intercellular CO2, maintained a higher level of saturating‐light CO2 uptake rate at 10°C after exposure to chilling stress (10°C and photon flux density of 400 μmol m−2s−1 d and 5°C night) for 7–18 d, and displayed a better capacity for rapid recovery after prolonged stress. The greater capacity for CO2 uptake observed in the high‐altitude species during and after exposure to chilling stress was also reflected in its higher growth rate under those conditions compared with plants of L. esculentum. These advantages of the high‐altitude species may partly explain its ability to survive and complete its life cycle under the environmental conditions prevailing in its natural habitat.