Adaptive Morpho-Anatomical Characteristics of Leaves and Cones in Juniperus seravschanica Kom.: Studies of Polyphenolic Parenchyma Cells, Secretory Tissues, Sclereids and Tracheids

Abstract

Conifers are long-lived species that cope with multiple abiotic and biotic stresses. To defend themselves, they have evolved a wide array of morphological, anatomical and chemical traits. Morpho-anatomical traits of Juniperus seravschanica, particularly in male and female cones, have not been studied. Thus, in this survey, these structures were studied to investigate the adaptative traits. The species is frost- and drought-tolerant and grows at a 2200-3800 m altitude on normal, chalky, calcareous, rocky, and mountainous outcrops with other species or as pure patches. The seedlings and young plant leaves were small and needle-like, while the main leaves of adult plants were scale-like and overlapping; there was a conspicuous resin gland (duct) in the outer surface of scale-like leaves secreting a white and sticky resinous substance, particularly in damaged leaves. The epidermis was thick with thicker outer walls and sunken stomata; the hypodermis showed 1-3 layers of lignified cells with a narrow lumen. The palisade parenchyma was observed on both sides. Sclereids, phenolic- and starchy cells were observed in leaves, particularly scale-like ones. Male cones were small with overlapping and decussate scales, in which resin glands (ducts) and phenolic cells were also observed. Similarly, female cones had overlapping and decussate scales converting to fleshy, berry-like, and bluish appearance during development. They revealed the presence of several resin glands, a thick epidermis, phenolic cells in young cones, and numerous sclereid cells in mature cones. Tracheids were narrow in leaves and cones. The features such as high sclerophylly, resin glands, phenolic cells, narrow tracheids, sunken stomata, increasing thickness of the epidermis, cuticle, hypodermis, as well as the presence of palisade parenchyma on both sides enable the species to survive in hard conditions.