Slow-growing Salix repens (Salicaceae) benefits from changing climate

•Salix repens with slow growth and low resources benefits from changing climate.•Biomass was increased under both elevated temperature and enhanced CO2.•Flavonoids increased under enhanced CO2 and decreased under elevated temperature.•Elevated temperature cancelled out the effect of enhanced CO2 level on flavonoids.•Males had greatest biomass growth and females had higher flavonoid concentrations.

Slow-growing species are thought to be conservative in the response to climate change. Here we studied for the first time the growth and phytochemistry responses to elevated temperature and enhanced CO2 level of the slow-growing Salix repens. Female and male genotypes were exposed to combinations of ambient or elevated temperature (+3.5 °C) and enhanced CO2 level (720 ppm) in greenhouse conditions. Both elevated temperature and enhanced CO2 levels markedly increased the leaf and stem biomass. Elevated temperature reduced the concentration of flavonoids in the leaves, while under enhanced CO2, the concentration increased. The flavonoids quercetin 3-galactoside and quercetin-malonyl-glucoside were the most responsive, and the latter, together with isorhamnetin-malonyl-glucoside, was detected for the first time in a Salix species. In the combined treatment, the effect of the elevated temperature cancelled out the effect of the enhanced CO2 level. Males had the greatest diameter and biomass growth and they had more salicylates in their leaves, while females had higher flavonoid concentrations, but sexes did not differ in their responses to the two climate change factors. The shown plasticity in the biomass growth and leaf flavonoids of the low and slow-growing S. repens, widespread in Northern Europe, proves it able to benefit from the changing climate change in a similar way as its fast-growing Salix relatives.