Root microstructural traits regulate ion homeostasis in bush morning glory (Ipomoea carnea Jacq.) for invasiveness success in saline environments.

Invasive plant species are often regarded as ecological pioneers because of their ability to cause substantial economic and environmental impacts when colonizing new habitats. Consequently, predictive frameworks increasingly focus on identifying traits that confer invasiveness and facilitate adaptation to novel environments. The invasion success of many species has been attributed to pronounced phenotypic and anatomical plasticity. In this study, we investigated root structural modifications in Ipomoea carnea to elucidate anatomical mechanisms underlying its invasive success along a salinity gradient ranging from non-saline to hypersaline conditions. Root samples were collected from thirty ecophysiologically distinct sites representing saline and non-saline habitats across Punjab Province and Azad Jammu and Kashmir (AJK), Pakistan. Based on soil salinity of the native habitats, populations were classified into non-saline (ECe < 4 dS m⁻¹), low-saline (ECe 4–8 dS m⁻¹), and highly saline (ECe > 8 dS m⁻¹) categories. Root anatomical analyses revealed pronounced, salinity-dependent structural adjustments. Sodium (Na⁺) accumulation in roots increased markedly under hypersaline conditions (155.49 mg g–1 in plants from the highest saline site), accompanied by significant reductions in root radius (498.3 μm), cortical thickness (187.9 μm), stelar area (0.36 mm2), and the number of metaxylem vessels (15.5 per root). Among these traits, the thinning of the cortical region emerged as a prominent adaptive feature, potentially limiting ion influx and metabolic costs under saline stress. In contrast, increased thickness of sclerenchyma in plants from Namal (78.4 μm) under non-saline habitats and epidermal tissues in plants from Buchal (32.6 μm) under high salinity suggests enhanced mechanical support and barrier functions. Collectively, these coordinated microstructural modifications likely contribute to ion homeostasis and stress tolerance, thereby facilitating the persistence and invasive success of I. carnea in highly saline environments.