Growth and Leaf Gas Exchange Upregulation by Elevated [CO] Is Light Dependent in Coffee Plants.

Coffee ( L.) plants have been assorted as highly suitable to growth at elevated [CO] (e), although such suitability is hypothesized to decrease under severe shade. We herein examined how the combination of e and contrasting irradiance affects growth and photosynthetic performance. Coffee plants were grown in open-top chambers under relatively high light (HL) or low light (LL) (9 or 1 mol photons m day, respectively), and a or e (437 or 705 μmol mol, respectively). Most traits were affected by light and CO, and by their interaction. Relative to a, our main findings were (i) a greater stomatal conductance () (only at HL) with decreased diffusive limitations to photosynthesis, (ii) greater during HL-to-LL transitions, whereas was unresponsive to the LL-to-HL transitions irrespective of [CO], (iii) greater leaf nitrogen pools (only at HL) and higher photosynthetic nitrogen-use efficiency irrespective of light, (iv) lack of photosynthetic acclimation, and (v) greater biomass partitioning to roots and earlier branching. In summary, e improved plant growth and photosynthetic performance. Our novel and timely findings suggest that coffee plants are highly suited for a changing climate characterized by a progressive elevation of [CO], especially if the light is nonlimiting.