Estudo ontogenético em frutos e sementes de Jatropha curcas L. (Euphorbiaceae)

Abstract

Jatropha curcas L. is a woody-shrubby species belonging to the Euphorbiaceae family, which is characterized by having an easy adaptation to semiarid environments, and fast growth. Its oilseeds aroused interest because they are mostly used as raw material to obtain oil for biofuel production. Knowing that the physiology of ripening of Jatropha fruits involves since the production of photoassimilates, to their formation and development, until the oil present in its seed, the aim of this study was to identify the structures and substances produced during ontogeny of their fruits and seeds. Botanical material, composed of fruits in ten stages of development, according with the days after anthesis, were collected from adult individuals of J. curcas, grown in an open field in the State of Alagoas. From this material were performed anatomical sections in serial microtome for characterization and monitoring of the ontogeny of Jatropha fruits and seeds. The fruits reach their maximum volume around 47 DAA, which suffers a reduction from 55 DAA, when they become dried and darkened. It was possible to see in many cases malformation or abortion of one or even two eggs. There is major presence of lactiferous all over fruit mesocarp, which may be branched or not, articulated or not. The seeds become fully ripe 13 DAA. The tegument is composed of testa and tegmen, where each one is clearly subdivided. The testa outermost layer has macrosclereids, fibers and lignified cells. However, it was observed the existence of some cells without lignification along the entire seed. Already from 18 DAA endosperm begins to be consumed, in consequence of an increase in the embryo’s body, which shows fully developed after 40 DAA, with evidence of a hypocotyl-radicle axis, besides cotyledons and primordial stem and root. The sclereids and fibers present in seminal tegument are responsible for the high rigidity in J. curcas seeds; however this characteristic, it seems, does not affect the germination process of the species.