Abstract
Increasing atmospheric [CO2] is thought to contribute to changes in precipitation patterns, increasing heatwaves and severe drought scenarios. However, how the combination of elevated [CO2] and progressive drought affect plant metabolism is poorly understood. Aiming to investigate the effects of this environmental condition on photosynthesis and specialized metabolites in leaves ofCoffea arabicaduring the early growth, plants fertilized with ambient (a[CO2]-400 ppm) and elevated (e[CO2]-800 ppm) [CO2] were exposed to well-watered (WW) or water-deficit (WD) regimes for 40 days. Over the 40-day-water-withdrawal, soil moisture, and leaf water potential decreased compared to WW-condition. Elevated [CO2] stimulates CO2assimilation (A) and intrinsic water use efficiency (iWUE) even under WD. Drought condition slightly changed stomatal conductance, transpiration rate and maximum quantum efficiency of photosystem II (PSII) regardless of [CO2] compared to WW-plants. Total soluble amino acid concentration did not change significantly, while total phenolic compounds concentration decreased under e[CO2] regardless of water regimes. The combination of e[CO2]+WD increased the 5-O-caffeoylquinic acid (5-CQA) and caffeine amounts by 40-day when compared to a[CO2]+WD plants. Altogether, these results suggest that e[CO2] buffers mild-drought stress in youngC. arabicaby increasing A, iWUE and stimulating changes in the leaf contents of 5-CQA and caffeine.
Highlights
The concentration of carbon dioxide ([CO2]) in the atmosphere is one of the environmental factors of the greatest influence on plant development
On day 0 (i.e., 30 days after e[CO2] acclimation and before water restriction), CO2 assimilation and intrinsic water use efficiency increased 3- and 3.9-fold, respectively, and remained higher in WW condition relative to a[CO2] plants (Figures 2A,D). Water deficit reduced these parameters in e[CO2]+WD plants on day 20 and 40 after the stress onset, relative to e[CO2]+WW, but they were still higher than a[CO2]+WD, especially on day 20 (Figures 2A,D)
We assessed whether elevated [CO2] will ameliorate drought stress and how the combination of these environmental conditions will affect the metabolism of specialized metabolites in young C. arabica plants
Summary
The concentration of carbon dioxide ([CO2]) in the atmosphere is one of the environmental factors of the greatest influence on plant development. The increase in atmospheric [CO2] contributes to the greenhouse effect and changes in the precipitation pattern, which could favor flood and more frequent drought. The initial effects of drought on plants are related to stomatal closure, decrease in leaf area, acceleration of leaf senescence and abscission aiming to control water status. These responses reduce the availability of CO2 in the chloroplasts inhibiting photosynthesis and modifying carbohydrate supply for metabolism (McDowell et al, 2008). As drought severity increase biochemical restrictions and oxidative stress impair plant development, which can later cause plant death (Seleiman et al, 2021)
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