Caracterización de yemas de Festuca arundinacea y Lolium perenne bajo diferentes niveles de estrés hídrico en verano y otoño en un ambiente limitante para el crecimiento

Winter perennial grasses play a key role in Uruguayan pasture systems due to their contribution to productive sustainability, with regeneration from axillary buds being a central component of their persistence under water stress. This study evaluated the number and physiological state of buds in tall fescue (Festuca arundinacea) and perennial ryegrass (Lolium perenne) under different levels of water deficit during the summer and autumn of 2024–2025 in the northern coastal region of the country.

A field experiment was conducted at the Experimental Station of the Faculty of Agronomy (Salto), with treatments of irrigation and moderate and severe water deficit. The total number of buds per tiller was quantified, and their physiological state (active, dormant, and dead) was determined using tetrazolium and Evans Blue staining techniques. To analyze the collected data, general linear and generalized linear mixed models were fitted with environmental covariates associated with water and heat stress, and ANOVA tests and mean comparison tests were implemented.

The results showed that the total number and physiological state of the buds were determined by the interaction between species, season, water treatment, and time of evaluation. Tall fescue (Festuca arundinacea) presented a more abundant and stable bud bank, especially during autumn, while perennial ryegrass (Lolium perenne) showed greater sensitivity to summer stress, evidenced mainly by an increase in the proportion of dormant buds. Water deficit was primarily associated with increased dormancy, while supraoptimal temperatures favored bud activation, without marked increases in mortality.

The study concludes that the persistence of these perennial grasses in environments with water deficit and heat stress depends more on their ability to regulate the physiological state of their bud bank than on its size. Tall fescue (Festuca arundinacea) exhibits intrinsic morphophysiological strategies that confer greater stability and recovery capacity under stress, while perennial ryegrass (Lolium perenne) shows less persistence under these conditions. These results confirm the hypotheses and highlight the bud bank as a key indicator for the management and selection of forage species in pasture systems subjected to restrictive climatic conditions.