Les légumineuses forestières du genre Acacia en Algérie. Inventaire, description et écophysiologie des espèces végétales du genre Acacia en Algérie. 2022. 128 p. gr8vo. Paper bd.

Abstract

Dryness and salinity act simultaneously in tolerance and acclimatization under saline conditions. Consequently, plants subjected to these types of stress should have developed specific structural adaptations from the germination stage through growth of the root, leaves and stem. The solution to these environmental problems is to look for species that are relatively water-efficient and resistant to recurrent episodes of various abiotic stresses such as salt stress. The effect of the drought was manifested in the distribution of acacia species along the Algerian territory, characterized much more by rainfall. Indeed, the geographical distribution of the genus Acacia Mill. (Fabales Mimosaceae) in Algeria was determined after prospecting, locating and describing populations of different species throughout the Algerian territory. Twenty-four regions were surveyed based on relative abundance of species. According to the climatic data of the years 2000-2016, the following species are adapted to annual rainfall less than 100 mm: A. albida, A. ehrenbergiana, A. laeta, A. nilotica, A. seyal and A. tortilis. Three species (A. karroo, A. farnesiana and A. saligna) are found in areas of annual rainfall between 250 and 500 mm). A. decurrens is located in an area with annual rainfall exceeding 1000 mm. The study of the effect of pretreatments on the ten species identified in Algeria was necessary to improve the regeneration of these species. Thus, the germination rate increases from 5-10% in nature to more than 90% after treatment with sulfuric acid for a definite period. The results also agree that the type of dormancy in seeds of this genus is of a physical type. The objective of the study of the effect of salinity on germination also contributes to determining the threshold of tolerance of the seeds and their regeneration in a saline medium. Only three of the ten listed species will be studied. This selection is based mainly on the geographical distribution and the density of each selected species. A. saligna represents the North, A. tortilis for the South, and A. karroo is a species that is present in the North and in the South at the same time. The classification of the studied species in a descending order of tolerance, on the basis of their germinative capacity, is then the following: A. karroo > A. tortilis > A. saligna. Growth, ionic homeostasis, osmoprotection, salinity tolerance index, as well as anatomical adjustments of A. karroo and

A. saligna grown at various concentrations of NaCl for 21 days were evaluated. The results showed that salt caused remarkable changes in some growth-related parameters, RWC and RWL, photosynthetic pigments, proteins and carbohydrates, depending on the salt level. Na+, Ca2+, and Na+/K+ levels in the leaves increased with salinity levels, while K+ levels were significantly reduced compared to control plants in both acacia species. Levels of proline, total free amino acids and reducing sugars have accumulated considerably in the leaves. Anatomical examinations revealed various anatomical changes in stem and root tissues with regard to saline stress, such as increase / decrease in thickness, cortex, vascular band or spinal cord. A. karroo was more tolerant of salinity than A. saligna. In fact, the values of the tolerance index of plants with salt stress suggest that A. karroo has effectively adopted some mechanisms to acclimate to higher salinity levels. Our results show that the adaptability of a species to salinity is closely related to ion selectivity, osmoprotective accumulation, anatomical adjustments and dry biomass production. Our results confirm that A. karroo and A. saligna are two suitable tree species for soil conservation and ecology, which would promote land reclamation in arid and semi-arid areas.