Delineating drought-induced antioxidative traits as potential mechanisms for climate resilience in Argania spinosa

Abstract

Drought stress ranks among the most critical environmental challenges facing agriculture today, causing significant impairments to plant growth and development. In Morocco, these negative impacts are projected to intensify further under the combined pressures of climate change and the worsening water shortage crisis. The imperative need for sustainable arganiculture (cultivation of Argane trees) in dry lands necessitates the expeditious identification of drought-tolerant elite Argania spinosa trees. In this context, we investigated the drought tolerance of 2-year-old A. spinosa seedlings from two contrasting provenances Lakhssas (LKS) and Aoulouz (ALZ) under severe stress by evaluating their antioxidative defense mechanisms. A total of 24 parameters related to reactive oxygen species (ROS), oxidative damage, and enzymatic and non-enzymatic antioxidant defense were measured and compared between both provenances. The results showed that the drought-stressed conditions significantly increased the activity of enzymatic antioxidants, including superoxide dismutase, catalase, peroxidase, polyphenoloxidase, glutathione peroxidase, glutathione S-transferase, and ascorbate-glutathione cycle enzymes, as well as the content of non-enzymatic antioxidants, including reduced glutathione (GSH), ascorbic acid (AsA), α-Tocopherols (α-toc), polyphenols, anthocyanins, and group thiols. The ability of A. spinosa trees to greatly enhance their antioxidant system to limit cellular damage caused by ROS production might be an important attribute linked to drought tolerance. Regarding the inter-provenance variation under drought stress conditions, LKS provenance exhibited superior antioxidative capacity through enhanced AsA-GSH cycle activity and elevated levels of AsA-GSH, α-toc, and polyphenols. However, ALZ demonstrated elevated anthocyanin levels and reduced peroxidative stress markers (hydrogen peroxide and malonyldialdehyde). Significant and positive correlations were recorded between studied ROS and antioxidants. Investigating the multifaceted antioxidative defense system underpinning drought tolerance in A. spinosa can facilitate the identification of drought-tolerant argane trees for the development of a future breeding program allowing sustainable arganiculture in dry lands.