Morphology and structure of the pollen cone and pollen grain of the Araucaria species from Argentina

GEORGINA M. DEL FUEYO1, MARTA A CACCAVARI1,2 AND

BIOCELL

Año: 2008 p. 49 - 60

0327-9545

Abstract The pollen cone and the pollen grain of the two Argentinean species of Araucaria are described with LM, SEM and TEM. Primordia of pollen cones are formed in April-May and reach maturity by middle October in A. angustifolia (Bert.) O. Kuntze and by middle November in A. araucana. (Mol.) K. Koch. Characters of the mature pollen cones and microsporophylls between both taxa are clearly differentiated. Pollen grains are spheroidal-subspheroidal, inaperturate, asaccate with granulate exine and a subequatorial annular area which corresponds to the sexine thickness. Sculpturing consists of granules irregularly dispersed, sometimes fused to each other (A. angustifolia) or forming microrugulae (A. araucana). Microgranules and microspinules are also present. Pollen wall ultrastructure is formed by a granular ectexine and lamellated endexine. Granular elements in A. angustifolia are more loosely disposed forming more interstices and decrease in size more gradually towards the endexine than in A. araucana. Comparisons are made with pollen grains of other extant genera (Agathis, Wollemia) and also with fossil pollen (Araucariacites, Balmeiopsis, Cyclusphaera, Dilwynites) attributed to Araucariaceae contributing to the probable relationships within the family.