Adaptive responses of Limoniastrum monopetalum (L.) Boiss. growing naturally at different habitats

Abstract

Limoniastrum monopetalum is a perennial halophyte growing at different habitats along the Mediterranean Sea coast of Egypt. The morpho-anatomical and physiological responses was investigated for L. monopetalum leaves collected from; wet salt marshes, coastal sand dunes and rocky ridges habitats. The plant acquired the highest values of leaf area, lamina thickness, specific leaf area and water content despite of the high salinity in the salt marshes habitat. Additionally, plant is able to regulate content of Na+, Cl−, K+, Ca2+, Mg2+, accumulate proline and total phenols. On the other hand, plants growing in the driest habitats (coastal sand dunes and rocky ridges) acquired xeromorphic features viz., thick cuticle, compacted palisade tissue, increasing lignification of sclerified tissue and ash content. Moreover, plants in coastal sand dunes displayed extra adaptive responses viz., increase in chl. a, chl. b, carotenoids, K+ and Cl−, palisade ratio and stomatal densities. Plants growing at rocky ridges were affected by drought and salinity together. Those acquired the highest Na+ and Na+/K+, associated with the lowest in osmotic potential. In general, L. monopetalum able to exclude salt outside cells via salt glands scattered on leaf surfaces. These mechanisms permit L. monopetalum to tolerate and survive under stressful coastal habitats of Egypt.