The use of shading and paclobutrazol in coffee plants can be an important cultivation strategy to mitigate the negative effects of high solar radiation and atmospheric temperature. Therefore, the levels of photosynthetic pigments and foliar gas exchanges of young coffee plants submitted to doses of paclobutrazol were evaluated, in environments with artificial light restriction. Five experiments were performed: one in full sunlight and four in artificially shaded environments with black polyethylene meshes at 20%, 40%, 60% and 80% levels of light restriction. In each of these environments, an experiment was carried out, consisting of five treatments, defined by the application of paclobutrazol via substrate, at doses of 0, 10, 20, 30 and 40 mg of active ingredient per plant. Joint analysis of experiments and analysis of variance of the regression were made, for the study of levels of shading and doses of paclobutrazol. The light restriction optimized the photosynthetic apparatus of the plants, mainly at levels close to 60%, and considerably favored leaf gas exchanges of arabica coffee. The application of paclobutrazol in the studied dosages resulted in little or no effect on photosynthetic pigment contents and did not influence leaf gas exchanges of coffee plants.

Atualmente, os serviços ambientais relativos aos sistemas agroflorestais (SAFs) estão fundamentados em aspectos qualitativos. Entretanto, para que ocorra a consolidação do pagamentos por tais serviços, os diversos fatores que condicionam os SAFs necessitam ser caracterizados. Este estudo teve comoobjetivos analisar se o estoque de biomassa individual de cafeeiros é afetado porSAFs caracterizados por manejo e arranjos distintos dos cafeeiros arábica e das grevíleas, além de verificar se haveria possibilidade de ajuste de equações alométricas para estimar a biomassa seca dos cafeeiros.O experimento foi conduzido em sistemas de cultivo de café (Coffea arabica L.) sob manejo orgânico e convencional arborizado por grevíleas (Grevillea robusta A. Cunn.), localizados nas regiões do Planalto da Conquista e Chapada Diamantina, Bahia. A partir da determinação da biomassa pelo método destrutivo da simples separação, foram estabelecidas equações de estimativa do estoque de biomassa individual dos cafeeiros. Concluiu-se que o sistema de manejo orgânico e convencional são fatores de menor impacto para o acúmulo de biomassa e carbono em relação à fatores como a densidade de cafeeiros e o arranjo das grevíleas. O menor adensamento de cafeeiros é fator que determina a superioridade dos estoques de biomassa individual.A densidade de cafeeiros e arranjo das grevíleas são fatores que determinam modelos alométricos diferenciados para a estimativa de biomassa dos cafeeiros.

Agroforestry systems are important forms of sustainable farming, providing several ecosystem services. However, characterization and management of factors such as thermal and light heterogeneity, as well as interactions between trees and coffee plants, are determinants for achieving the desired sustainability. This study aimed to verify whether different distances between Coffea arabica L. and Australian red cedar can change soil and microclimate characteristics and how they alter morphological and physiological attributes of coffee plants over the rainy season and a prolonged drought period (veranico) in Summer. The trial was carried out in the municipality of Barra do Choça, in an area with Australian red cedar trees (Toona ciliata M. Roem), distributed in two hedges, spaced 19.8 × 3 m apart, in a northeast-southwest direction, and coffee plants var. Catucaí Vermelho (3.3 × 0.5 m). Treatments were defined by the distance between the coffee plants and the first row of the Australian red cedar hedge (3.3 m, T1; 6.6 m, T2; 9.9 m, T3; 13.2 m, T4; 16.4 m, T5). Morphology and physiology of coffee plants, soil temperature, incident light on coffee plants, and the allelopathic potential of Australian red cedar leaf extracts were assessed in the wet and dry season of the 2016–2017 Summer. Temperatures fluctuated less in experimental units close to the hedge. The reduced growth of coffee plants close to the hedges was related to self-shading associated with light restriction by the trees. The experiment showed the allelopathic potential of Australian red cedar leaves.

Coffee (Coffea arabica L.) plants have been assorted as highly suitable to growth at elevated [CO2] (eCa), although such suitability is hypothesized to decrease under severe shade. We herein examined how the combination of eCa and contrasting irradiance affects growth and photosynthetic performance. Coffee plants were grown in open-top chambers under relatively high light (HL) or low light (LL) (9 or 1 mol photons m−2 day−1, respectively), and aCa or eCa (437 or 705 μmol mol–1, respectively). Most traits were affected by light and CO2, and by their interaction. Relative to aCa, our main findings were (i) a greater stomatal conductance (gs) (only at HL) with decreased diffusive limitations to photosynthesis, (ii) greater gs during HL-to-LL transitions, whereas gs was unresponsive to the LL-to-HL transitions irrespective of [CO2], (iii) greater leaf nitrogen pools (only at HL) and higher photosynthetic nitrogen-use efficiency irrespective of light, (iv) lack of photosynthetic acclimation, and (v) greater biomass partitioning to roots and earlier branching. In summary, eCa improved plant growth and photosynthetic performance. Our novel and timely findings suggest that coffee plants are highly suited for a changing climate characterized by a progressive elevation of [CO2], especially if the light is nonlimiting.

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