Root and Shoot Trait Adaptations During Vegetative Development of Festuca gracillima Ecotypes from Two Xeric Patagonian Vegetation Types Under Controlled Conditions

Perennial plant ecotypes exhibit adaptive functional traits associated with abiotic stress tolerance linked to their origin. This study hypothesized that F. gracillima displays ecotypic variation that employs different shoot–root compensation mechanisms to sustain plant growth and development. A growth chamber experiment was conducted to investigate the adaptive traits of F. gracillima accessions derived from seeds collected in steppe and transition zones. Destructive sampling was performed at six development stages, while non-destructive measurements were taken biweekly (roots) and every 2 days (shoots) from six pots per accession. The development stages were (i) seedling, (ii) one fully expanded leaf, (iii) two fully expanded leaves, (iv) three fully expanded leaves, (v) early senescence, and (vi) late senescence (one fully senesced leaf). A factorial design with six developmental stages × two accessions × six replicates was used. The steppe accession had a greater fine-root length percentage, a smaller root diameter, longer single roots, fewer roots, a slower rhizochron (i.e., a slower root appearance rate) and a faster leaf phyllochron (i.e., a faster leaf appearance rate). Phenotypic differences between accessions support the existence of ecotypic variation. The steppe accession combined acquisitive and conservative traits, indicating multidimensional trait variation rather than a single acquisitive–conservative strategy. Additionally, asynchronous leaf and root tissue appearance rates suggest partial decoupling between above- and belowground development.