Proposals for quantifying two characteristics of tracheid pit arrangement in gymnosperm woods

MARTÍNEZ, LEANDRO CARLOS ALCIDES; PUJANA, ROBERTO ROMÁN; ZHANG, YI; RUIZ, DANIELA P.

Revista del Museo Argentino de Ciencias Naturales

MACN

Lugar: Buenos Aires; Año: 2016 vol. 18 p. 117 - 124

1514-5158

Arrangement of tracheid radial pits is frequently superficially mentioned in extant gymnosperm woodanatomy descriptions. However, pit arrangement is a key character for delimiting fossil-genera and fossil-speciesin gymnosperm woods. We propose two new indices for measuring and quantifying the radial pit arrangement infossil and extant woods. The first one, contiguity percentage index (Cp), indicates if the pits are contiguous (=incontact or touching) or overlapping with the adjacent upper and lower pits, and has values from 0 to 100%. Thesecond one, seriation index (Si), is an average of the seriation of the pits and is given as a numerical value equalor greater than 1; when pits are exclusively ordered in uniseriate columns the wood has a value of 1. These indicesare useful for quantifying the pit arrangement and for helping to characterize the type of radial pitting (araucarian/mixed/abietinean),particularly in fossil woods. These new indices also allow to express these two characters(contiguity and seriation) as continuous, making them more suitable for certain taxonomic or statistical analysis.