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Vegetative Development, Primary and Secondary Growth of the Shoot System of Young Terminalia Superba Tropical Trees, in a Natural Environment

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Vegetative Development, Primary and Secondary Growth of the Shoot System of Young Terminalia Superba Tropical Trees, in a Natural Environment Vegetative development, primary and secondary growth of the shoot system of young Terminalia superba tropical trees, in a natural environment. I. Spatial variation in structure and size of axes E de Faÿ To cite this version: E de Faÿ. Vegetative development, primary and secondary growth of the shoot system of young Terminalia superba tropical trees, in a natural environment. I. Spatial variation in structure and size of axes. Annales des sciences forestières, INRA/EDP Sciences, 1992, 49 (4), pp.389-402. hal-00882811 HAL Id: hal-00882811 https://hal.archives-ouvertes.fr/hal-00882811 Submitted on 1 Jan 1992 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Original article Vegetative development, primary and secondary growth of the shoot system of young Terminalia superba tropical trees, in a natural environment. I. Spatial variation in structure and size of axes E de Faÿ Université de Nancy I, Laboratoire de biologie des Ligneux, BP 239, 54506 Vandœuvre-lès-Nancy Cedex, France (Received 21 August 1991; accepted 17 April 1992) Summary — Spatial variations in trunk structure including wood histology and size of axes were ex- amined in 5 21-month-old Terminalia superba Engl and Diels trees, grown in a natural tropical envi- ronment. Long and shorter internode series alternated along the main axes, forming rather poorly delimited units of extension. In trunk wood, the paratracheal axial parenchyma of the confluent type formed irregular bands, the spacing of which varied gradually, increasing and decreasing alternately. These widely- and narrowly- spaced parenchyma bands differentiated various wood layers. The radi- al enlargement and wall thickness of fibres also varied in the same manner, as did, but to a lesser extent, the width of parenchymal bands, the radial enlargement of parenchyma cells and vessels, and the wall thickness of vessels. The number of various wood layers in trunk segments that were defined by variations in intemodal length was not related to the order of appearance of the trunk seg- ments in question. These results suggest that trunk wood exhibited alternating dense and not very dense wood layers, but they did not provide visible structural evidence of a well-pronounced growth periodicity in the main shoot of Terminalia superba. The existence of a structural discontinuity in the peripheral wood and the significance of the basipetal differentiation of the outermost adjacent wood layer have been discussed in relation to seasonal changes in climate and phenology. On the other hand, trunk thickness increased markedly from 5 cm above to 5 cm beneath the upper pseudo- whorls of branches. The thickness of axes (branches and trunks) was closely related to the number of sympodial units located in a centrifugal and an upper position respectively. Moreover, a pseudo- whorl of branches was generally inserted in the middle part of trunk segments defined by variations in internodal length. These data indicate trunk-branch correlations. It is suggested that some struc- tural variations in trunk wood could be related to branching. radial size / structural unit / Terminalia superba / tropical tree / wood Résumé — Développement végétatif, croissance primaire et secondaire du système cauli- naire de jeunes arbres tropicaux de l’espèce Terminalia superba, dans un environnement na- turel. I. Variation dans l’espace de la structure et de la dimension des axes. Les variations dans l’espace de la structure du tronc - y compris l’histologie du bois - et de la dimension des axes furent examinées chez 5 plants de Terminalia superba Engl et Diels âgés de 21 mois et poussant dans un environnement naturel tropical. Des séries d’entre-nœuds longs et plus courts alternaient le long des axes principaux formant des unités de croissance mal délimitées. Dans le bois des troncs, le paren- chyme axial paratrachéal, de type confluent, formait des bandes irrégulières dont l’espacement variait graduellement, augmentant et diminuant en alternance. Ces bandes de parenchyme largement et fai- blement espacées différenciaient des couches de bois. La dilatation radiale et l’épaisseur des parois des fibres variaient aussi de la même manière que précédemment. Il en était de même, quoique à un moindre degré, de l’épaisseur des bandes de parenchyme, de la dilatation radiale des cellules paren- chymateuses et des vaisseaux, et de l’épaisseur des parois des vaisseaux. Le nombre de couches de bois dans les segments de tronc définis par des variations dans la longueur des entre-nœuds n’était pas lié à l’ordre d’apparition des segments en question. Tous ces