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.

Papaya (Carica papaya L.) is one of the main horticultural crops of many tropical and subtropical regions. The fruit is sold either as a fresh product or processed into drinks, jams, candies, dried and crystallized fruit, while the enzyme papain is used for medicinal purposes. Papaya fruits have high vitamins A and C contents, as well as are good sources of calcium. Brazil is one of the most important producers and exporters of papaya in the world; in 2016 c.a., 1,424,650 tons of papaya was produced in 30,372 hectares of the territory. Optimum light absorption and utilization by the canopy are important factors for maximizing papaya crop growth and productivity. Thus, knowing how papaya responds to light is important to develop management strategies to optimize fruit yield and quality. This short review aims to present the current research knowledge related to the effects of light intensity on the photosynthetic processes and growth of papaya. We demonstrate that photosynthetically active radiation (PAR) greatly affects the physiology of papaya. Understanding the interaction between light and physiological processes is extremely important for a sustainable profitable production under either greenhouse or field conditions. By using improved light science-based management, growers may optimize photosynthetic carbon assimilation and increase papaya yield and fruit quality