Germination and morphogenesis in vitro of mahogany (Swietenia macrophylla King) / Germinação e morfogênese in vitro de mogno (Swietenia macrophylla King)




The objective of this work was to develop techniques of in vitro regeneration of mahogany (Swietenia macrophylla), through epicotyls segments, inverted epicotyls and leaf explants from mahogany plantlets germinated in culture medium. Also the best concentration and time for seeds sterilization and the sterilizing agent were determined, as well as the best sowing position of the seed for germination. After removing the teguments of the seeds, they were sterilized in sodium hipochlorite solutions on concentrations 0; 2,5 and 5,0% (v/v), keeping them soaked by 10, 20, 30 and 40 minutes and inoculated in the culture medium in two positions: a) position 1 - with the concavity of the flat part turned upward, and b) position 2 - with the concavity of the flat part turned down. After the inoculation the seeds were kept in growth room with controlled temperature and photoperiod. The factorial design was entirely casual, with 3 x 4 x 2 (sodium hipochlorite levels x times of soaking x position of the seed), totaling 24 treatments with 3 repetitions. The germination stage and microorganism contaminations were evaluated at 12, 18, 24 and 30 days after germination. In general, the best treatments were the seed sterilization soaked in 2,5 and 5% of sodium hipochlorite at 30 and 20 minutes, respectively, and both inoculated in the position 2, also these treatment presented the greatest germination rate (48%) and the lowest rates of microorganisms contamination. About position, it was detected a significant difference for the 24 and 30 days after inoculation, with the greatest averages for the seeds inoculated in the position 2. The leaf explants inoculated on MS culture medium supplemented with different concentrations of the growth regulator picloram (4-amino-3,5,6-tricloropicolinic acid, 0; 0,6; 1,2; 2,4 and 4,8 mg L-1) with the number of explants with callus, callusing intensity and callus texture, being evaluated at 20, 30 and 40 days. At the end of 40 days, embryogenesis was not observed, only formation of compact and white callus. For the epicotyl segments, inoculated in half MS supplemented with combinations of BAP (6-benzilaminopurine) and ANA (naphthalenacetic acid), calogenesis was observed in most of the explants, with formation of greenish compact callus in the extremities of the explants. The inverted hypocotyls, inoculated in half MS supplemented with BAP (0; 0,5; 1,0; 2,0 and 4,0 mg L-1) presented shoot elongation in the cotiledonary and preexistent knots. It was also observed in this explant type a discharge oxidation rate in the explant in contact with the culture medium.


germination swietenia macrophylla swietenia macrophylla mogno essências florestais propagação silvicultura in vitro culture morphogenesis germinação mahogany propagation cultivo in vitro morfogênese

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