Indistinct Growth Rings Research Articles

Seasonal Cambial Anatomy and Development of Xylem in Dalbergia sissoo Growing Under the Influence of Combined Air Pollutants

Seasonal behavior of vascular cambium and development of xylem were compared between the trees of Dalbergia sissoo growing under the influence of combined air pollutants (affected) and in relatively unpolluted area (normal). The duration of radial growth lasted for seven months in normal trees and five months in affected ones. In the normal trees, cambial cells began to divide in April with the sprouting of new leaves and ceased in November after reaching peak in August. The cambial cell division in affected trees started in June with the arrival of rains, reached peak in August and then ceased in November. Cell divisions in the cambium and development of xylem were suspended from December to March and December to May in normal and affected trees, respectively. Comparison between the length of fusiform cambial cells in normal and affected trees also showed significant variation. Xylem is diffuse porous with indistinct growth rings but it can be delineated by the presence of fine band of terminal parenchyma cells in trees of both localities. However, considerable variations occurred in the frequency and dimensions of xylem elements. Relatively more number of vessels with less lumen diameter was the characteristic feature of the xylem of trees growing under pollution stress. Similarly annual average length of xylem fibers was relatively less in the trees of pollution stress. Annual increment of xylem for two successive years was also found less in affected trees. Periodicity of cambium and xylem development is discussed in relation to the local climatic factors and phenology of the trees.

Wheeler, E.A. and Manchester, S.R. Woods of the Eocene nut beds flora, Clarno Formation, Oregon, USA. IAWA Journal, Supplement 3

Wheeler, E.A. and Manchester, S.R. Woods of the Eocene nut beds flora, Clarno Formation, Oregon, USA. IAWA Journal, Supplement 3

CAMBIAL VARIANT AND XYLEM STRUCTURE IN THE STEM OF COCCULUS HIRSUTUS (MENISPERMACEAE)

Development of cambial variant and xylem structure were studied in the stem of Cocculus hirsutus (Menispermaceae). In the early stages of stem development several collateral vascular bundles are joined by interfascicular cambium resulting in the formation of a complete cambial cylinder. After functioning for two to three years the cambial ring ceases its activity. Subsequently a second ring of cambium is formed from the innermost cortical parenchyma cells. These parenchyma cells undergo periclinal divisions to give rise to cells that become lignified, abaxially, and cambial cells, adaxially. The cambial cells divide periclinally giving rise to individual vascular bundles with xylem and phloem. Later the cambium in each bundle is joined by interfascicular cambium. Subsequent cambia develop similarly resulting in the formation of successive rings of xylem and phloem. During the leafless condition, all the cambial rings are dormant, and flanked by mature xylem and phloem elements. With the sprouting of new leaves, either the existing outermost cambium reactivates or an entire new ring of cambium develops. The xylem is diffuseporous with indistinct growth rings. It is composed of fibre-tracheids, tracheids, vessel elements, libriform fibres, and parenchyma cells. Xylem rays are multiseriate, compound and heterocellular. Deformed libriform fibres and vessel elements commonly occur among the ray cells in all the successive rings of xylem. The length of fibres and the height and width of xylem rays increase gradually from the centre towards the periphery of the stem.

GROWTH RINGS AND TREE GROWTH IN YOUNG PARA RUBBER TREES FROM PENINSULAR MALAYSIA

As part of a study of growth ring structure and growth periodicity in tropical trees, the formation of indistinct growth rings in young Hevea brasiliensis cultivated in Peninsular Malaysia was investigated. The cycle of shoot elongation included the following stages: apical growth (three phases), leaf maturation (two phases), and radial growth with no change in appearance (one phase). Correlation analysis of height and radial increment revealed a 6-week cycle and a 4- to 5-week delay between the height increment and the radial increment. The darker bands visible on wood disks had radially flattened wood fibres and characteristic vessels in radial multiples. It is suggested that the darker bands include growth ring boundaries, but with quite different radial variation of fibre thickness than in growth ring boundaries of temperate trees.

Agaristoxylon garennicum Gerrienne et al., gen. et sp. nov., an arborescent Ericaceae from the Belgian Upper Paleocene: palaeoenvironmental implications

This paper describes a silicified trunk fragment, Agaristoxylon garennicum Gerrienne et al., gen. et sp. nov., collected from a new locality at Péruwelz (Belgium) in the marine Thanetian (Upper Paleocene), and discusses the fossilisation conditions of the specimen. The anatomical structure of Agaristoxylon is similar to that of the modern ericaceous genus Agarista ( Agauria), encountered in the tropical and subtropical North and South America, and in the tropical regions of Africa, Madagascar and the Mascarene Islands. Together with other palaeontological data, the presence of Agaristoxylon supports the hypothesis that a climate of subtropical type with high atmospheric humidity could have prevailed in Belgium, at least locally, during the Late Paleocene. The occurrence of indistinct growth rings suggests the existence of seasonal drier periods.

Wood anatomy of the dicotyledons indigenous to New Zealand 7. Santalaceae

Abstract Anatomical features of the secondary xylem of Mida salicifolia A. Cunn. and Exocarpus bidwillii Hook.f. are described. These woods are diffuse-porous with slightly distinct to indistinct growth rings. The vessels are mostly solitary in E. bidwillii but in M. salicifolia they also occur in radial multiples. Vessels have simple perforation plates with sparse scalariform plates in M. salicifolia. Fine spiral thickening is occasionally present in vessel tails of E. bidwillii. An unusual thickening associated with bordered pits on tangential and radial walls of vessels is found in E. bidwillii. Pits on vessel walls are scattered in E. bidwillii but in M. salicifolia they are compactly arranged in opposite to alternate pattern. Vessel pits to rays are mostly bordered with some simple to almost simple pits. Some vessel pits to rays are large and have irregular shape. Axial parenchyma, which is mainly apotracheal, is moderately frequent to abundant. Poorly developed boundary parenchyma is sometimes prese...

Wood anatomy of the dicotyledons indigenous to New Zealand

Anatomy of the secondary xylem of Quintinia acutifotla Kirk, Q. serrata A. Cunn., Ixerba brexioides A. Cunn., and Carpodetus serratus J.R. et G. Forst. is described. These woods are diffuse-porous with distinct to indistinct growth rings. The vessels are mostly solitary, angular, and have exclusively scalariform perforation plates with approximately 20 to 140 bars. Intervascular pits when present are opposite and scalariform. Fine spiral thickening is present in vessels and fibrc-tracheids of C. serratus. In all the indigenous species the vessel pits to rays are bordered, round and radially elongated. Axial parenchyma which is moderately frequent is diffuse, diffuse-in-aggrcgates, scanty paratrachcal, and rarely vasicentne. Rays are mostly heterogeneous type II. Uniscriate rays arc more numerous than the multiseriatcs. In C. serratus rhomboidal crystals arc present in the ray parenchyma. The fibrous tissue in all the species is composed of non-septate fibre-tracheids. Anatomical differences betwe...