Characterization of Medicago arborea L. Response to Water and Salt Stress

Medicago arborea L. is a Mediterranean leguminous fodder shrub, regarded as a promising species in arid and semi-arid lands where it can play an important role in the elaboration of a durable pastoral system. The aim of this paper is to investigate and characterize the response of M. arborea plants to water and salt stress at the early growth stage. Seedlings of the species derived from seeds collected in the Djelfa province, Algeria, were grown in pots under greenhouse conditions and separately submitted to water stress, restoring 20%,40%,60%,80% and 100% of substrate field capacity, and salt stress, supplying irrigation water with 0, 50, 100, 150 and 200 meql-1 of NaCl+CaCl2. Stress effects were determined on fresh and dry-matter biomass, relative water content, leaf pigment content (chlorophyll and carotenoids), proline and total soluble sugars amount. Results showed that both water and salt stress affected seedlings growth. In particular, the lowest water regime (20% of field capacity) significantly reduced fresh and dry-biomass and relative water content, whereas seedlings under salinity maintained a good water content (>70%).Chlorophyll a and b, and carotenoids content did not show significant differences among treatments, while proline and total soluble sugars amounts, major osmolytes involved in osmotic adjustment, significantly increased according to salt and water stress intensity. The findings highlight that M. arborea has a remarkable potential of tolerance to water deficit and salinity, involving a range of physiological strategies to cope with stress by regulating metabolism activity and maintaining cell turgor.