The pin method, originally developed for the study of wood formation in temperate conifers, was applied in a study of secondary xylem development in woody vines growing in the tropical rainforest of Veracruz, Mexico.
Starting on April, 1993 the vascular cambium of eight different species, belonging to the Vitaceae, the Bignonaceae, and the Compositae, were marked with an entomological pin 0.67 mm in diametre. Five individuals of each species were used. The vascular cambium was marked on two opposite sites of the main stem, at the middle of an internode. Sixty days later, two more points were marked 90° apart from the first ones. The procedure was repeated every two months during one full year. A total of 24 points, arranged in two groups separated one meter in the same stem, were marked. Every pair of points were marked on the bark surface with paint of different color, to be able to identify them later for collection.
The marked vines were collected starting on August, 1994. The marked areas were isolated with a sharp blade, fixed with 2.5% glutaraldehyde, washed, dehydrated and infiltrated with plastic. Transverse sections 4 microns thick were stained with Toluidine Blue "O". Radial tiers of vessels produced after the marks were done, were counted under the microscope.
Preliminary results indicate that the four species of Vitaceae examined showed the faster rate of wood formation (46 cells/year), whereas the Bignonaceae showed the lowest (one cell/year).
Data on wood formation in tropical woody plants are very scarce in the literature, particularly for woody vines. Rates of wood formation provide very useful information for plant ecologists and forest managers. We plan to extend our research to other tropical woody species.
Key words: tropical woody vines, wood formation, pin method.
Correspondence: Guillermo Angeles, Universidad Nacional Autonoma de Mexico, Estacion de BiologiaTropical "Los Tuxtlas", Apdo. Postal 94, San Andres Tuxtla, Veracruz 95701, Mexico
Telefax: +52-294-30517