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Medientyp:
E-Artikel
Titel:
VENACION FOLIAR MENOR EN BYTTNERIA (STERCULIACEAE)
Beteiligte:
ARBO, MARIA M.
Erschienen:
Facultad de Ciencias Agrarias, 1977
Erschienen in:Bonplandia
Sprache:
Spanisch
ISSN:
0524-0476;
1853-8460
Entstehung:
Anmerkungen:
Beschreibung:
<p>This paper is the study of the minor foliar venation of 119 species of Byttneria genus. There are many published papers about minor venation, but very few consider a big number of species of the same genus. Apparently there is no data about Byttneria. However, the paper provides a historic account on dicots foliar minor venation. The analisis was done fundamentally on cleared adult foliage leaves, although leaf transections were utilized too. The following elements were taken into account: areoles shape and size; veinlets frequence, number and branching; bundle sheath structure; foliar sclerenchyma composition and topography; bundle sheath extensions; occurrence and type of cristals. There are two types of minor venation in Byttneria, named anisodictious and isodictious respectively. They are distinguished by the shape and size of areoles, and the frequence, number and branching of veinlets. Each type of minor venation is divided into four groups, according to the structure of the bundle sheath (parenchymatous, differenciated, intermediate) and the topography of the foliar sclerenchyma (mononeural, oligoneural, polineural, holoneural). The minor venation is analized in relation with the taxonomy of the genus. The species of Byttneria section show the same pattern: they have anisodictious venation with parenchymatous bundle sheath and holoneural sclerenchyma. Furthermore this section has certain exclusive characters as the possession of uniapertured nectaries, which contribute to separate it from the other sections. Vahihara is the section which has the greatest variability. Isodictious minor venation is present solely in a group of species of this section, as well as the differenciated bundle sheath. Urticifolia section has anisodictious minor venation, but offers extreme characters among its species with regard to the bundle sheath and foliar sclerenchyma. The study of the features which compose the minor venation in Byttneria led to the following observations: 1) anisodictious minor venation appears in all the sections of the genus while isodictious minor venation appears only in 35 of the 60 species of Vahihara. 2) Parenchymatous bundle sheath is common to all sections whereas the differenciated bundle sheath is present merely in a certain group of Vahihara. 3) The amount of sclerenchyma is quite variable, although a great number of species have holoneural sclerenchyma and very few species have mononeural sclerenchyma. According to these observations, the anisodictious venation pattern, with parenchymatous bundle sheath and oligoneural sclerenchyma is considered the most primitive of the genus (group 2). Starting from this pattern, 4 trends of specialization can be traced. The first leads to the pattern of group 1, through simplification of foliar sclerenchyma; the second leads to the pattern of subgroup 4, by the increase of sclerenchyma; the third, to the pattern of subgroup 4a, with the addition of a specialized bundle sheath. The last trend leads to the isodictious pattern of minor venation through a diminution of the areoles size and veinlets number and branching. This trend shows different levels of organization according to the bundle sheath type and sclerenchyma.</p>