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.
R e~u le 17 juin 1981 VINDT-BALGUERIE, E. 1982. Etude au microscope Clectronique A balayage de la bulbille de Huperzia selago (L.) Bernh. (Lycopodium): mCristkme apical, initiation foliaire et phyllotaxie. Can. J. Bot. 60: 667-673. L'apex de la bulbille du Lycopode Huperzia selago (L.) Bernh. (Lycopodium) a Ct C CtudiC au microscope Clectronique A balayage. Du point de vue ontogCnique, des variations de la forme et de la taille du mCristkme apical ont CtC observkes: celui-ci, au cours du plastochrone, passe par des phases successives d'aires minimale et maximale. Grdce au microscope Clectronique A balayage, l'aspect quantitatif du problkme (surface et nombre de cellules) peut aussi Ctre abordC. I1 a CtC dCmontrC qu'au point vCgCtatif de la bulbille mGre les feuilles sont initiCes une A une et sont disposCes selon deux hClices. VINDT-BALGUERIE, E. 1982. Etude au microscope Clectronique A balayage de la bulbille de Huperzia selago (L.) Bernh. (Lycopodium): mCristkme apical, initiation foliaire et phyllotaxie. Can. J. Bot. 60: 667-673. The shoot apex of the bulbil of Huperzia selago (L.) Bernh.(Lycopodium) has been examined by scanning electron microscope. From an ontogenic point of view, changes in shape and size have been observed in the apical meristem. Successive minimal and maximal areas of this meristem are described during a plastochron. Area and cell number are also quantified with the scanning electron microscope. Only one leaf is initiated at the beginning of each plastochron, and the two contact parastichies observed in the shoot apex of the mature bulbil are two foliar helices.
In the very young sporeling of Phyllitis scolopendrium (L.) Newman, the leaf initium situated at the upper extremity of one of the two helices was microsurgically destroyed. In 5 specimens out of 24 the shoot developed only one foliar helix. This is proven by the contiguous disposition of the successively formed leaves (original phyllotactic diagram) and by the observation of only one focus of morphogenetic activity in the initiating ring, thus supporting the concept of the existence of only one foliar generating centre. When the foliar initium is destroyed, the shoot stelar differentiation is also modified: the vascular system develops a protostele, then a siphonostele. As soon as the first new leaf appears after wounding, the normal solenostele is restored. [Translated by the Journal]
An ontogenic study of the primary resin ducts was carried out from the embryo to the 2-month-old seedlings stage in Pinus pinaster Ait. and revealed two separate systems, the hypocotyl-radicular ducts and the epicotylar ducts. In the first system, each one of the resin ducts, which are numerically equal to the protoxylem strands of the radicle, is formed by vertical juxtaposition of two canals initiated partly in the hypocotyl and in the radicle. This system is closed at the level of the cotyledonary node. The second system consists of the anastomosis of the resin ducts initiated in the base of euphylls. This system is closed at the level of the base of the epicotyl and is not correlated with the first one. The primary resin ducts are formed on a schizolysigenous pattern. In the epicotylar bud, the schizogenous and lysigenous processes are described and they occur over a long distance. This schizolysigenous process of primary resin ducts is compared in young and adult plants. Key words: resin duct, ontogenesis, schizogeny, lysigeny, seedling, Pinus pinaster.
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