Cambios morfo-fisiológicos en Festuca arundinacea y Dactylis glomerata, creciendo bajo sotobosque

The experiment was conducted on a private property located 18.5 km from Fraile Muerto, Cerro Largo Department, Uruguay, during the spring of 2019.

The effect of trees on the physiology, morphogenesis, and structure of Dactylis glomerata and Festuca arundinacea was evaluated. Measurements were taken in single tree rows oriented north–south, with a 19 m spacing between rows, and in three perpendicular positions relative to the tree row: position I (center of the alley), position M (intermediate between tree row and center of the alley), and position Ar (near the tree row), plus an open-field control (C). The tree component consisted of 12-year-old clones of the hybrid Eucalyptus grandis × Eucalyptus camaldulensis. The experimental design was a randomized complete block design (RCBD) with split plots and three replicates within each plot. The total experimental area covered 0.3 hectares.

Regarding the morphological variables evaluated, the position relative to the trees had no effect on phyllochron, leaf appearance rate (LAR), or leaf expansion rate (LER) for either species. However, the number of live leaves per tiller (NLL) was significantly higher in position Ar compared to the control, with values of 4.61 and 3.44, respectively. A significant difference was also found between species in overall NLL, with 3.6 for Festuca arundinacea and 6.2 for Dactylis glomerata. For mean leaf length (MLL), statistically significant differences were found between shaded treatments and the control, with longer leaves observed in shaded conditions. No significant differences were found in leaf senescence rate (SR) between treatments or between treatments and the control. When comparing species, SR was 0.22 for F. arundinacea and 0.35 for D. glomerata, a statistically significant difference.

From the analysis of ETR vs. PAR response curves, no statistically significant differences were found in ETRmax, Fv/Fm, or IK between F. arundinacea and D. glomerata. However, a significant difference (p = 0.05) was found for α (slope of the rapid rise of the curve), indicating that D. glomerata has greater quantum efficiency than F. arundinacea. No statistically significant differences were found between positions in the alley.

The results of this study confirm that the presence of trees causes changes in morphology and physiology in the studied species. Quantum efficiency under trees is enhanced, as are the structural variables NLL per tiller and MLL, as a result of shading. The increase in NLL per tiller can be explained by lower senescence rates, and the increase in MLL as a shade acclimation response.