Histological analysis of somatic embryogenesis of Melia azedarach L. and Prosopis alpataco Phil.

BOERI P; ARAMBARRI A; COLARES M; ROMERO ALVES M; DALZOTTO D; RANGEL CANO R; CABRERA PONCE; BARRIO DA; SHARRY, S

La Plata

Conferencia; The Fourth International Conference of the IUFRO Unit 2.09.02: Somatic Embryogenesis and Other Vegetative Propagation Technologies; 2016

IUFRO

Histological methods contribute significantly to the understanding of in vitro tissue culture systems, since they provideinformation that enable us to make the right decisions to optimize in vitro propagation protocols. Melia azedarach(chinaberry) and Prosopis alpataco (alpataco) are two multipurpose woody species. They provide wood, food andvarious bio-active compounds. Cotyledons placed in the induction medium were used to induce somaticembryogenesis (Sharry et al. 2006; Boeri et al. 2016). Explants of both species differentiated either morphogenic ornon-morphogenic callus. In chinaberry there were no noticeable differences in appearance between the embryogenicand organogenic calli, since both embryogenesis and organogenesis took place in the same type of callus. This callusoriginated both organs and embryos. Microscopic analysis showed the coexistence of meristemoids, shoots, somaticembryos and vascular tissue, as well as still dedifferentiated cells. Prosopis cotyledons produced only somaticembryos. In both, pro-embryogenic (ce) and non-embryogenic (cne) cells were observed. A re-differentiation processtook place in different types of cells with intense cell divisions that were located in regions distributed randomly. Thecne were rounded or elongated, had thin walls and little cytoplasm. The ce were rounded, small and relatively thickwalledand had a dense cytoplasm and a prominent, deep red nucleus which are typical characters of meristematic andpro embryogenic cells. Embryogenesis was initiated in individual cells located in the periphery of the callus and fromsuperficial cells from existing ce cells. Divisions observed in these surface cells affirm the unicellular origin ofembryos obtained in alpataco and chinaberry cultures. The different stages of embryogenic development observed inboth species were similar to embryogenesis in vivo; suggesting the genetic potential of the plant is being used. Theformation of somatic embryos was a continuous process during the period of incubation of the explants. Given thatnot all cells differentiate into somatic embryos at the same time, it was possible to observe all the stages ofdevelopment of the embryo in the same callus. Finally, somatic embryos germinated normally. Somaticembryogenesis was highly similar for both species even though no systematic relationship existed between the speciesstudied. The explants and environmental conditions used for both species were similar.