Characterization of the seed reserves in Tillandsia (Bromeliaceae) and ultrastructural aspects of their use at germination

Abstract

The nature and the use of the reserves accumulated in the seed of Tillandsia, a markedly epiphyte genus, are especially important in consideration of the subsequent seedling development. As a matter of fact, the embryo radicle degenerates precociously without emerging at the germination and the sole function of the root system is that of anchoring to the substratum. The present cytochemical and ultrastructural study carried out on mature seeds has highlighted the presence of proteins and lipids, in both the endosperm and in the cotyledon, which are both well-developed; in addition, the endosperm contains starch and calcium oxalate. At germination the reserves, broken-down by enzymes, are absorbed by the cotyledon in whose epidermis ultrastructural modifications, correlated with this austorial function, appear. A part of the nutrients absorbed is initially stored in the large vacuoles, of aleuronic origin, of the cotyledon parenchyma. The result is a water uptake. It is in this manner that the water and necessary nutrient needs of the seedling are satisfied during early development.