Photosynthetica 2025,63(4):346-357 | DOI: 10.32615/ps.2025.034

Unravelling the differential responses of critically endangered Onobrychis conferta populations to drought and salinity stress

A. SAKHRAOUI1, 2, 3, H.B. LTAEIF2, J.M. CASTILLO3, S. ROUZ2
1 Higher School of Agriculture of Kef, University of Jendouba, 7119 Le Kef, Tunisia
2 Department of Agricultural Production - Laboratory of Agricultural Production Systems and Sustainable Development (SPADD), LR03AGR02, Higher School of Agriculture of Mograne, Carthage University, 1121 Mograne, Zaghouan, Tunisia
3 Department of Plant Biology and Ecology, University of Seville, Apartado 1095, 41080 Sevilla, Spain

Understanding stress responses of endangered plants is vital for their conservation under climate change. We examined the effects of iso-osmotic drought (PEG) and salinity (NaCl) on the growth and physiology of three populations of the critically endangered legume Onobrychis conferta subsp. conferta (OC1, OC2, OC3) endemic to North-Western Tunisia. Both stresses reduced photosynthesis, stomatal conductance, intercellular CO2, and carboxylation efficiency, while increasing intrinsic water-use efficiency. PSII photoinhibition (Fv/Fm decline) occurred after 6 d. Prolonged stress suppressed growth and water content, particularly under salinity, but enhanced root elongation and root-to-shoot ratios in OC1 and OC2. OC3, from dry grasslands, showed higher water retention, photosynthetic efficiency, and adaptive morphology than OC1 (Pinus forest) and OC2 (watercourse edge), highlighting ecotype-dependent tolerance. OC1 exhibited increased root allocation under salinity, exhibiting a salt-avoidance strategy. Identifying resilient ecotypes is crucial for conservation, restoration, and adaptation of O. conferta to increasing drought and salinity.

Additional key words: chlorophyll; fluorescence; gas exchange; iso-osmotic stress; NaCl; sainfoin.

Received: August 27, 2025; Revised: November 7, 2025; Accepted: November 11, 2025; Prepublished online: December 16, 2025; Published: December 31, 2025  Show citation

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SAKHRAOUI, A., LTAEIF, H.B., CASTILLO, J.M., & ROUZ, S. (2025). Unravelling the differential responses of critically endangered Onobrychis conferta populations to drought and salinity stress. Photosynthetica, 63(4), 346-357. doi: 10.32615/ps.2025.034
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