Effect of water deficit on Argan tree seedlings (Argania spinosa L. Skeels): Morphological and physiological aspect

The Argan tree, Argania spinosa L., Skeels, is an endemic species in North-West Africa perfectly adapted to aridity and drought. It is in this context that we studied the physiological impact of water deficit on the Argan tree seedlings for eight weeks at a field capacity of 30%. The obtained results reveal that the stressed seedlings manifested by the strategy of the root elongation from the second week, the roots reached 31 cm compared with 15 cm of the control. However, the seedlings showed severe dehydration of 41% in leaves and 45% in roots. Besides, the content of chlorophyll pigments has relatively decreased from the second week, a slight yellowing and leaf drop was observed. The seedlings have accumulated proteins in a very significant way in leaves (from 25 to 107 mg.g-1 by fresh weight) and (from 23 to 90 mg.g-1 by fresh weight) in roots. Proline was also accumulated; the content was 4 and 2 μg.g-1 by fresh weight respectively in leaves and roots compared with 1.3 and 1.1 μg.g-1 1 by fresh weight in control respectively. The accumulation of the protein and proline is higher in leaves than in roots. The content of malondialdehyde was higher in leaves than in roots. This increase is significantly related to the prolongation of the stress period from the second week. The enzymatic activity of peroxidase is in relative increase according to the duration of the water stress applied in both leaves and roots. We deduce from these results that Argan seedlings possess the characteristic of xeropyhte that tolerate aridity. Key words: Argania spinosa, drought stress, proline, chlorophylls, proteins