O gênero Croton L. (Euphorbiaceae) em Pernambuco, com ênfase nas espécies da microrregião do Vale do Ipanema

Abstract

Croton L. is the second bigger genus in the family Euphorbiaceae s. s. with about 1.200 species spread, predominantly, in the American continent. The objective of this work was to study the diversity of the genus Croton in Pernambuco, especially the species occuring in the microregion of the Vale of Ipanema. The study was based on the morphological analysis of specimens of the herbariums BHCB, ESA, ESAL, HST, HUEFS, IAN, IBGE, IPA, PEUFR, R, UFP, UB, VIC, especially of materials collected in the differents phytogeographic areas of Pernambuco, complemented by the analysis of pictures of types and original descriptions. They were found 35 species distributed, mainly, in the phytogeographic zone of the Caatingas. Only Croton polyandrus Spreng. e C. selowii Baill. Occurring in the coastline, in restinga vegetation and C. argenteus L., C. jacobinensis Baill. and C. triqueter Lam. that are observed in the forest zone. C. glandulosus L., C. heliotropiifolius Kunth, C. hirtus L´ Hér. e C. lundianus (Didr.) Müll. Arg. with wide distribution. For microregion of the Vale of Ipanema 15 species were recorded: C. adamantinus Müll. Arg., C. argyrophyllus Kunth., C. blanchetianus Baill., C. echioides Baill., C. glandulosus, C. grewioides Baill., C. heliotropiifolius, C. hirtus, C. lundianus, C. microcarpus Desv ex. Ham., C. nummularius Baill., C. rudolphianus Müll. Arg., C. tetradenius Baill., C. urticifolius Lam. e C. virgultosus Müll. Arg., being four of them (C. microcarpus, C. nummularius, C. rudolphianus, C. virgultosus) restricted to the complex of mountain ranges of the São José plateau, in Buíque. The species differed, especially, for the type of trichomes, presence or absence, morphology and position of the foliar nectaries, forms of the pistillate sepals and number of ramifications of the styles. Identification keys, descriptions, comments about geographic distribution, habitats and phenology, together with illustrations of diagnostic characteristics of the species are provided. It was still set up the study of the foliar nectaries (NFs) of 12 species ocurring in the Northeast through scanning electron microscopy and optical. The species possess NFs distributed on the foliar blade and petioles. The NFs petioles were shown variables as for their location, amount, size and form, they could be used as a character diagnosis. The shape of NFs was were found the following types: pateliforms (4 spp.), lenticular (2 spp.), discoid (2 spp.), cylindrical (1 sp.), globose (1sp.) and obcampanulate (1 sp.).