Differential acclimation potential to low temperatures in two species of Lycopersicon: photosynthesis and growth

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Abstract
The effect of growth temperature on the temperature responses of photosynthesis and on growth as estimated from plastochron measurements of L. esculentum, a high-altitude ecotype of L. hirsutum, and their hybrid was studied. The two species and their hybrid displayed similar temperature responses of photosynthesis when they were grown under a thermoperiod of 25:18.degree.C. However, when the growth temperature was decreased to 12:5.degree.C, only L. hirsutum and the hybrid showed the ability to acclimate by increasing their photosynthetic rates at low temperatures. Growth exhibited a similar response to a shift to the low-temperature regime since the growth rate of L. esculentum was reduced to a greater extent than that of L. hirsutum. Moreover, L. hirsutum resumed growth at a faster rate after a short period of time, whereas L. esculentum did not. These results show that there are parallel differences in the capacity of photosynthesis and growth to acclimate to low temperatures below L. esculentum and the high-altitude L. hirsutum.