Thermal Adaptation of Pennisetum: Leaf Photosynthesis and Photosynthate Translocation

Abstract

Leaf photosynthetic rates, loss of photosynthate ¹⁴C, sucrose concentrations and invertase activities were measured in three genotypes of Pennisetum growing at daylnight temperatures that ranged from 18/13 to 33/28°C. Leaves at low temperature had low photosynthetic rates, exported ¹⁴C more slowly, retained a higher proportion of photosynthate ¹⁴C, had higher sucrose concentrations and aged (physiologically) more slowly than did leaves growing at higher temperatures. The genotype that retained most photosynthate in the source leaves was the most cold-intolerant whereas there was no correlation between photosynthetic rates and previously observed growth rates.