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

BOERI P; ARAMBARRI, A; COLARES, M; ROMERO, M; DALZOTTO D; RANGEL CANO RM; CABRERA PONCE, JL; BARRIO, D; SHARRY S

Somatic Embryogenesis and other vegetative propagation in forest trees

Universidad Nacional de La Plata

Lugar: La Plata; Año: 2017; p. 109 - 118

Histological methods contribute significantly to the understanding of in vitro tissue culture systems, since they provide information 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 and various bio-active compounds. Cotyledons placed in the induction medium were used to induce somatic embryogenesis (Sharry et al. 2006; Boeri et al. 2016). Explants of both species differentiated either morphogenic or non-morphogenic callus. In chinaberry there were no noticeable differences in appearance between the embryogenic and organogenic calli, since both embryogenesis and organogenesis took place in the same type of callus. This callus originated both organs and embryos. Microscopic analysis showed the coexistence of meristemoids, shoots, somatic embryos 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 process took place in different types of cells with intense cell divisions that were located in regions distributed randomly. The cne were rounded or elongated, had thin walls and little cytoplasm. The ce were rounded, small and relatively thickwalled and 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 from superficial cells from existing ce cells. Divisions observed in these surface cells affirm the unicellular origin of embryos obtained in alpataco and chinaberry cultures. The different stages of embryogenic development observed in both 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 that not all cells differentiate into somatic embryos at the same time, it was possible to observe all the stages of development of the embryo in the same callus. Finally, somatic embryos germinated normally. Somatic embryogenesis was highly similar for both species even though no systematic relationship existed between the species studied. The explants and environmental conditions used for both species were similar.