A bitter future for coffee production? Physiological traits associated with yield reveal high vulnerability to hydraulic failure in Coffea canephora

Abstract

The increase in frequency and intensity of drought events have hampered coffee production in the already threatened Amazon region, yet little is known about key aspects underlying the variability in yield potential across genotypes, nor to what extent higher productivity is linked to reduced drought tolerance. Here we explored how variations in morphoanatomical and physiological leaf traits can explain differences in yield and vulnerability to embolism in 11 Coffea canephora genotypes cultivated in the Western Amazon. The remarkable variation in coffee yield across genotypes was tightly related to differences in their carbon assimilation and water transport capacities, revealing a diffusive limitation to photosynthesis linked by hydraulic constraints. Although a clear trade‐off between water transport efficiency and safety was not detected, all the studied genotypes operated in a narrow and/or negative hydraulic safety margin, suggesting a high vulnerability to leaf hydraulic failure (HF), especially on the most productive genotypes. Modelling exercises revealed that variations in HF across genotypes were mainly associated with differences in leaf water vapour leakage when stomata are closed, reflecting contrasting growth strategies. Overall, our results provide a new perspective on the challenges of sustaining coffee production in the Amazon region under a drier and warmer climate.

Evidence of combined flower thermal and drought vulnerabilities portends reproductive failure under hotter‐drought conditions

“…A possible explanation for these unexpected results may involve the different sources of water leaks integrated by the residual conductance (Duursma et al, 2019; Machado et al, 2020), and their differential contribution to g flower and g leaf‐res . A growing body of evidence shows that, in addition to the cuticle, significant amounts of water vapor can “escape” through stomatal pores ( g stomata ), even after complete stomatal closure, in such a way that species with higher stomatal density (SD) tend to have higher g leaf‐res (Loram‐Lourenço et al, 2022; Machado et al, 2020; Max et al, 2023). Thus, given that leaves allocate a much higher fraction of their epidermis to stomata (An et al, 2023; Lipayeva, 1989; Zhang et al, 2018), and considering the thinner cuticle wax coverage of flowers (Cheng et al, 2021), it is possible that the lack of significant differences between g flower and g leaf in the studied species does not necessarily imply that flower cuticle can be as effective as that on leaves in avoiding water leaks, it can indicate that g stomata on leaves can be higher than on flowers.…”

“…A possible explanation for these unexpected results may involve the different sources of water leaks integrated by the residual conductance (Duursma et al, 2019;Machado et al, 2020), and their differential contribution to g flower and g leaf-res . A growing body of evidence shows that, in addition to the cuticle, significant amounts of water vapor can "escape" through stomatal pores (g stomata ), even after complete stomatal closure, in such a way that species with higher stomatal density (SD) tend to have higher g leaf-res (Loram-Lourenço et al, 2022;Machado et al, 2020;Max et al, 2023).…”