Araçà-boi is a fruit, which awakes great interest for presenting pulp of quality. Their seeds are recalcitrant and present a relatively short period of viability. The water absorption by seeds is a mechanism of growth resuming of the embryo with a subsequent of the tegument breakage by the radical. The seed electric conductivity is a vigor testing is directly related to the membrane permeability. Study of the curve of water absorption by the araçá-boi seeds will contribute to characterize their germination process. In this context, studies concerned with seeds were conducted, which characterized the mass, biometrics, water content, electric conductivity and water imbibition by seeds. It was found that the population of plants established in Manaus-AM produces small, medium and large seeds and which present 70.2, 68.2 and 47.5% of moisture. The greatest water increase takes place in the first hour of absorption, regardless of the size of seeds and water absorption velocity is not influenced by their size. The imbibition curves characterized in the 144-hour period, independent of the size of seeds, show changes of two physiological phases. Both the large and medium seeds present smaller conductivity values, obtaining smaller percentages of germination for possessing increased vigor indices.

ABSTRACT. Studies addressing chromosome variations have elucidated many points regarding the taxonomy of the Orchidaceae. Epidendrum L. besides being one the largest orchid genera, present remarkable morphological, and inter-and intraspecific chromosome variations. Thus, based on a previous report on flower color variation in individuals of E. ibaguense (magenta, pink, white, and red), our aim was to determine its chromosome number and test whether this trait is associated with flower color variation in natural populations on the Tepequém's Tepuy, Roraima. Root apices were pre-treated with 8-hydroxyquinoline at 4°C for 24 h and subsequently submitted to conventional cytogenetic procedures. Slides with the best spreading and contraction of chromosomes were photographed under light microscopy. Chromosome number was determined by counting at least 10 mitotic metaphase cells per individual. The types of interphase nuclei were determined for 30 nuclei per individual. E. ibaguense presented intra-and interpopulation variation in chromosome number, with 2n = 58, 72, and 76. The chromosome number 2n = 58 was most commonly found in individuals with magenta, pink, and white flowers, while the remaining two chromosome numbers occurred mostly in red-flowered individuals. The types of interphase nuclei were associated with the chromosome number. Individuals with 2n = 58 presented a predominance of semi-reticulated nuclei, while in those with 2n = 72 and 76 the nuclei were predominantly non-reticulated. The dominance of disploidy in E. ibaguense suggests that this cytotype provides this species with a territorial advantage and a higher reproductive success, possibly contradicting the polyploid hypothesis. Our results suggest that chromosome number may not represent a reproductive barrier in genus Epidendrum.

Abstract:The Araca-boi is a native fruit of the Amazon region and its fruits have great potential for agro-industrial use due to the intrinsic characteristics of the pulp. The seeds are dormant and the primary cause could be due to the presence of inhibiting chemicals germination and can also be caused by the impermeability in tegument. The objective of this study was to assess the osmopriming efficiency promoted by Sucrose (C 12 H 22 O 11 ) and Potassium Nitrate (KNO 3 ) on germination of seeds of araca-boi in different immersion times. Thus, the seeds were osmoconditioned in following solutions: C 12 H 22 O 11 , KNO 3 , KNO 3 + C 12 H 22 O 11 and H 2 O, by period of 6, 12 and 24 h. Throughout of 70 days were evaluated the germination percentage and germination rate (index). The experiment is based on a completely randomized in a factorial analysis 4x3 with four replications of 10 seeds. The osmopriming of Araca-boi seed in KNO 3 solution was shown to be efficient both to promote germination and the germination rate. The Araca-boi seeds osmoconditioned in KNO 3 solution has an average efficiency of 99% in the germination percentage up to 70 days. The osmopriming period showed no influence on seed germination of the seeds of Araca-boi.Resumo: O araçá-boi é uma frutífera nativa da região Amazônica e seus frutos apresentam grande potencial de aproveitamento agroindustrial devido às características intrínsecas de sua polpa. Suas sementes são dormentes e a principal causa pode ser devido à presença de substâncias químicas inibidoras da germinação e também pode ser causada pela impermeabilidade do tegumento. Neste contexto, o objetivo neste trabalho foi avaliar a eficiência do osmocondicionamento promovido por Sacarose (C 12 H 22 O 11 ) e Nitrato de Potássio (KNO 3 ) na germinação de sementes de araçá-boi, em diferentes tempos de imersão. Para tal, as sementes foram osmocondicionadas em soluções de C 12 H 22 O 11 , KNO 3 , KNO 3 ,+ C 12 H 22 O 11 e H 2 O, por períodos de 6, 12 e 24 h. Foram avaliadas no período de 70 dias, a porcentagem de germinação e a velocidade de germinação (índice). O delineamento utilizado foi o inteiramente casualizado em fatorial 4x3, com 4 repetições de 10 sementes. O osmocondicionamento de sementes de araçá-boi em solução de KNO 3 é eficiente para promover a germinação e a velocidade de germinação. Sementes de araçá-boi osmocondicionadas em KNO 3 apresentam porcentagem de germinação de 99% até os 70 dias. O período de osmocondicionamento não influencia na germinação das sementes de araçá-boi.Palavras-chave: Eugenia stipitata. Dormência. Priming.

Kexin-like proteins are proteinases belonging to the subtilase family which are involved in the processing of pro-proteins to their active forms. In fungi, kexin-like proteins are involved in several important cellular processes, including mating and dimorphism. Paracoccidioides brasiliensis, the causative agent of paracoccidioidomycosis undergoes a thermo-regulated dimorphic transition which is essential for the establishment of the infection. Although the molecular mechanisms which rule this process are still unknown, several genes identified in P. brasiliensis have been implicated in dimorphism, including kex2, a kexin-like protein. In this work we have used the baker's yeast Saccharomyces cerevisiae as a host to perform heterologous expression analysis of the P. brasiliensis kex2 gene. Our data shows that kex2 can complement the functions of a S. cerevisiae kex2 mutant strain and could therefore be considered its functional homologue.