Palynology of the genera Modiola, Modiolastrum and Tropidococcus (Malvaceae)

Abstract

Pollen grains of seven species of three genera of Malvaceae are studied and described underoptical and scanning microscopy: Modiola: M. caroliniana (L.) G. Don, Modiolastrum: M.australe Krapov., M. gilliesii (Steud.) Krapov., M. lateritium (Hook.) Krapov., M. malviflorum(Griseb.) K. Schum., M. palustre (Ekman) Krapov. and Tropidococcus: T. pinnatipartitus (A.St.-Hil. & Naudin) Krapov. They show clear differences at generic level and it is also possible todistinguish species, which in some cases are based on less important phylogenetic pollencharacters. Pollen grains are sub oblate, oblate spheroidal and spheroidal; medium to bigsized. Surfaces do not show great variability; the seven species are echinate, withnanoverrucae or spinulae between spines. The apertures show variations in number (three totwelve) and distribution pattern: zonoaperturate, spiralloid arrangement and dizonoaperturate.The distinctive pollen of Tropidococcus pinnatipartitus (large sized, spheroidal, dizonoaperturate,number of apertures: twelve), supports its segregation from the genus Modiolastrum. A key todetermine these seven species is given. The basic chromosomes number of the three generawere compared with the apertures number, showing that those with lower basic chromosomesnumber, have fewer apertures than those with high ones. Five pollen grains types arerecognized based on the number and distribution pattern of apertures: 1) Type tricolporate:Modiolastrum malvifolium and M. palustre . 2) Type pentazonocolp(oid)orate: Modiolastrumaustrale y M.gilliesii. 3) Type pentacolp(oid)orate spiralloid arragement: M. lateritium. 4) Typehexacolp(oid)orado spiralloid arragement: Modiola caroliniana y 5) Typedizonocolp(oid)orate,arranged in series of six apertures at each side of the equator: Tropidococcus pinnatipartitus