Should I GROW or should I SLOW: A meta-analysis of fast-growing tree-species grown in cadmium perturbed environment.

Variations in soil chemical composition may lead to disturbances in plant growth and survival. Which strategies of biomass allocation fast-growing species acquire to overcome the disturbances in the rhizosphere remains an open research challenge. We conducted a series of greenhouse pot experiments to collect enough experimental evidence to elucidate the answer. A tiered analytical approach was applied to collected data to fingerprint both the intraspecies and interspecies differences. We investigated the biomass allocation patterns in Robinia pseudoacacia L., Populus × euramericana, Populus deltoides, Salix alba, Salix matsudana Koidz., and Salix viminalis L. (18 fast-growing genotypes in total) under cadmium-free and cadmium-perturbed soil conditions. Further, we explored the intraspecific and interspecific differences between tested plants and looked for different strategies employed under perturbed conditions. We show that fast-growing species tend to strengthen their roots toward the Cd triggered perturbances in the rhizosphere and allocate more biomass to that plant organ/part. Intraspecies analyses pointed to differences in resource use efficiency and acquisition strategy based on specific leaf area, pointing toward P. deltoides genotypes PE19/66 and PD3, and S. alba B44 as strong, fast-growing oriented genotypes. Others exhibited more or less a conservative resource use and acquisition strategy under perturbed conditions. Our study highlights the intraspecies and interspecies specificity of fast-growing species to Cd occurrence in the rhizosphere. Association of growth traits and Cd-related traits tested with structural equation model highlighted the shoots bioconcentration index as a proxy-trait which directly interplay with the functional traits performance and modify the biomass shift.