Morfogênese, caracterização temporal e efeito da remoção das reservas em estádios pós-embrionários de três espécies de palmeiras (Arecaceae: Arecoideae)

Abstract

This work presents morphological and anatomical data to understand the process of organogenesis during the initial growth of three Amazonian palms: Astrocaryum acaule, Attalea attaleoides and Attalea microcarpa. These species present differences in the type of post-germinative development, as well as in their internal morphology, being these more pronounced among species of different genera. In Astrocaryum acaule the germination is adjacent, with formation of a coleoptile above the cotyledonary sheath. The germination is unequal, varying from 14 to 250 days for emission of the germinative bud. The initial root system differs in the hypocotyl-radicle region, below the insertion of the leaf primordia, forming first a lateral root, whereas the primary root has posterior emergence. The first eophyll, bifid, is expanded to 120 days after the protrusion of the germinative button. Attalea species differ in the time of emergence of the germinative bud, with an average of 171 days for A. attaleoides and 15 days for A. microcarpa, with a wide variation in the period. Both have early initial growth, with apocole lengthening, no coleoptile present, have an evident and persistent primary root, with lateral roots traversing through the cotyledonary sheath. Attalea microcarpa can branch off the primary root and emit roots of the apocole. By means of histochemical tests mucilages, starch and proteins were detected in adventitious roots and in the primary root of the species. The first eophyll, lanceolate, is expanded about 113 days after the emission of the germinative button in A. attaleoides and 145 days in A. microcarpa. The seeds of the species have a tegument with a layer in Astrocaryum acaule and two layers in Attalea followed by an endosperm where a zone of degradation is formed, that increases with the growth of the haustorium, evidenced by the dissolution of the endosperm cell walls. In Attalea, in the phase of expansion of the first eophyll this zone of degradation is close to the integument of the seed. The centesimal composition of all species was investigated, revealing the predominance of lipids and carbohydrates as the representative reserves of the seed. The three species have similar composition by the qualitative analysis of the histochemical tests in the endosperm and haustorium. However, the detection of lipids and starch in the haustorium was evident only from the stages after the emission of the germinative button. The data presented here can support studies with the propagation of palm species for economic purposes and complementary ontogenetic studies. It is also hoped that the information in this study will broaden the database on Amazonian flora, palms, and how to conduct ontogenetic studies within the group be addressed in future works. We suggest working with different taxa in order to answer other questions related to the organogenesis of structures involved in plant growth, which may have phylogenetic, autoecological or adaptive importance.