Bordered pits, degradation

Protective effects of chromic acid and ferric chloride treatments on surface degradation also were observed on radial surfaces. The preservation of both simple and bordered pits in woods treated by these inorganic salts was observed. At a 10% chromic acid treatment concentration, the structure of the pits retained most of the original shape after 1000 h of UV irradiation. The diagonal microchecks passing through the bordered pits in radial walls of tracheids, however, can still be observed (Figure 30). 

The degradation of secondary cell walls also affects the bordered pits. 

The pit chambers are reduced to what ontogenetically is called the initial pit chamber, and the pit membranes are dissolved or detached. Fengel (15) reports pit membranes in fossil spruce to be quite resistant. However, in tissues where all secondary cell walls have been degraded we have not seen any pit membranes in bordered pits. 

Half-bordered and bordered pits on exposed radial surfaces are severely degraded by UV light. 

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