Temperature increase assumes a prominent role in the context of expected climate change because of its significant impact on plant metabolism. High temperature can affect the carbon-assimilation pathway at both stomatal and non-stomatal levels, mainly through stomatal closure and photochemical and biochemical limitations. In general, however, plants have some ability to trigger acclimation mechanisms to cope with stressful conditions, especially if the limitations are imposed in a gradual manner during seasonal change. This study aims at evaluating changes at stomatal and photochemical levels in Coffea arabica and C. canephora under exposure to mild temperature (spring) and high temperature (summer). Potted plants were maintained in a greenhouse, watered to field capacity and subject to natural variations of light, temperature and relative humidity. In C. arabica, exposure to summer conditions decreased photosynthetic rates (A), stomatal conductance (gs) and stomatal density and increased intrinsic water-use efficiency (iWUE) compared with spring values, whereas C. canephora plants maintained similar values in both seasons. However, C. canephora presented lower A and gs during spring than C. arabica. Because photosynthetic capacity (Amax), photosynthetic performance index and membrane permeability were similar between genotypes and seasons, and maximum quantum yield (Fv/Fm) and photosynthetic pigments were not affected in C. arabica in summer, we conclude that under high temperature conditions, stomatal closure imposes the major limitation on C. arabica photosynthesis in summer. Finally, both coffee genotypes were able to avoid damage to photochemistry pathway under supra-optimal temperatures.

RESUMO-Estudou-se o comportamento de plantas de mamoeiro (Carica papaya L. cvs. Sunrise Solo e Tainung 1) crescidas em bandejas de poliestireno (72 células) com substrato (Plantmax Hortaliças = casca de pínus + vermiculita + turfa), adicionado de 4% de adubo orgânico (húmus; esterco de gado e Nutriplanta) combinado com 0,05% de adubo químico (Osmocote NPK 14-14-14 de liberação lenta e NPK 14-14-14 de liberação normal). A germinação das sementes do híbrido Tainung 1 iniciou-se aos 12 dias após a semeadura em todos os tratamentos, e da cultivar Sunrise Solo, aos 14 dias. A cultivar Sunrise Solo e o híbrido Tainung 1 apresentaram maior taxa de germinação nos substratos adubados com Osmocote e fonte orgânica de húmus e esterco bovino, respectivamente. As mudas de mamoeiros Tainung 1 e Sunrise Solo crescidas nos substratos contendo Osmocote apresentaram melhor desenvolvimento do que nos substratos com formulado NPK (14-14-14) de liberação normal. Apesar dos bons resultados apresentados pelas mudas de Sunrise Solo e Tainung 1 nos tratamentos constituídos de Nutriplanta, não foi verificada diferença significativa entre os substratos contendo adubos orgânicos. As mudas desenvolvidas em substrato contendo esterco de curral + NPK de liberação normal tiveram os piores resultados para a maioria das características analisadas (altura, diâmetro do caule, peso seco da parte aérea, caule e raiz, e área foliar total). Os teores de nutrientes (NPK) encontrados na análise foliar das amostras foram superiores nos tratamentos com Osmocote em relação aos demais, cerca de 20% para o híbrido Tainung 1 e 10% para o Sunrise Solo. Termos para indexação: Carica papaya, cultivares, húmus, esterco. DIFFERENT GROWTH MEDIUM AND FERTILIZER EFFECTS ON PAPAYA SEEDLINGS GROWTHABSTRACT-The behavior of papaya (Carica papaya L. cv. 'Sunrise Solo' and 'Tainung 1') seedlings grown in polystyrene trays (72 cells) in the growth medium (Plantmax = pine bark + vermiculite + peat) amended with 4% of organic fertilizer (Humus; composted cattle manure and Nutriplanta) combined with 0.05% of inorganic fertilizer (Osmocote -slow release -NPK 14-14-14 and normal release NPK 14-14-14) was evaluated in this study. Germination in cv. 'Sunrise Solo' and hybrid 'Tainung 1' occurred 12 and 14 days after sowing, respectively. Higher germination rate in both materials was obtained in the growth medium fertilized with Osmocote plus humus and composted cattle manure, respectively. The seedlings fertilized with slow release type hastened growth compared with normal one. Growth medium amended with Nutriplanta gave good results but there was no significant difference with others organic fertilizers. The seedlings grown in growth medium amended with composted cattle manure + normal release NPK showed the poorest results in almost all analyzed parameters such as height, stem diameter, dry weight -root and top -and total leaf area. The nutrient contents (NPK) found in the leaf analyses samples were higher in treatments using slow release fertilizer (~20% for hybrid T...

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The economics of coffee plantations is intrinsically linked to pruning, which can improve the canopy architecture and thereby increase productivity. However, recommended pruning times on conilon coffee plantations have been made on an entirely empirical basis. In this study, by evaluating growth, photosynthetic gas exchanges, starch accumulation and crop productivity, the effects of pruning at different times between harvest and flowering were investigated for six conilon coffee clones with distinct stages of fruit maturation (early, intermediate and late). Clones with an early maturation stage were pruned at four different times: 0, 30, 60 and 90 days after harvest (DAH). Intermediate clones were pruned at 0, 30 and 60 DAH, and late clones were pruned at 0 and 30 DAH. Overall, the rates of shoot growth and net photosynthesis, the stomatal conductance and the crop yield were not affected by the pruning treatments in any of the clones. In addition, pruning times did not affect the concentrations of starch or the photochemical efficiency of photosystem II. The carbon isotope composition ratio was marginally affected by the treatments. These results suggest that the pruning time after harvests is relatively unimportant and pruning operations can be scheduled to optimise the use of labour, which directly impacts the production costs of coffee. I N T RO D U C T I O NAfter oil products, coffee is the second most commonly traded commodity worldwide. On a broader scale, when all steps from cultivation to the sale of final consumable products are considered, the international coffee trade involves approximately 500 million people (DaMatta et al., 2010). Of the approximately 100 species of the genus Coffea (Davis et al., 2006), only C. arabica L. (arabica coffee) and C. canephora Pierre ex A. Froehner (robusta coffee) are economically important worldwide; these two species are responsible for 99% of world bean production. Currently, arabica