Low positive temperatures are of up most importance in tropical plant species, namely in Coffea spp., disturbing plant growth and metabolism, with impact on photosynthesis and yield. An integrated biochemical and molecular approach was used to analyze the cold impact and tolerance ability on photosynthesis of coffee plants, linked to modifications of the status of the antioxidative system, and chloroplast membrane lipids. Five coffee genotypes with contrasting cold sensitivity were used: Coffea canephora cv. Apoatã, C. arabica cv. Catuaí, C. dewevrei, Icatu (C. arabica x C. canephora) and Piatã (C. dewevrei x C. arabica). Determinations were performed along a slow cold imposition (to allow acclimation) from 25/20 ºC (day/night) down to 13/8 ºC, after exposure to 4o C (chilling) and in the rewarming period thereafter. Cold exposure strongly affected net photosynthesis in all genotypes, although stomatal limitations were not detected. Icatu revealed the lowest leaf loss, higher reinforcement of the antioxidative system, qualitative changes in chloroplast membrane lipids and regulation of some key genes. Altogether these responses indicate a better ability of this genotype to cope with low positive temperatures

Doutoramento em Biologia - Instituto Superior de Agronomia