Morphological features of the leaves in clematises as a reflection of their ecological peculiarities

Quantitative morpho-anatomical features of leaves of nine Clematis taxa (C. alpina ‘Pamela Jackman’, C. macropetala ‘Maidwell Hall’, C. integrifolia ‘Aljonushka’, C. ispahanica ‘Zvezdograd’, C. fargesii ‘Paul Farges’, C. texensis ‘Princess Diana’, C. tibetana, C. viticella, and C. heracleifolia) were determined with the aim to analyze their adaptation to the environmental conditions. Among investigated clematises, there were plants with hypostomatic (C. viticella, C. fargesii ‘Paul Farges’, C. heracleifolia, C. texensis ‘Princess Diana’, C. macropetala ‘Maidwell Hall’, and C. alpina ‘Pamela Jackman’), and amphistomatic leaves (C. ispahanica ‘Zvezdograd’ and C. tibetana). In C. integrifolia ‘Aljonushka’ leaves were hypostomatic, but few solitary stomata were also present on the adaxial surface. In the leaves of investigated taxa, the palisade coefficient ranged from 27.3% (C. alpina ‘Pamela Jackman’) to 49.9% (C. tibetana). The leaves also differed significantly in size. In particular, leaves of C. integrifolia ‘Aljonushka’ were almost ten times smaller than such of C. heracleifolia. As a result of UPGMA clustering, the plants that can survive in severe windy weather in open rocky areas, Clematis tibetana and C. ispahanica ‘Zvezdograd’, were joined in a separate cluster. The second cluster combined C. alpina ‘Pamela Jackman’ and C. macropetala ‘Maidwell Hall’ – cultivars blooming in the spring, during a period of significant difference in daily temperatures. A relatively small leaf area in plants from these two clusters may indicate an adaptation by reducing the transpiration area and general windage. The third cluster united the rest of investigated taxa, mostly – the mesophytic plants with a relatively large leaf area. However, due to similar morpho-anatomical structure of the leaf, the third cluster also comprised C. integrifolia ‘Aljonushka’ with the smallest leaves.