Photosynthetica 2025, 63(2):151-161 | DOI: 10.32615/ps.2025.008

Synergistic effects of drought and heat stress on Medicago truncatula: understanding growth response and photosynthetic mechanisms

N. RESSAISSI1, 2, W. MNAFGUI1, 3, N. MAIZA1, 2, F. ZRIBI1, W. ZORRIG1, N. LUDIDI3, 4, M.T. SANCHEZ-BALLESTA5, M. BADRI1
1 Laboratory of Extremophile Plants, Centre of Biotechnology of Borj Cedria, P.O. Box 901, 2050 Hammam-Lif, Tunisia
2 Faculty of Sciences of Tunis, University of Tunis El Manar, Campus Universitaire El Manar, 2092 Tunis, Tunisia
3 Plant Stress Tolerance Laboratory, University of Mpumalanga, Private Bag X112831, Mbombela 1200, South Africa
4 DSI-NRF Centre of Excellence in Food Security, University of the Western Cape, Robert Sobukwe Road, 7530 Bellville, South Africa
5 Laboratory of Biotechnology and Postharvest Quality, Institute of Food Science, Technology and Nutrition (ICTAN-CSIC), Jose Antonio Novais 6, 28040 Madrid, Spain

Drought and heat stress significantly threaten forage crop development and photosynthetic activity in the Mediterranean region. This study investigated the physiological responses and photosynthetic activity of two Medicago truncatula lines TN6.18 and F83005.5 (F83), to single and combined heat and drought stress treatments. Biomass traits, leaf gas exchange, and photosystem activities were evaluated. Our findings indicate a reduction in biomass parameters under heat, drought, and combined stress on both lines, particularly in F83. The stomatal conductance and photosynthetic parameters exhibited differential responses, with F83 reducing its stomatal conductance under drought stress, while TN6.18 was adapted by opening its stomata. Moreover, in TN6.18, combined stress enhanced protection mechanisms in PSI, while F83 showed changes in PSII efficiency. These insights deepen our understanding of plant responses to abiotic stresses and offer strategies for improving tolerance and resilience in changing environmental conditions.

Additional key words: combined stress; drought; fodder legume; growth; photosynthetic parameters.

Received: July 11, 2024; Revised: December 22, 2024; Accepted: February 13, 2025; Prepublished online: July 2, 2025; Published: July 10, 2025  Show citation

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RESSAISSI, N., MNAFGUI, W., MAIZA, N., ZRIBI, F., ZORRIG, W., LUDIDI, N., SANCHEZ-BALLESTA, M.T., & BADRI, M. (2025). Synergistic effects of drought and heat stress on Medicago truncatula: understanding growth response and photosynthetic mechanisms. Photosynthetica, 63(2), 151-161. doi: 10.32615/ps.2025.008
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