A comparative anatomical and taxonomic study of three aquatic species: Typha domingensis, Eichhornia crassipes, and Nasturtium officinale

This study was conducted at three stations along the Tigris River in Salah al-Din Governorate (Al-Dhuluiya, Al-Alam, and Baiji) to compare the leaves of three aquatic and semi-aquatic species Typha domingensis, Eichhornia crassipes, and Nasturtium officinale from both morphological and anatomical perspectives. The anatomical examination of transverse leaf sections revealed distinct structural variations reflecting ecological adaptations. Eichhornia crassipes exhibited the most extensive development of aerenchyma, with large intercellular air spaces occupying the majority of the mesophyll, a clear adaptation to its free-floating aquatic lifestyle. Typha domingensis showed well-developed but comparatively smaller aerenchyma, consistent with its emergent growth in swampy habitats. Nasturtium officinale, in contrast, possessed a mesophyll with moderately developed intercellular spaces and limited aerenchyma, corresponding to its semi-aquatic habitat. Morphological observations further supported these adaptations. Typha domingensis bears long, linear, ribbon-like leaves (1–3 m in length) with parallel venation, providing mechanical support and efficient emergent growth. Eichhornia crassipes is characterized by broad, ovate to orbicular floating leaves with inflated, spongy petioles that enhance buoyancy. Nasturtium officinale has pinnately compound leaves with fleshy, ovate leaflets and long, flexible petioles, adaptations that facilitate survival in partially submerged and humid environments.