Root tissue structure is linked to ecological strategies of grasses

The present study investigated to what extent there is a link between root tissue structure and ecological strategies of plant species; such a link is known for leaf tissue structure. We investigated experimentally root tissu e mass density, root diameter and several characteristics of root anatomy i n the axile roots of 19 perennial grass species from different habitats al td related these parameters to the ecological behaviour of the species. Roo t characteristics were assessed ill new roots produced by mature plants gro wn under standardized conditions. The ecological behaviour was characterizc d in terms of relative growth rate (RGR), plant height at maturity and ecol ogical indicator values for nutrients, light and. tolerance to mowing accor ding to Ellenberg. We found a striking dichotomy between root anatomical ch aracteristics associated with interspecific variation ill RGR and those ass ociated with variation in plant height. RGR correlated with anatomical char acteristics that contribute to root robustness, whereas plant height correl ated with characteristics associated with axile root hydraulic conductance. RGR correlated negatively with tissue mass density (TMDr) in roots. Inters pecific variation in TMDr was explained bg the proportion of style in the c ross-sectional area (CSA) of the axile root and the proportion of cell wall in the CSA of the stele. For a given root diameter, slow growing species h ad smaller, albeit more numerous, xylem vessels, indicating a higher resist ance to cavitation and protection against embolisms. Plant height correlate d positively with root CSA, total xylem CSA and mean xylem vessel CSA, indi cating a need for a high transport capacity in roots of species that attain a large size at maturity. TMDr correlated positively with growth matter co ntent in leaves. The results emphasize the dose relationship between tissue structure and growth characteristics at the whole-plant level.