Overall, drought and unfavourable temperatures are the major climatic limitations for coffee production. These limitations are expected to become increasingly important in several coffee growing regions due to the recognized changes in global climate, and also because coffee cultivation has spread towards marginal lands, where water shortage and unfavourable temperatures constitute major constraints to coffee yield. In this review, we examine the impacts of such limitations on the physiology, and consequently on the production of mainly Coffea arabica and C. canephora, which account for about 99 % of the world coffee bean production. The first section deals with climatic factors and the coffee plant's requirements. The importance of controlling oxidative stress for the expression of drought and cold tolerance abilities is emphasized in the second section. In the third section, we examine the impacts of drought on cell-water relations, stomatal behaviour and water use, photosynthesis and crop yield, carbon and nitrogen metabolism, root growth and characteristics, and on drought tolerance. In the fourth section, the impacts of low positive and high temperatures on coffee physiology are discussed; some insights about effects of negative temperatures are also presented. Finally, the last section deals with shading in harsh environments as a mean of buffering climatic fluctuations, as well as of increasing environmental sustainability in coffee exploitation. Key words: Coffea, chilling, frost, heat, photosynthesis, water deficit, water use, yield.Impactos da seca e do estresse térmico sobre a fisiologia e a produção do cafeeiro: uma revisão: De modo geral, seca e temperaturas desfavoráveis são as principais limitações climáticas à produção do cafeeiro. A importância de tais limitações deve aumentar, em função das mudanças reconhecidas no clima global e, também, porque a cafeicultura vem sendo expandida para regiões marginais onde secas e temperaturas desfavoráveis se constituem em grandes limitações à produção do café. Nesta revisão, analisam-se os impactos de tais limitações sobre a fisiologia, e por extensão sobre a produção, principalmente de Coffea arabica e C. canephora, que respondem por cerca de 99 % da produção mundial. A primeira seção deste trabalho aborda as exigências climáticas do cafeeiro. Na segunda seção, enfatiza-se a importância do controle do estresse oxidativo para a expressão da capacidade de tolerância à seca e ao frio. Na terceira, examinam-se os impactos da seca sobre as relações hídricas em nível celular, comportamento estomático e uso da água, fotossíntese e produção, metabolismo do carbono e do nitrogênio, caracterís-ticas e respostas de crescimento das raízes, além da tolerância à seca. Na quarta seção, discutem-se impactos tanto de baixas temperaturas positivas como de altas temperaturas sobre a fisiologia do cafeeiro; apresentam-se, também, algumas informações sobre efeitos de temperaturas negativas. Finalmente, na última seção, discute-se sobre o sombreamento como um meio de tamponament...
After oil, coffee is the most valuable traded commodity worldwide. In this review we highlighted some aspects of coffee growth and development in addition to focusing our attention on recent advances on the (eco)physiology of production in both Coffea arabica and C. canephora, which together account for 99% of the world coffee bean production. This review is organized into sections dealing with (i) climatic factors and environmental requirements, (ii) root and shoot growth, (iii) blossoming synchronisation, fruiting and cup quality, (iv) competition between vegetative and reproductive growth and branch die-back, (v) photosynthesis and crop yield, (vi) physiological components of crop yield, (vii) shading and agroforestry systems, and (viii) high-density plantings. Key words: arabica, conilon and robusta coffee, beverage quality, density planting, die-back, flowering, photosynthesis, shading Ecofisiologia do crescimento e da produção do cafeeiro: O cafeeiro, depois do petróleo, é a principal mercadoria comercializada no mundo. Nesta revisão, analisam-se aspectos do crescimento e desenvolvimento do cafeeiro, dandose, também, ênfase aos avanços recentes sobre a (eco)fisiologia da produção de Coffea arabica e C. canephora, que respondem por cerca de 99% da produção mundial de café. Abordam-se (i) os fatores climáticos e requerimentos ambientes, (ii) crescimento da parte aérea e das raízes, (iii) sincronização da floração, frutificação e qualidade da bebida, (iv) competição entre os crescimentos vegetativo e reprodutivo e ocorrência de seca de ramos; (v) fotossíntese e produção, (vi) componentes fisiológicos da produção, (vii) sombreamento e sistemas agroflorestais, e (viii) plantios adensados. Palavras-chave: cafeeiros arábica, conilon e robusta, fotossíntese, floração, qualidade de bebida, seca de ramos, sombreamento