résultats suggèrent que le bois des troncs présentait des couches alternativement denses et peu denses, mais ils ne donnent pas de preuve structurale d’une périodicité de croissance bien marquée dans la flèche des Terminalia superba. L’existence d’une discontinuité structurale dans le bois périphérique et la signification de la couche de bois adjacente la plus externe sont discutées en relation avec les changements de saison et de phénologie. Par ailleurs, l’épaisseur des troncs s’accroissait de façon marquée de 5 cm au- dessus à 5 cm en-dessous des étages supérieurs de branches. L’épaisseur des axes (branches et troncs) était étroitement liée au nombre d’unités sympodiales en position respectivement centrifuge et supérieure. De plus, un étage de branches était généralement inséré dans la partie médiane des seg- ments de tronc définis par des variations dans la longueur des entre-nœuds. Ces données attirent l’attention sur les corrélations entre branches et tronc. II est suggéré que des variations structurales dans le bois du tronc pourraient être liées à la ramification. dimension radiale / unité structurale /Terminalia superba / arbre tropical / bois INTRODUCTION cambial growth among the trees of the inter- tropical zone. However, detailed studies on Some attention has been paid to growth cambial activity, such as histophysiological phenomena in tropical trees. Morphological investigations are still rare, fragmentary and concern mature trees in- and morphogenetic studies on shoot growth generally growing have demonstrated the basic knowledge of termittently, the wood of which displays an- nual Paliwal and continuous and flushing - or rhythmic - growth rings (Lowe, 1968; growth and architectural models (Bond, Prasad, 1970; Lawton and Lawton, 1971; 1942; 1945; Scarrone, 1965; Hallé and Rao, 1972; Amobi, 1973; Paliwal et al, Martin, 1968; Borchert, 1969; Hallé and 1976; Ghouse and Shamima Hashmi, 1979; Oldeman, 1970; Greathouse et al, 1971; Zamski, 1979; Rao and Dave, 1981; Rog- Vogel, 1975a,b; Hallé et al, 1978; Ng, 1979; ers, 1981; Dave and Rao, 1982; Desh- Parisot, 1988; El-Morsy and Millet, 1989). pande and Rajendrababu, 1985; Venugopal Concerning secondary growth, there is and Krishnamurthy, 1987). As regards cor- relations between re- some information on wood production and growing organs, only between leaf and shoot on the existence, anatomy and periodicity lationships growth have been examined in a few trees of growth rings in the wood of numerous tropical species (Hummel, 1946; Mariaux, 1967; (Greathouse et al, 1971; Prévost, 1972; Lowe, 1968; Mariaux, 1969, 1970; Gill, Borchert, 1973, 1978) and the effect of 1971; Amobi, 1974; Détienne et Mariaux, leaves on internode elongation has been 1975, 1976, 1977; Fahn et al, 1981; Mari- demonstrated in Terminalia superba (Mail- lard aux, 1981; Zamski, 1981; Ash, 1983a, b; de et al, 1987b). Faÿ, 1985; Boninsegna et al, 1989; Dé- Young plants of the African species Ter- tienne, 1989; Jacoby, 1989; Worbes, 1989). minalia superba Engl and Diels grown in a These data suggest various patterns of natural environment were studied within the context of research on growth rhythms MATERIALS AND METHODS and relationships between primary and of the shoot T secondary growths system. The trees studied came from the experimental superba is a forest species, the architec- plantation of the Centre Technique Forestier ture of which has been characterized by Tropical on the Ivory Coast, located in the forest Hallé and Oldeman (1970) as Aubréville’s of Anguédédou, about 30 km north-west of Abid- model. Its trunk is a monopode, the growth jan. A clonal plot was put at the author’s dispo- of which is assumed to be rhythmic and sal to study 5 trees. The trees were descended from stem cuttings that had been made from 3- branches a gives pseudowhorled arrange- month-old shoots and had been planted 3 called a tier. Branches ment, commonly months later. They were aged 21 months when are sympodial and horizontal by apposition studied. A good size, well-separated tiers of to spiral phyllotaxy units. Each sympodial branches and an absence of any trunk reitera- unit is characteristic of the genus Terminal- tion were the criteria for the choice of plants. ia, the Terminalia branching being specifi- The clonal origin was unknown at the time of se- lection, which should have ensured a certain cally described in T catappa (Hallé and variability among the chosen trees, as if seed- Oldeman, 1970; Tomlinson and Gill, 1973; lings had been studied. The 5 trees (TA-TE) Fisher, 1978). The vegetative development were of the same geographic provenance, 2 of T superba, at an early stage, has recent- were half-sibs (TA and TC) and 2 were of the ly been studied under controlled conditions same clone (TD and TE). The ground had been (Maillard, 1987; Maillard et al, 1987a,b; prepared, before planting, by manual cutting of the forest the was 2.5 1989).
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