Modeling studies have predicted that coffee crop will be endangered by future global warming, but recent reports highlighted that high [CO2] can mitigate heat impacts on coffee. This work aimed at identifying heat protective mechanisms promoted by CO2 in Coffea arabica (cv. Icatu and IPR108) and Coffea canephora cv. Conilon CL153. Plants were grown at 25/20°C (day/night), under 380 or 700 μL CO2 L−1, and then gradually submitted to 31/25, 37/30, and 42/34°C. Relevant heat tolerance up to 37/30°C for both [CO2] and all coffee genotypes was observed, likely supported by the maintenance or increase of the pools of several protective molecules (neoxanthin, lutein, carotenes, α-tocopherol, HSP70, raffinose), activities of antioxidant enzymes, such as superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), catalase (CAT), and the upregulated expression of some genes (ELIP, Chaperonin 20). However, at 42/34°C a tolerance threshold was reached, mostly in the 380-plants and Icatu. Adjustments in raffinose, lutein, β-carotene, α-tocopherol and HSP70 pools, and the upregulated expression of genes related to protective (ELIPS, HSP70, Chape 20, and 60) and antioxidant (CAT, CuSOD2, APX Cyt, APX Chl) proteins were largely driven by temperature. However, enhanced [CO2] maintained higher activities of GR (Icatu) and CAT (Icatu and IPR108), kept (or even increased) the Cu,Zn-SOD, APX, and CAT activities, and promoted a greater upregulation of those enzyme genes, as well as those related to HSP70, ELIPs, Chaperonins in CL153, and Icatu. These changes likely favored the maintenance of reactive oxygen species (ROS) at controlled levels and contributed to mitigate of photosystem II photoinhibition at the highest temperature. Overall, our results highlighted the important role of enhanced [CO2] on the coffee crop acclimation and sustainability under predicted future global warming scenarios.

The seasonal pattern of vegetative growth is an important feature for evaluation of crop status and its management. The aim of this work was to evaluate the seasonality of vegetative growth of Conilon coffee tree (Coffea canephora Pierre) and its relation with climate variables. The evaluation of vegetative growth rates of three groups of plagiotropic branches and one group of orthotropic branches was performed along one year, in Rio Janeiro state, Brazil. The vegetative growth rates of the branches varied along the period of evaluation, and it seems to be related to the minimum air temperature (in the low growth phase). Higher growth rates were observed when the average of minimum air temperatures was higher than 17ºC and the average of the maximum temperatures lower than 31.5ºC. Below 17ºC the growth rate declined. The branches' growth patterns appeared to be similar, but the plagiotropic branches of different ages presented different rates in the same period of the year, indicating that seasonal growth studies should not be based on a single branch group with the same age. Key words: Coffea canephora, air temperature, stress ResumoO padrão do crescimento sazonal do cafeeiro é um importante auxiliar na avaliação do estado fisiológico e no manejo da cultura. O objetivo do estudo foi avaliar o crescimento vegetativo em Coffea canephora Pierre cv. Conilon e relacionar com fatores climáticos, tendo por base o crescimento de ramos ortotrópicos e plagiotrópicos com diferentes idades. Marcaram-se três grupos de ramos plagiotrópicos e um de ramos ortotrópicos, cuja avaliação de taxa de crescimento foi efetuada durante um ano no Estado do Rio de Janeiro. A taxa de crescimento varia ao longo do ano, o que parece estar relacionado com a temperatura mínima do ar (na fase de baixo crescimento). Foi observada taxa mais elevada quando a média da temperatura mínima do ar foi superior a 17ºC e a média das temperaturas máximas inferior a 31,5ºC. Abaixo de 17ºC a taxa de crescimento dos ramos diminuiu. O padrão sazonal de crescimento dos ramos é semelhante, contudo, os ramos plagiotrópicos de diferentes idades apresentam taxas de crescimento diferentes no mesmo período do ano. Assim, estudos sobre o crescimento vegetativo sazonal dos ramos não deve se basear apenas num grupo de ramos com idades similares. Palavras-chave: Coffea canephora Pierre, temperatura do ar, estresse 1 Engenheiro Agrônomo, Doutor em Produção Vegetal. Professor da