Distribution, Size and Effective Aperture Area of the Inter-Tracheid Pits in the Radial Wall of Pinus Radiata Tracheids

The distribution, size and effective aperture area of inter-tracheid pits were studied in a 29-year-old plantation-grown tree of Pinus radiata by means of light and electron microscopy. It was found that the number of pits per tracheid in the first ten years is related more to tracheid length than to the age of the wood. Beyond the tenth year, the number of pits per tracheid is mainly related to the age of the wood, regardless of tracheid length. In addition, there is a positive linear relationship between tracheid diameter and pit diameter, indicating that the larger tracheids contain larger pits. The percentage of the effective aperture area per mrn length of radial tracheid wall is discussed, in relation to the 'percentage of aspirated pits and total area of pit aperture per tracheid.