Reprodução assexuada de Ipomoea carnea Jacq. e sua influência no banco de sementes em área de caatinga no Sertão Paraibano.

Abstract

Ecosystems have been altered by man by the introduction of plants to achieve several purposes. Many of these species get adapted to the new environmental conditions, disseminate and cause economical and ecological impacts. The economic impacts consist mainly of the reduction in the productivity of other species and in the costs to control the introduced species. The ecological alterations are difficult to preview and usually unknown due to the lack of studies about the interaction between the introduced and the autochthonous species. In the Caatinga Biome, studies have shown serious modifications in the floristic composition, diversity and richness of seed bank and vegetation in sites occupied by Prosopis juliflora, Parkinsonia aculeata, Cryptostegia madagascariensis and other species. Ipomoea carnea Jacq. is a Convolvulaceae from South America, observed in all Brazilian biomes, and its leaves and tender branches contain a neurotoxic compound known as swainsonia. It grows on sandy soils with low levels of nutrients and organic matter, especially on sites seasonally flooded, where it develops dense populations with individuals bearing flowers and fruits during the whole year. Although it produces many seeds, reproduction by rooting of the decumbent stems predominates and results in many entangled stems in the sites colonized by this species. This study has the objective to verify the effects of I. carnea on seed bank, as well as the processes of its asexual propagation. Seed bank study was based on soil+litterfall samples collected from five areas in the Sertão region of Paraíba colonized by I. carnea. Propagules present in seed bank showed to be similar in the studied areas in terms of floristic composition, with predominance of herbs, low diversity and species richness, and emergency of few I. carnea saplings. In the propagation study, 30-cm long stakes cut from decumbent or vertically growing stems showed high percentage of rooting and elevated potential of vegetative propagation. Keywords: Autochthonous species. Environmental impacts. Biological invasion.