Ecological adaptations of Justicia adhatoda L. against environmental constraints: Strategies for survival and sustainability

Sixteen ecologically distinct ecotypes of Justicia adhatoda (L.) Pers. were studied to explore key attributes of its widespread distribution in heterogeneous environments. Ecotypes of saline areas (KW, KL and KK) showed better vegetative growth (shoot fresh and dry weight and plant height) and accumulation of inorganic ions sodium (Na+), potassium (K+) and calcium (Ca2+) as compared to all other ecotypes. Increased stem radii, scarification around parenchyma (pith and cortex) and increased metaxylem area were remarkable modifications to resist environmental changes. Notable stem modifications in dry mountains included the development of thicker collenchyma tissue and reduced protoxylem and vessel number. Moreover, longer shoots and increased shoot potassium in the KM population help to improve water conservation by reducing surface water loss and increasing storage capacity. Ecotypes from Mountain Valley exhibited the most distinct characteristics in growth, physiology and anatomy features, less shoot K+ and Ca2+ contents, and increased epidermal cell, cortical region and protoxylem cell area. The populations along the roadside (CS, BU, MN and FD) had specific anatomical variations like epidermal thickening and intensive sclerification around cortical regions. It was concluded that different populations of Justicia adhatoda L. exhibited variations in morpho-physiology and anatomy in heterogeneous environments that may contribute to its distribution and diversification.