PJB-2026-51
Short-term irrigation dismantles integrated phenolic-osmolyte defenses in drought-acclimated Pistacia atlantica Desf.
Fethi TOUL: https://orcid.org/0000-0002-5291-3026
Abstract
Pistacia atlantica Desf. is a key drought-tolerant tree in hyper-arid North African ecosystems, yet little is known about how its osmolytes and phenolic-based antioxidant system respond when water availability is transiently improved. This study evaluated the short-term effects of irrigation on osmolyte levels, phenolic composition, and antioxidant activity in drought-acclimated P. atlantica trees.
Ten adult trees in the hyper-arid Igli region (southwestern Algeria) were assigned to non-irrigated and irrigated groups (5 trees each). Irrigated trees received water twice weekly for 90 days; controls remained under natural drought. Leaves were sampled before irrigation (T0) and after 90 days. Relative water content, proline, glycine betaine, total phenolics, and individual phenolics (HPLC-DAD) were determined and analysed by one-way ANOVA and Pearson correlation.
In non-irrigated trees, leaf water content, proline, glycine betaine, total phenolics, and DPPH IC50 did not differ between T0 and 90 days, indicating a stable drought-acclimated state. In contrast, irrigation increased leaf water content by about 12% and significantly reduced proline (−25%), glycine betaine (−22%), and total phenolics (−30%), while IC50 increased by 25%, reflecting weaker antioxidant capacity. All quantified phenolics decreased after irrigation; the largest reductions (−24 to −27%) were observed for chlorogenic, ferulic and p-coumaric acids and quercetin, whereas gallic, syringic, ellagic acids and naringenin showed smaller declines (−8 to −16%). Proline, glycine betaine, total phenolics, and major phenolics were strongly and positively correlated, whereas antioxidant activity showed an inverse relationship with this cluster.
Short-term irrigation of drought-acclimated P. atlantica rapidly down-regulates osmolyte accumulation and phenolic-based antioxidant defences. The close coupling between osmolytes, key hydroxycinnamic acids and flavonols, and antioxidant activity indicates an integrated defence network that is highly sensitive to water availability and central to drought resistance and recovery in this species.
Key words: Pistacia atlantica, drought stress, biochemical markers, osmolytes, phenolic compounds.
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