Phenological, morphological, and anatomical adaptive strategies of Retama raetam (Fabaceae) in Saharan and steppe environments

Saharan and steppe ecosystems host a distinctive flora adapted to severe environmental conditions. One representative species is Retama raetam (Forssk.) Webb & Berthel., a xerophytic shrub in the Fabaceae family, recognized for its ecological importance and pastoral and medicinal value. The objective of this research was to examine the morpho-phenological characteristics and anatomical features of Retama raetam populations growing in Saharan and steppe habitats. To achieve representative coverage, subjective sampling was combined with the minimum-area method. Six morphological parameters were assessed: plant height, circumference, number of leaves per plant, leaf length, flower length, and fruit length. In addition, four phenological stages (leaf emergence, flowering, fruiting, and fruit maturation) were monitored over time. Histological analyses focused on stem and leaf cross-sections, while anatomical measurements included epidermal thickness, cortical parenchyma cell diameter, xylem vessel diameter, and the dimensions of piliferous crypts. The statistical analysis of the results indicated a general morphological similarity between plants from the two regions. Nevertheless, phenological observations showed that plants from Saharan locations entered developmental stages earlier than those from steppe environments, a pattern likely linked to climatic and environmental differences. Anatomical investigations confirmed that Retama raetam exhibits structural traits associated with xerophytic adaptation in both habitats. Significant histological differences were recorded between sites, particularly in epidermis thickness (P = 0.00013), cortical parenchyma diameter (P = 0.0078), and crypt width (P = 0.0016). These findings demonstrate that Retama raetam is highly adapted to both Saharan and steppe conditions.