PATTERN OF POLLEN COMPOSITION OF OLIGOELE MENTS, POTENTIAL MARKER IN PLANT CLADISTICS

In botany tentative attempts have been made to classify species, based not on the plant as a whole, but on a particular character, for examp le pollen characteristics. Pollen, which is involved in the transmissi on of male genetic information during sexual reproduction, is of parti cular interest in distinguishing plants and their relationships. These characters, observed in photon- and scanning electron- microscopy are symmetry, form, number and position of germinating areas. Being genet ically stable for a given species, they identify a plant. Recently, a novel character has been added: the concentration of elements in the e xine, determined by electron probe micro-X-ray analysis. It is interes ting to follow relationship of plant species, based on the mineral com position of their pollen as a whole, taking into account both plastic and oligoelements, obtained via an inductive coupled plasma spectromet er. Samples of pollen from different plant species, at distinct taxono mic levels, were analyzed; the results were submitted to a normalisati on procedure and the standard patterns obtained were investigated by m eans of a number of numerical techniques (clustering and factor analys is). The aim was to establish if elements could be considered as chemi cal markers in plant cladistics. The mineral composition in a given sp ecies appeared quite stable and this furnished a convenient identifica tion-critorion. This approach further allows a chemo-taxonomy of speci es, in as much as organization of families, and perhaps orders, would conform to the phylogenetic proximity-criterion. Hence, we found clust ers including pollen of Gramineae, Coniferae, Betulaceae.... This meth odology, that should be completed and corroborated on a wider range of samples would provide an original responsee to the problems of identi fication and classification encountered in a pollen bank. It follows t hat: the pattern of pollen composition of oligo-elements, calcium and magnesium is a marker in plant cladistics. Since a typology depending on proximity is found between plant species, families and orders. an u nknown pollen sample may be located, tentatively, on the base of a des cribed model of pollen relation (shortest connexion network - Prim alg orithm - and pollen of Bactris-oil palm and Phoenix dactylifera). Henc e, the working hypothesis that the chemical markers and, in particular , oligo-elements, complete pollen typologies based on morphological an d structural characters, appears quite reasonable. In conclusion, this paper brings a complement to the mineral composition of the exine.