Spore morphology and wall ultrastructure of Blechnum L. species from North West Argentina

Spores of Blechnaceae species that grow in northwest Argentina were studied. These are: Blechnum australe subsp. auriculatum, B. austrobrasilianum, B. brasiliense, B. cordatum, B. laevigatum, B. mochaenum var. squamipes, B. occidentale, B penna-marina, B. sprucei and B. tabulare. The study was performed with light microscope (LM), transmission electron microscope (TEM) and scanning electron microscope (SEM). The spores are monolete of 31.5–104 µm in equatorial diameter and 21–75 µm in polar diameter. The exospore is 0.6–3.5 µm thick, plane or scabrate and in section it is two-layered. According to the plane of sectioning, and especially in immature material, interwoven channels are evident. The exospore structure is blechnoid and similar in all taxa analysed. The perispore is 0.4–3.0 µm thick and plane, rugulated or folded. Its surface has verrucae, rugulae and perforations. In section it is two-layered. The outer layer is single stratified and the inner layer is three-stratified. Scattered spherules are also present on the surface and globules are detected in the perispore. In the analysed taxa the perispore has the greatest variability at specific and infraspecific levels and five structural types are observed. Differences were found among the studied taxa in the characteristics of the medium stratum. Additionally, in B. cordatum the structural elements are also superficially observed on and between the folds. The differentiated structural types would not find any correspondence with the ornamentation patterns of the species here analyzed. The diversification found in spore characteristics observed in this study, could be valuable for systematic and phylogenetic studies.