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The article presents the results of the study of the petiole anatomy peculiarities of the hybrids between Aigeiros and Tacamahaca sections. Petiole anatomic structure was found to be helpful in assigning taxa to a section and to find intersectional hybrids, which is actual for studying populations in natural and anthropogenic hybridization zones. Cross sections made in the upper part of petioles were used for analyzing anatomic traits by light microscopy. All representatives of the Aigeiros section have linear form of the vascular system, consisting of 3–5 rings, with a rounded contour of the petiole adaxial side. In the Tacamahaca section taxa the vascular system is highly arched, and the adaxial side is cordate. The study of the hybrids between species of the same section revealed that such hybrids inherit anatomy features common for the section. We can consider such traits as adaxial side shape and vascular system type to be the most important markers for intersectional hybrids. Truncated or notched shape of the adaxial contour and vascular system type were found to be characteristic features of hybrids, as small notches in their petioles’ upper part are common for all hybrids. Most of hybrids have small notches, rather than grooves, in the upper part of their petioles. Most of the intersectional hybrids have transitional shape of vascular system. The anatomy of Populus × sibirica petioles confirmed earlier results that it is a hybrid cultivar, that originated as a result of crossbreeding between Aigeiros and Tacamahaca section species.

The article presents the results of the study of the petiole anatomy peculiarities of the hybrids between Aigeiros and Tacamahaca sections. Petiole anatomic structure was found to be helpful in assigning taxa to a section and to find intersectional hybrids, which is actual for studying populations in natural and anthropogenic hybridization zones. Cross sections made in the upper part of petioles were used for analyzing anatomic traits by light microscopy. All representatives of the Aigeiros section have linear form of the vascular system, consisting of 3–5 rings, with a rounded contour of the petiole adaxial side. In the Tacamahaca section taxa the vascular system is highly arched, and the adaxial side is cordate. The study of the hybrids between species of the same section revealed that such hybrids inherit anatomy features common for the section. We can consider such traits as adaxial side shape and vascular system type to be the most important markers for intersectional hybrids. Truncated or notched shape of the adaxial contour and vascular system type were found to be characteristic features of hybrids, as small notches in their petioles’ upper part are common for all hybrids. Most of hybrids have small notches, rather than grooves, in the upper part of their petioles. Most of the intersectional hybrids have transitional shape of vascular system. The anatomy of Populus × sibirica petioles confirmed earlier results that it is a hybrid cultivar, that originated as a result of crossbreeding between Aigeiros and Tacamahaca section species., Представлены результаты изучения петиолярной анатомии видов секций Aigeiros и Tacamahacaи их гибридов. Установлено, что анатомическое строение черешков позволяет диагностировать принадлежность таксона к секции и выявлять межсекционные гибриды; последнее актуально при исследовании зон естественной и антропогенной гибридизации. Листья для работы отбирались со средней части кроны репродуктивно зрелых деревьев с укороченных побегов. Для анализа использовались поперечные срезы, выполненные в верхней части черешка. Материалы исследовались с помощью методов световой микроскопии. Для всех представителей секции Aigeirosхарактерна линейная форма проводящей системы из 3–5 округлых колец и округлый контур адаксиальной стороны черешка. У таксонов секции Tacamahacaона высокоаркообразная, а контур адаксиальной стороны сердцевидный. Изучение гибридов между видами одной секции показало, что они полностью наследуют специфику строения характерную для группы. Наиболее важными анатомическими признаками, маркирующими межсекционные гибриды, следует считать: контур адаксиальной стороны и форму проводящей системы. Характерной особенностью гибридов является усеченный или выемчатый контур адаксиальной стороны черешка, поскольку у большинства из них в верхней части черешка наблюдается не желобок, а только выемка. Форма проводящей системы у большинства межсекционных гибридов промежуточная. Анализ строения черешков Populus× sibiricaподтвердил данные ряда авторов о том, что это гибридный культивар, возникший в результате скрещивания видов секций Aigeiros и Tacamahaca.