Wood density, but not leaf hydraulic architecture, is associated with drought tolerance in clones of Coffea canephora

Abstract

Robusta coffee (Coffea canephora) is largely cropped in regions where drought stress is the major bottleneck limiting crop yields. We hypothesized that clonal differences in wood density (D w) would be reflected in xylem anatomical differences with associated consequences for hydraulic functioning and ultimately drought tolerance. We assessed the major functional properties of water conduction systems at both the leaf and stem levels in 8-year-old clones of robusta coffee with varying degrees of drought tolerance. The plants were grown outdoors in 24-L pots and either irrigated or subjected to a 4-month water deficit. Upon drought imposition, increased D w, primarily associated with a rearrangement of the fiber matrix and secondarily associated with narrower vessels (although more numerous per cross-sectional area), was correlated with tolerance to hydraulic dysfunctions. Some coordination at the leaf level concerning hydraulic and stomatal anatomical patterns, with stem structural properties, was observed under ample irrigation, but this coordination was decoupled by the imposed drought stress. In conclusion, our data suggest a role for D w in drought tolerance in coffee; however, drought tolerance implies that clones that successfully thrive under low water supply might have compromised fitness under ample irrigation, suggesting a trade-off between D w and the conduction capacity in coffee.