Adaptive morpho-anatomical characteristics of the critically endangered plant Myricaria laxiflora in the Yangtze River Basin, China

Myricaria laxiflora, a National Class II critically endangered plant once declared extinct in the wild, is the only species in the genus Myricaria that occurs outside plateau regions and remains evergreen during winter. It serves not only as an ideal species for riparian zone restoration and soil conservation but also as a key model for studying genetic variation and ecological adaptation in plants. This species survives under alternating flood and drought conditions, exhibiting specialized anatomical traits in its roots, stems, and leaves. Using freezing microtome techniques, we investigated the anatomical adaptations of its roots, stems, leaves, and seeds to alternating flood and drought environments. The results showed that the roots develop a thickened periderm and large-diameter vessels, significantly enhancing water transport and stress resistance. The stems contain densely arranged phloem and xylem fibers, which enhance both mechanical strength and nutrient conduction efficiency. The leaves exhibit typical xeromorphic characteristics, including bifacial palisade tissues, a thick cuticle, and sunken stomata, which enable adaptation to intense light and drought stress. The seeds are small and lightweight, possessing hydrophobic lipid coatings and awn structures that facilitate efficient wind-and water-mediated dispersal. These integrated anatomical adaptations collectively enable M. laxiflora to thrive in the extreme riparian environments of the Yangtze River Basin, providing crucial theoretical foundations for its conservation and ecological restoration.