Occurrence and ecological characteristics of C4 dicot and Cyperaceae species in the Hungarian flora

Abstract

The non-graminaceous wild flora of Hungary was screened for C4 plants by using the stable carbon isotope ratio, the leaf anatomy and the photosynthetic carbon dioxide compensation concentration to determine the photosynthetic pathway type. On the whole, 31 C4 species (native or naturalized) were found in the Amaranthaceae, Chenopodiaceae, Cyperaceae, Euphorbiaceae, Portulacaceae and Zygophyllaceae families. Together with the 26 C4 grass species (Poaceae) reported earlier (Kalapos 1991), a total of 57 wild C4 species occur in Hungary, which forms 2.6 % of the country's angiosperm flora. This figure is somewhat higher than what was expected on climatic grounds, a fact probably due to certain edaphic conditions favouring C4 plant growth. In Hungary, the C4 species are predominantly annuals growing in open habitats such as dry grasslands, inland saline areas, temporarily exposed riverbeds and disturbed sites. In comparison with C3 plants, the C4 species have higher temperature and light preferences, and their phenology lags behind that of the C3 plants. These differences might account for C4 plants being usually excluded from productive biotopes in Hungary, where the C3 canopy may become closed during the growing season before C4 plants can start their ontogenetic development. Ecological properties of C3 and C4 plants differ considerably in the Cyperaceae, but much less in the Chenopodianceae family. Among C4 annuals naturalized aliens are common, most of which colonized hungary in the last two centuries. Increasing preponderance of C4 plants is anticipated in the future as a consequence of possible climate changes and the ever increasing human impact on terrestrial vegetation.