Wilson Vicente Souza Pereira

Microenxertia ex vitro para eliminação do vírus CABMV em maracujá-azedo

O objetivo deste trabalho foi avaliar diferentes meios de cultura, utilizados sobre o ponto da enxertia, na microenxertia ex vitro para a eliminacao do Cowpea aphid-borne mosaic virus (CABMV), em plantas de maracuja-azedo (Passiflora edulis Sims f. flavicarpa Deg.). Apices caulinares, provenientes de plantas infectadas, foram microenxertados em plântulas obtidas pela germinacao de sementes em substrato comercial esterilizado. Foram conduzidos experimentos com a microenxertia realizada no hipocotilo e no epicotilo, e foram utilizados cinco meios de cultura, que diferiam na concentracao de fitorreguladores, aplicados no local da enxertia. O indice medio de microenxertos com folha expandida foi de 27,22 e 32,22%, quando a microenxertia foi realizada no hipocotilo e no epicotilo, respectivamente. Na microenxertia realizada no hipocotilo, nao houve efeito da aplicacao de meios de cultura. Na microenxertia realizada no epicotilo, o meio MS acrescido de 0,1 mg L-1 de AIB e 1 mg L-1 de BAP proporcionou 53,3% de microenxertos com folha expandida, numero superior aos demais tratamentos e maior desenvolvimento das brotacoes. A indexacao realizada pelo teste ELISA indireto, 80 a 100 dias apos a microenxertia, mostrou que 93% das plantas testadas nao apresentavam virus detectavel.

Loss of desiccation tolerance in Copaifera langsdorffii Desf. seeds during germination

This study evaluated the loss of desiccation tolerance in C. langsdorffii seeds during the germination process. Seeds were imbibed for 24, 48, 72, 96, 120 and 144 hours and dried to the initial moisture content, kept in this state for 3 days after which they were submitted to pre-humidification and rehydration. Ultraestructural evaluations were done aiming to observe the cell damage caused by the dry process. Desiccation tolerance was evaluated in terms of the percentage of normal seedlings. Seeds not submitted to the drying process presented 61% of normal seedlings, and after 24 hours of imbibition, followed by drying, the seeds presented the same percentage of survival. However, after 48 hours of imbibition, seeds started to lose the desiccation tolerance. There was twenty six percent of normal seedlings formed from seeds imbibed for 96 hours and later dried and rehydrated. Only 5% of seeds imbibed for 144 hours, dried and rehydrated formed normal seedlings. At 144 hours of imbibition followed the dry process, there was damage into the cell structure, indicating that the seeds were unable to keep the cell structure during the drying process. Copaifera langsdorffii seeds loses the desiccation tolerance at the start of Phase 2 of imbibition.

Microenxertia interespecífica ex vitro em maracujazeiros

This study aimed at evaluating the effect of Passiflora species used as rootstocks on the success and development of ex vitro interspecific micrografting, and at anatomically characterizing the region where it is done. Stem apices of Passiflora edulis f. flavicarpa were grafted onto the hypocotyl of P. alata, P. cincinnata, P. edulis, and P. setacea seedlings. The micrografting development, the occurrence of adventitious shoots in rootstocks and the percentage of micrografts with expanded leaves were evaluated. The rootstocks were subjected to anatomical and histochemical evaluation. Micrograft development and adventitious shoot number were higher when P. edulis rootstocks were used, and lower for rootstocks of P. setacea and P. alata. P. edulis, P. cincinnata, P. alata, and P. setacea rootstocks developed 30.3, 10, 1.6, and 0% of micrografts with expanded leaves, respectively. The histological evaluation revealed increased thickness of the cortical region in rootstocks of P. edulis, while in P. setacea a lower number of cortical layers, increased phloem fibers, and increased alkaloids were observed, characteristics that negatively influenced the micrografting outcome.

Maturation and Desiccation Tolerance in Seeds of Sesbania virgata (Cav.) Pers.

The maturation process of Sesbania virgata seeds was investigated through fruits and seeds at different maturation stages, where they were described morphologically. For the seeds, fresh and dry mass and moisture were determined and structural analysis of the tegument under a light microscope was performed. Germination tests in the presence and absence of drying and the electrophoretic profile of heat resistant proteins were also performed. The results showed that the seeds reached physiological maturity at 44 days after anthesis (DAA), evidencing a secondary cell wall. The acquisition of desiccation tolerance was observed at 44 DAA, with the seeds responding to the drying treatment. Protein bands were observed from 32 DAA, which remained constant until the end of maturation. These results allowed the characterization of the development and acquisition of desiccation tolerance in S. virgata seeds.

Aspects of Peltophorum dubium Sprengel (Taubert) seeds in an aerial seed bank

Knowledge concerning natural regeneration strategies is important due to the effect of natural regeneration on the local ecosystem. The aim of this study was to examine the ecophysiological aspects of the Peltophorum dubium aerial seed bank. Fruits were harvested monthly, before and after seed maturation, from selected trees in the municipality of Lavras, MG, Brazil, for determination of moisture content, acquisition of tolerance to desiccation, seed viability, maintenance of dormancy, and mean germination time. Physiological maturity of the species was attained in June, when low moisture content, maximum dry matter, and high germination percentage were observed. We found that there was no change in dormancy, in germination percentage, or in the protein profile of seeds during the period they remained in the aerial seed bank. The P. dubium species creates an aerial seed bank of short serotiny, with fruits remaining attached to the tree for 9 months.