Chromosome numbers were determined for 125 accessions of 92 taxa of Mimosa from all five of Barneby's (Mem New York Bot Gard 65:1-835, 1991) taxonomic sections. For 69 species, 1 subspecies and 8 varieties, chromosome numbers are presented for the first time, for 6 species and 1 variety previously published data have been confirmed and for 3 species and 2 varieties different numbers were found. Results show that 74% of the accessions were diploid (2n = 2x = 26) and 26% polyploid, these mostly tetraploid (2n = 4x = 52) but with two triploid (2n = 3x = 39). These results double the number of Mimosa species for which the chromosome count is known from less than 10% previously reported to more than 20%, representing an important advance in the cytotaxonomy of this legume genus. These results together with literature data show that ca. 78% of Mimosa species are diploid. Polyploids are present in most of the taxonomic sections and in different lineages across the genus.No particular chromosome number is restricted to a given section or lineage. A possible relation between geography, species distribution, polyploidy and invasiveness was detected, however, further studies based on more accessions, especially from higher latitudes, are required before firm conclusions can be drawn.

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RESUMO -Os fungos micorrízicos arbusculares (FMA) promovem maior desenvolvimento de plantas, entretanto, a simbiose depende das espécies de ambos os simbiontes. Objetivou-se avaliar a interação entre porta-enxertos cítricos inoculados com espécies de fungos micorrízicos arbusculares. Testou-se três porta-enxertos citrangeiro 'Fepagro C37 Reck' [Poncirus trifoliata (L.) Raf. x Citrus sinensis (L.) Osbeck.], cunquateiro 'Hong-Kong' (Fortunella hindsii Swingle) e 'Trifoliata' (Poncirus trifoliata) inoculados com duas espécies de FMA (Glomus etunicatum W.N. Becker & Gerd. e Acaulospora sp.) e um tratamento não inoculado. Avaliou-se a altura (cm), o diâmetro do caule (mm), a área foliar (cm²/planta), o número de folhas, a massa fresca e seca da raiz e da parte aérea (g), o teor de reservas nos tecidos e a colonização dos FMA nas raízes. As espécies G. etunicatum e Acaulospora sp. colonizaram as raízes dos porta-enxertos, mas somente foram efi cientes para o 'Fepagro C37 Reck'. Poncirus trifoliata apresentou maior vigor em ausência de FMA. Palavras-chave: endomicorrizas, produção de mudas, simbioseABSTRACT -Interaction between rootstocks citrus and arbuscular mycorrhizal fungi. Arbuscular mycorrhizal fungi (AMF) support plant development, however, symbiosis depends on species of both symbionts. This study aimed to evaluate the interaction between rootstock citrus inoculated with species of arbuscular mycorrhizal fungi. Three rootstocks citrange 'Fepagro C37 Reck' [Poncirus trifoliata (L.) Raf. x Citrus sinensis (L.) Osbeck.], 'Hong-Kong' kumquat (Fortunella hindsii Swingle) and 'Trifoliata' (Poncirus trifoliate) were tested, inoculated with two species of AMF (Glomus etunicatum W.N. Becker & Gerd.and Acaulospora sp.) and a treatment not inoculated. We evaluated the height (cm), stem diameter (mm), leaf area (cm² / plant), leaf number, fresh and dry root and shoot weight (g), the level of reserves in tissues and the colonization of AMF in the roots. The species G. etunicatum and Acaulospora sp. colonized the roots of rootstocks, but they were only eff ective for 'Fepagro C37 Reck'. Poncirus trifoliata had the highest vigor in the absence of AMF.

RESUMO O conhecimento do porta-enxerto, do substrato e do recipiente são fundamentais para a defi nição do período necessário para produzir mudas cítricas de qualidade. O objetivo deste trabalho foi avaliar a emergência de plântulas e o desenvolvimento vegetativo

Polysomaty is the occurrence of cells with different ploidy levels in the same organ or tissue and there are records of this in root-tip cells of some Mimosa species. The objective of the present work was to verify the occurrence, possible cause and significance of polysomaty in a range of species of this genus. In root-tip cells of 68 accessions of 43 diploid and tetraploid Mimosa species, the percentage of polysomatic cells ranged from 5% to 87%. Pretreatment with the antimitotic paradichlorobenzene did not cause polysomaty but increased it in some accessions. When relating seedling root size and percentage of polysomatic cells, for most of the species a higher percentage of polysomatic cells was found in roots from 6 to 10 cm length. For M. scabrella ("bracatinga"), a comparative analysis of seedling root-tip cells and roottip cells from well-developed plants kept in pots in a greenhouse showed that polysomaty occurred only in the seedling root-tips. The data suggest that, in Mimosa, polysomaty occurs only for a short period of the seedling development, probably as a natural mechanism to accelerate its development and establishment.