Unpredicted, rapid and unintended structural and functional changes occurred during early domestication of Silphium...

Selection for increased yield changed structure, physiology and overall resource-use strategy from conservative towards acquisitive leaves. Alternative criteria can be considered, to increase yield with less potentially negative traits. We compared the morphology, anatomy and physiology of wild and semi-domesticated (SD) accessions of Silphium integrifolium (Asteraceae), in multi-year experiments. We hypothesized that several cycles of selection for seed-yield would result in acquisitive leaves, including changes predicted by the leaf economic spectrum. Early-selection indirectly resulted in leaf structural and functional changes. Leaf anatomy changed, increasing mesophyll conductance and the size of xylem vessels and mesophyll cells increased. Leaves of SD plants were larger, heavier, with lower stomatal conductance, lower internal CO₂ concentration, and lower resin concentration than those of wild types. Despite increased water use efficiency, SD plants transpired 25% more because their increase in leaf area. Unintended and undesired changes in functional plant traits could quickly become fixed during domestication, shortening the lifespan and increasing resource consumption of the crop as well as having consequences in the provision and regulation of ecosystem services.