The pyrolytic behavior of Pinus halepensis needles observed by transmission light microscopy and stereoscopy

Two microscopic techniques were used for monitoring the changes that occur during the pyrolysis of Pinus halepensis needles at 100, 200, 250, 300, 350, 400 and 500°C. The changes were monitored by transmission light microscopy (LM) and stereoscopy. The following were observed with increasing temperature: (1) deformation of the transverse section; (2) loss of the cuticle layer and cracking of the outer layer; (3) degradation of lignin (a basic component of pine needles); and (4) tar and char formation on the external surface. These changes were attributed to chemical and physical phenomena during the pyrolysis procedure.