XVI International Botanical Congess

The ultrastructure of the apertural intine in pollen grains of the tribe Euphorbieae has been studied. The apertural intine presents a characteristic structure with thickenings running along both sides of the colpus. Arrangement of these intinous thickenings depends on the distance from the ora. This special morphology of the intine is found in all taxa studied here. In an effort to determine the nature and role of this intine, pollen grains of Euphorbia peplus were germinated in vitro and several monoclonal antibodies against pectins (JIM5 and JIM7) were applied to localise these epitopes on such structure. Our results show that this characteristic structure suffers an elongation and disorganisation, as well as an important labelling for pectins. The tribe Euphorbieae is considered to be the most evolved taxon of the family, so these features may represent an apertural mechanism well adapted to harmomegathic changes, and thus making easy the germination process.