Structural and Reproductive Adaptations in the Endemic Silene zawadskii in Response to Alpine Environmental Stress

Silene zawadskii Herbich is an endemic species restricted to the South-Eastern Carpathians, being found in Romania and Ukraine. The species is rare and protected in the two countries. The root system is deep, to facilitate water absorption, the basal leaves, arranged in a rosette, are leathery and glabrous. The stem presents numerous multicellular, uniseriate non-glandular trichomes, only in the upper part; they become caducous at the base. The small size of the plant, correlated with the very narrow xylem vessels, represents a way of increasing the resistance to physiological drought and preventing embolism in drier periods. Another particular feature of this species is the presence of numerous large calcium oxalate crystals (druses), both in the stem and especially in the leaves. The flowers are adapted to entomophilous pollination, showing structural traits that facilitate interactions with alpine pollinators, particularly under conditions of reduced insect diversity at high altitudes. These anatomical traits reflect its ecological specialization, making it a valuable indicator for assessing edaphic–climatic niche specificity and the functional connectivity of high-altitude ecological networks.