Ontogenèse des canaux sécréteurs d'origine primaire dans le bourgeon de Pin maritime
In the bud of Pinus pinaster Ait., two resin ducts are formed at the base of each very young scale on each side of the procambial strand. They differentiate in the acropetal and basipetal directions as do the vascular tissues. During the basipetal differentiation, the resin ducts from each scale anastomose in a definite way: the left resin duct of each scale is connected with the right duct of the n – 8 scale rank and the right duct, with the left duct of the n – 5 scale rank. The resin canal system of the shoot is then constituted of only 13 resin ducts. The resin ducts of the maritime pine are formed on a schizolysigenous pattern: a schizogenous process induces the formation of the lumen; then a transitory stage with two secretory layers takes place before a lysigenous process which enhances the enlargement of the duct lumen. Observations were done using light and electron microscopy.