Autoria: RAKOCEVIC, M.; BATISTA, E. R.

Resumo: Trends in climate changes indicate that the air [CO2] will continue to increase. The first plant response to elevated [CO2] (e[CO2]) is the increased photosynthetic rate. Photosynthetic rate dependence on light (A/PAR curves) is characterized by several parameters, often used to determine plant species responses to environment and phenological plasticity. The effects of water supply and phenological stage were expected, with no acclimation after long-term Coffea arabica L. cultivation under e[CO2]. The aim of the study was to determine variations in parameters of A/PAR curves in coffee leaves over a tree vertical profile after long-term cultivation under free-air-CO2-enrichment (FACE) system. The p arameters of A/PAR curves in C. arabica were estimated after five-years cultivation in FACE under two CO2 conditions, actual (a[CO2], ~390?L CO2 L-1) and e[CO2] (~590?L CO2 L-1), in two water regimes (rainfed and irrigation). The A/PAR curves were estimated in two phenological stages (grain formation - February 2016 and fruit maturation - May 2016). The A/PAR responses were determined by varying photosynthetic active radiation (PAR) from 1117 to 0 ?mol photons m?2 s?1 in four 50 cm-thick layers of vertical plant profile. The maximum photosynthesis (Amax), dark respiration (Rd), apparent quantum efficiency (?), and light compensation point (?) generally increased under e[CO2] compared to a[CO2], showing higher values during grain formation than during fruit maturation (Figure 1). The Rd and ? followed the progressive increase by layers only during the grain formation (Figures 1C and 1E). Continuation in e[CO2] stimulation indicated that leaf photosynthesis acclimation did not occur after five-years coffee cultivation under FACE. The lack of progressive increase in Amax, ? and ? over vertical profile indicates leaf plasticity to light availability, especially considering the high Amax of the two lowest layers. The compensation effects of e[CO2] to low water availability were observed in all A/PAR responses.

Ano de publicação: 2019

Tipo de publicação: Resumo em anais e proceedings

Unidade: Embrapa Meio Ambiente

Palavras-chave: Amax, Coffea Arábica, Elevated CO2, FACE experiment, Mudança Climática, Seca