Microstructural Features of Primula woronowii Losinsk., Primula macrocalyx Bunge. and Primula saguramica Gavr. from Georgian Flora

Abstract

DOI: 10.52340/GBMN.2023.01.01.17 Background: The characterization and study of plants begin with the study of morphological and micro-diagnostic signs. It is essential to determine the common and distinguishing features of the species of the genus Primula to facilitate their identification. Objectives: The paper presents the macro- and micromorphological characteristics of three species of the genus Primula L.: P. woronowii Losinsk., P. macrocalyx Bunge, and P. saguramica Gavr. In addition, based on the microstructural and anatomical characteristics, the paper distinguishes between two closely related species: P. macrocalyx Bunge and P. saguramica Gavr. Methods: Microstructural research on experimental samples was carried out using standard laboratory methods adopted in microtechnology. The microtechnical investigation used light microscopes (Carl Zeiss, Jeneval, and Omax). Materials were documented using a digital camera (Canon Digital IXUS 75), and microphotographs were graphically processed in the Adobe Photoshop CS5 program. Results: Based on the data, the following common and distinguishing microstructural features of P. woronowii, P. macrocalyx, and P. saguramica were established: The basal cells of the epidermis of the leaf of the studied species are non-circular, with a curved and curved-walled structure; The ventilation system is simple, a normocytic structure; the leaf is bifacial Dorsoventra luri, amphistomatous (P. woronowii, P. saguramica), and hypostomatic (P. macrocalyx); Conductive tissue both in the leaf and the aboveground axis organs has an open, collateral, vascular fiber structure; P. macrocalyx and P. saguramica, which are closely related by macro- and micromorphological characteristics, can be separated by the anatomical structure of the mesopetiole zone of the leaf stalk and the structural elements of the wood in the central cylinder of the root. Conclusions: Common and distinguishing features of all three species were identified: The basal cells of the upper and lower epidermis of the leaves of P. woronowii, P. macrocalyx, and P. saguramica are non-stitched, curvilinear, and curved-walled; also, a chaotically arranged stomata apparatus differentiated into a simple, anomocytic type is typical for all three species, and the presence of a cystolith in the cells of the upper epidermis of P. woronowii leaf is observed. In all three species of petiole xylem, there are large, oval-shaped openings surrounded by mechanical-type cells. Small-caliber spaces in P. woronowii and P. saguramica are arranged longitudinally, while in P. macrocalyx, they are arranged asymmetrically with differentiated spherical lumens. The cross-section of the axial organs of the flower is oval or spherical in outline; the flower stem, but not the stalk, is characterized by the obliteration of medullary cells; P. saguramica collenchyma is of a mixed type, while P. woronowii and P. macrocalyx have lamellar collenchyma. Endodermal cells of P. saguramica have clearly expressed Casparian strips, but in the P. woronowii and P. macrocalyx endoderm, they are less apparent; the central cylinder of P. woronowii and P. macrocalyx is pentarcular, while P. saguramica tends to have a multi-beam xylem structure. In all species, the cells of the central tissue of the crown petals are exceptionally thin-walled, isocytic, and surrounded by dense epidermal tissue; their transitional tissue is incomplete; only the lumens of the conducting vessels of the xylem are visible.