ANATOMICAL STRUCTURE OF THE CONDUCTING SYSTEM OF THE POPULUS TREMULA (SALICACEAE) LEAF

A study of the conductive elements arrangement throughout the petiole length and in the midrib of the Populus tremula leaves was carried out. The plants growing wild in Perm and artificially planted in residential areas were studied. It was found that the shape of the petiole cross-section varies throughout its length from broadly heart-shaped (at the distal end) to strongly flattened laterally (at the leaf blade). In the middle part, the petiole is almost rounded. Three groups of collateral conducting bundles enter the petiole, where they regroup to be arranged at 4–5 levels. The additional basal veins of the leaf blade include lateral parts of the groups of bundles of the levels I, II and III. At a distance of about 1 cm from the base of the leaf blade, the leaves of brachyblast have conducting bundles arranged following a linear type. The division of groups of conducting bundles is carried out symmetrically or asymmetrically. The leaves with an asymmetric leaf blade can have both symmetrical and asymmetrical arrangement of conductive elements. There were no significant differences in the anatomical structure of P. tremula petioles between the plants growing in culture and in wild. Stress conditions of the urban environment do not have a fundamental effect on the location of conductive tissues in the petiole throughout its length.