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The objective of this work was to evaluate photoprotective mechanisms related to low positive temperatures in Coffea canephora (Conilon clones 02 and 153) and C. arabica ('Catucaí' IPR 102) genotypes, involved in cold temperature tolerance. To accomplish this, one-year-old plants were successively submitted to: temperature decrease of 0.5ºC day-1, from 25/20ºC to 13/8ºC; a three-day chilling cycle at 13/4ºC; and a recovery period of 14 days (25/20ºC). During the experiment, leaf gas exchange, chlorophyll a fluorescence and leaf photosynthetic pigment content were evaluated. Total activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and ribulose-5-phosphate kinase (Ru5PK) were quantified to measure the activity of photosynthesis key enzymes. All genotypes showed low temperature sensitivity, but displayed diverse cold impact and recovery capabilities regarding the photosynthetic-related parameters studied. Catucaí IPR 102 cultivar showed better ability to cope with cold stress than the Conilon clones, especially Conilon 02, and had full recovery of leaf gas exchange, fluorescence parameters, enzymatic activity, and higher contents of the photoprotective pigments zeaxanthin and lutein. O objetivo deste trabalho foi avaliar mecanismos de fotoproteção relacionados a temperaturas baixas positivas em genótipos de Coffea canephora (clones Conilon 02 e 153) e C. arabica ('Catucaí' IPR 102), envolvidos na tolerância a baixas temperaturas. Para tal, plantas com um ano de idade foram expostas sucessivamente a: decréscimo da temperatura (0,5ºC dia-1), de 25/20ºC até 13/8ºC; um ciclo de três dias a 13/4ºC; e a 14 dias de recuperação (25/20ºC). Durante o experimento, foram avaliadas as trocas gasosas, a fluorescência da clorofila a e os teores de pigmentos fotossintéticos foliares. Foram quantificadas a atividade total da ribulose-1,5-bisfosfato carboxilase/oxigenase (Rubisco) e da ribulose-5-fosfato quinase (Ru5PK), para medir a atividade de enzimas-chave da fotossíntese. Todos os genótipos mostraram sensibilidade a baixas temperaturas, mas tolerância e capacidade de recuperação diferentes no que respeita aos diversos parâmetros fotossintéticos estudados. A cultivar Catucaí IPR 102 apresenta maior capacidade de suportar o estresse do frio que os clones de Conilon, em particular o Conilon 02, com completa recuperação dos parâmetros de trocas gasosas foliares, de fluorescência e das atividades enzimáticas, e teores mais elevados dos pigmentos fotoprotetores zeaxantina e luteína

Low temperature impact on photosynthetic parameters of coffee genotypes