COIRÓN DULCE (Festuca gracillima Hook, f.) GROWTH PHYSIOLOGY UNDER DIFFERENT DEFOLIATION INTENSITY LEVELS AND WATER RESTRICTION REGIMES

Abstract

Festuca gracillima Hook, f. is a tussock grass species that grows and dominates the rangelands of the Magellan Region in Chile. It may exhibit tolerance to water restriction, while low defoliation intensity could encourage F. gracillima growth regardless of the severity of water deficit. This study aimed to evaluate the effects of defoliation intensity under two water restriction regimes. Two factors were evaluated, defoliation intensity and water restriction regimes. The first factor was defoliation intensity, with four defoliation heights: 3, 5, 8 and 10 cm. The second factor was two levels of water restriction regimes: one emulating typical field conditions of the rangeland, and the other simulating severe water restriction. The experimental design was a randomised complete block design (four defoliation heights × two water restriction regimes × five blocks). The experiment was conducted in a glasshouse, and the data were interpreted using accumulated growing degree days (GDD; base temperature of 0 °C). Defoliation at a height of 10 cm promoted lamina elongation and plant growth under both water restriction regimes, compared to treatments with a greater defoliation intensity. The phyllochron for the species was estimated to range between 262 and 286 GDD across all treatments, increasing up to 504 GDD under severe water restriction at the end of the experimental period. Soil water restriction delayed plant development (i.e., increased the phyllochron) and extended leaf lifespan. Festuca gracillima exhibits a conservative growth strategy (slow traits), which enables it to tolerate high levels of water restriction.