STRUCTURAL AND CHEMICAL CHARACTERIZATION OF THE XYLEM OF THREE BLECHNUM ARBORESCENT SPECIES

LUNA, M. L.; RAMOS GIACOSA, J. P.; GIUDICE, G. E.; FERNÁNDEZ, P. V.; CIANCIA, M.; SAPARRAT, M. C. N.

IAWA JOURNAL

INT ASSOC WOOD ANATOMISTS

Año: 2015 vol. 36 p. 3 - 21

0928-1541

This contribution details the study of the xylem in three arborescent species of Blechnum section Lomariocycas from adaptive and evolutionary points of view using SEM, TEM, FT-IR spectroscopy and sugar composition analysis. Overall structure of root and rhizome metaxylem tracheids was similar in the species analyzed, since they showed various facets mainly with scalariform pitting. Different degrees of pit membrane thickness and porosity were observed microscopically depending on a tracheid?s stage of maturation. Sometimes, roughly rounded deposits resembling vestures were noted in the outer pit apertures of the tracheids. Under TEM, thickenings like one-sided tori appeared on the tracheid side of tracheid to parenchyma blind pits; some parenchyma cells showed, in addition, features of transfer cells. As the increase in stature creates new constraints in terms of biomechanical support and water transport in plants, it is assumed that the characteristics found in Blechnum xylem may be related to an improvement in the flow of water and to the prevention of embolism. Chemical analyses of roots and rhizomes of B. yungense revealed similar levels of G-type lignin deposited in the xylem cell walls. Such lignin is the most common in ferns, including other arborescent genera. Preliminary results about cell wall polysaccharide composition gave similar results for root and rhizome xylem, suggesting cellulose, xyloglucans and xylans as major components with lesser amounts of mannans and pectins. A higher amount of cellulose could be present in xylematic tissue of the rhizome. This information is discussed in relation to its contribution to support of the plant body.