Structure and ultrastructure of Pinus canariensis needles

The present study using light, transmission and scanning electron microscop y contains information about the structure of the needles of Pinus canarien sis, an endemic pine of the Canary Islands. As a three-needled species, the y have a triangular shape in transverse section being the abaxial side hemi spherical. The deeply sunken stomata and the waxes covering the epidermal c ells as well as the epistomatal chamber, constitute a good adaptation to th e loss of water. The mechanical tissue below the epidermis contributes to a higher drought resistance and to maintain the shape of the long needles as a skeletic tissue. The ultrastructure of mesophyll cells, transfusion tiss ues as well as endodermis and resin ducts is also described. The results of this study should be used as reference data for further investigations of physiological, biochemical and ultrastructural responses of this species to environmental variations due to pollutants and different altitudinal and e xposure situations.