| dc.description.abstract | The seed coat externally covers the seed, and its primary function is to protect the embryo. In
mature seed, testa, and tegmen, if differentiated, can prevent germination if there is
impermeability. Impermeable seed coats promote physical dormancy, which is usually related
to one or more layers of palisade cells that often occur in the testa and to hydrophobic substances
embedded in the walls of these cells. Among Leguminosae species, physical dormancy is very
common. An important aspect to investigate is the structural since, despite being well known,
there are still gaps in the structural characterization of the typical testa of Leguminosae in
several works. Another interesting element is the environment’s influence, maternal and
storage, on the acquisition of physical dormancy among legumes. It is known that
environmental conditions influence the seed moisture content, which, in turn, is related to the
percentage of seeds with physical dormancy. There are records of species in which the
impermeability is more pronounced when the water content of the seeds is lower. However,
there are few references to structural aspects that show the influence of these aspects on the
presence or absence of physical dormancy depending on the water content. Therefore, the
objectives of the present work are: to characterize, in detail, the testa layers of Leguminosae
species, investigating the chemical nature of the cell walls; characterize the ontogenesis of the
testa of Erythrina speciosa, with a main focus on the mucilaginous stratum; verify the influence
of the environment on physical dormancy before and after dispersal; and evaluate the influence
of the seed coat structure on the acquisition of pre- and post-dispersion physical dormancy. The
terms macrosclereids and osteosclereids are often misused when they come to seed coats; to
avoid the dissemination of incorrect data, the chemical composition of the cell layers that make
up the testa must be investigated. The sensu lato cuticle in Leguminosae seeds may not contain
lipids in its composition, and, sometimes, the outermost layer of the seed is made up only of
pectic compounds; therefore, the term mucilaginous stratum is the most appropriate term to
adopt. The mucilaginous stratum is essential for the acquisition and maintenance of physical
dormancy in species of Leguminosae, as we have shown experimentally. | |
