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Deciphering of the morpho-physiological traits of two native grasses from Argentina with contrasting drought resistance strategies

Ana Cenzano , Idris Arslan, Ana Furlan, María Varela, Mariana Reginato

Abstract

Context: Semi-arid environments, such as the Patagonian shrublands, are characterized by having shrubby patches surrounded by grasses with different eco-physiological strategies to tolerate long dry periods. Aims: We hypothesized that coexisting grasses of the Patagonian rangeland, already classified as drought-escaping or drought-tolerant, have different traits according to the season and the annual rainfall events. Methods: Two dominant native grasses were selected: Pappostipa speciosa (evergreen) and Poa ligularis (deciduous). Samples were collected in the four seasons for the term of one year. Rainfall events and soil water content of each season were determined. Spring was the wettest season and autumn was the driest season. Physiological (relative water content, pigments, hormones), biochemical (polyphenols, antioxidant activity), and morphological traits were measured in the four seasons. Key results: P. speciosa was characterized by keeping evergreen leaves with high polyphenols production as secondary metabolites with high antioxidant capacity during the dry autumn and winter seasons. P. ligularis was characterized by high gibberellin (GA1), high auxin (IAA), total phenols, total flavonoids, tartaric acid esters contents, and high antioxidant capacity in roots during the autumn dry season. In addition, P. ligularis leaves had higher carotenoids and polyphenols content than P. speciosa during the summer dry season. Conclusions: The major adaptive strategy to tolerate dry periods is the high activity of the secondary metabolism, mainly in leaves in P. speciosa (drought-tolerant grass) and in roots in P. ligularis (drought-escaping grass). Implications: Rainfall variations during a year can affect the phenological growth stages and the metabolism of two native grasses from Argentina characterized by different drought resistance mechanisms.

BT23103  Accepted 04 May 2024

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