The tropical coffee crop has been predicted to be threatened by future climate changes and global warming. However, the real biological effects of such changes remain unknown. Therefore, this work aims to link the physiological and biochemical responses of photosynthesis to elevated air [CO2 ] and temperature in cultivated genotypes of Coffea arabica L. (cv. Icatu and IPR108) and Coffea canephora cv. Conilon CL153. Plants were grown for ca. 10 months at 25/20°C (day/night) and 380 or 700 μl CO2 l(-1) and then subjected to temperature increase (0.5°C day(-1) ) to 42/34°C. Leaf impacts related to stomatal traits, gas exchanges, C isotope composition, fluorescence parameters, thylakoid electron transport and enzyme activities were assessed at 25/20, 31/25, 37/30 and 42/34°C. The results showed that (1) both species were remarkably heat tolerant up to 37/30°C, but at 42/34°C a threshold for irreversible nonstomatal deleterious effects was reached. Impairments were greater in C. arabica (especially in Icatu) and under normal [CO2 ]. Photosystems and thylakoid electron transport were shown to be quite heat tolerant, contrasting to the enzymes related to energy metabolism, including RuBisCO, which were the most sensitive components. (2) Significant stomatal trait modifications were promoted almost exclusively by temperature and were species dependent. Elevated [CO2 ], (3) strongly mitigated the impact of temperature on both species, particularly at 42/34°C, modifying the response to supra-optimal temperatures, (4) promoted higher water-use efficiency under moderately higher temperature (31/25°C) and (5) did not provoke photosynthetic downregulation. Instead, enhancements in [CO2 ] strengthened photosynthetic photochemical efficiency, energy use and biochemical functioning at all temperatures. Our novel findings demonstrate a relevant heat resilience of coffee species and that elevated [CO2 ] remarkably mitigated the impact of heat on coffee physiology, therefore playing a key role in this crop sustainability under future climate change scenarios.
Transgenic tomato (Solanum lycopersicum) plants expressing a fragment of the Sl SDH2-2 gene encoding the iron sulfur subunit of the succinate dehydrogenase protein complex in the antisense orientation under the control of the 35S promoter exhibit an enhanced rate of photosynthesis. The rate of the tricarboxylic acid (TCA) cycle was reduced in these transformants, and there were changes in the levels of metabolites associated with the TCA cycle. Furthermore, in comparison to wild-type plants, carbon dioxide assimilation was enhanced by up to 25% in the transgenic plants under ambient conditions, and mature plants were characterized by an increased biomass. Analysis of additional photosynthetic parameters revealed that the rate of transpiration and stomatal conductance were markedly elevated in the transgenic plants. The transformants displayed a strongly enhanced assimilation rate under both ambient and suboptimal environmental conditions, as well as an elevated maximal stomatal aperture. By contrast, when the Sl SDH2-2 gene was repressed by antisense RNA in a guard cell-specific manner, changes in neither stomatal aperture nor photosynthesis were observed. The data obtained are discussed in the context of the role of TCA cycle intermediates both generally with respect to photosynthetic metabolism and specifically with respect to their role in the regulation of stomatal aperture.
With irrigation, plant hydraulic conductance (K(L)), midday psi(x) and total biomass were all greater in clones 109A and 120 than in the other clones. Root mass to leaf area ratio was larger in clone 109A than in the others, whereas rooting depth was greater in drought-tolerant than in drought-sensitive clones. Predawn psi(x) of -3.0 MPa was reached fastest by 109A, followed progressively by clones 46, 120 and 14. Decreases in g(s) with declining psi(x), or increasing evaporative demand, were similar for clones 14, 46, and 120, but lower in 109A. Carbon isotope ratio increased under drought; however, it was lower in 109A than in other clones. For all clones, psi(x), g(s) and K(L) recovered rapidly following re-watering. Differences in root depth, K(L) and stomatal control of water use, but not osmotic or elastic adjustments, largely explained the differences in relative tolerance to drought stress of clones 14 and 120 compared with clones 46 and 109A.
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