Leaf gas exchange and bean quality fluctuations over the whole canopy vertical profile of Arabic coffee cultivated under elevated CO2

Abstract

Leaves in different positions respond differently to dynamic fluctuations in light availability, temperature and to multiple environmental stresses. The current hypothesis states that elevated atmospheric CO2 (e[CO2]) can compensate for the negative effects of water scarcity regarding leaf gas exchanges and coffee bean quality traits over the canopy vertical profile, in interactions with light and temperature microclimate during the two final stages of berry development. Responses of Coffea arabica L. were observed in the 5th year of a free air CO2 enrichment experiment (FACE) under water-limited rainfed conditions. The light dependent leaf photosynthesis curves (A/PAR) were modelled for leaves sampled from vertical profile divided into four 50-cm thick layers. e[CO2] significantly increased gross photosynthesis (AmaxGross), the apparent quantum yield efficiency, light compensation point, light saturation point (LSP) and dark respiration rate (Rd). As a specific stage response, considering berry ripening, all parameters calculated from A/PAR were insensitive to leaf position over the vertical profile. Lack of a progressive increase in AmaxGross and LSP was observed over the whole canopy profile in both stages, especially in the two lowest layers, indicating leaf plasticity to light. Negative correlation of Rd to leaf temperature (TL) was observed under e[CO2] in both stages. Under e[CO2], stomatal conductance was also negatively correlated with TL, reducing leaf transpiration and Rd even with increasing TL. This indicated coffee leaf acclimation to elevated temperatures under e[CO2] and water restriction. The e[CO2] attenuation occurred under water restriction, especially in A and water use efficiency, in both stages, with the exception of the lowest two layers. Under e[CO2], coffee produced berries in moderate- and high light level layers, with homogeneous distribution among them, contrasted to the heterogeneous distribution under actual CO2. e[CO2] led to increased caffeine content in the highest layer, with reduction of chlorogenic acid and lipids under moderate light and to raised levels of sugar in the shaded low layer. The ability of coffee to respond to e[CO2] under limited soil water was expressed through the integrated individual leaf capacities to use the available light and water, resulting in final plant investments in new reproductive structures in moderate and high light level layers.

Kaolin Film Increases Gas Exchange Parameters of Coffee Seedlings During Transference From Nursery to Full Sunlight

“…The A was fluctuated in two seasons, in well-watered Coffee plantlets, with generally higher assimilation in autumn than in summer as previously observed in Rodrigues et al (2016). The season in adult Coffee plants grown in field conditions without irrigation can produce the opposite effect, showing higher assimilation in rainy summer than in dry autumn (Rakocevic et al, 2021b). Generally, A was higher in C. canephora than in C. arabica in plants protected with KF than in not protected, which was associated with increases in g s .…”

“…The coffee seedlings are produced in nurseries, normally covered with plastic mesh, which can block about 50 to 75% of photosynthetically active radiation (PAR), attaining up to 600-700 µmol m −2 s −1 at midday of one tropical sunny day (Matiello et al, 2010). Under actual air CO 2 concentration, this PAR range is considered as a light saturation point for C. arabica (Rodrigues et al, 2016;Rakocevic et al, 2021b). High light intensities provoke photoinhibition in both C. arabica and C. canephora, decreasing maximum photochemical efficiency (F v /F m ) because of an increased initial and a quenched maximum fluorescence (DaMatta and Maestri, 1997;Martins et al, 2014).…”

Elevated [CO2] Mitigates Drought Effects and Increases Leaf 5-O-Caffeoylquinic Acid and Caffeine Concentrations During the Early Growth of Coffea Arabica Plants

“…In fact, in an early development stage, rapid tissue growth is supported by a high synthesis/degradation of primary metabolites (Aharoni and Galili, 2011). However, the production and accumulation of specialized compounds are also noticed, especially in young leaves and beans from the upper layers, which are more exposed to intense light (Mondolot et al, 2006;Rakocevic et al, 2021). This response seems to be stimulated by e[CO 2 ] exposure and it is species-specific (Sallas et al, 2001(Sallas et al, , 2003Matros et al, 2006;Rakocevic et al, 2021).…”

“…However, the production and accumulation of specialized compounds are also noticed, especially in young leaves and beans from the upper layers, which are more exposed to intense light (Mondolot et al, 2006;Rakocevic et al, 2021). This response seems to be stimulated by e[CO 2 ] exposure and it is species-specific (Sallas et al, 2001(Sallas et al, , 2003Matros et al, 2006;Rakocevic et al, 2021). In needles scots pine seedling, e[CO 2 ] did not affect TPC whereas in needles of Norway spruce seedlings it was reduced by e[CO 2 ] (Sallas et al, 2003).…”

Shaded-Coffee: A Nature-Based Strategy for Coffee Production Under Climate Change? A Review

“…This was associated with a reinforcement of photochemical efficiency, biochemical functioning, and protective mechanisms (Martins et al, 2016;Rodrigues et al, 2016;Scotti-Campos et al, 2019;Avila et al, 2020a,b). Although eCO 2 can alter the content of some compounds in the coffee bean (Marcheafave et al, 2020;Rakocevic et al, 2021), it may also have a positive role in the preservation of bean quality under heat stress (Ramalho et al, 2018). Recent reports show the combined effects of high light and eCO 2 in improving coffee growth and photosynthetic performance (Marçal et al, 2021).…”