Pollen presenters in the South African flora

In contrast with the majority of flowering plants, where pollen is released directly from the anthers to travel to the female organ to effect fertilization, the pollen in certain species belonging to fifteen families worldwide is initially deposited on the female part of the flower before transport to another flower occurs. The structure on which the pollen is deposited is (in almost all cases) a modification of the style called the pollen presenter. In South Africa, pollen presenters are ubiquitous in the Asteraceae, Campanulaceae, Lobeliaceae, Goodeniaceae and Proteaceae; they also occur in almost half of the genera in the Rubiaceae, and in Polygala and some Muraltia (Polygalaceae), in Turraea, Trichilia and Ekebergia (Meliaceae) and a small proportion of taxa in the Fabaceae. The modifications of the style take various forms and can be summarized into actively and passively operating types. The active forms act like a piston to push the pollen away from the anthers, while the passive forms are static, receiving the pollen from the anthers before the anthers fall away to leave the pollen ready to be removed from the presenter by animals or the wind. In the past, pollen presenters have either not been recognized or have been described as styles or stigmas. This leads to confusion about processes involved in pollination and wastes useful information which is of value in taxonomic studies. In teenstelling met die meeste blomplante waar stuifmeel direk vanaf die helmknoppe vrygestel word om na die vroulike orgaan versprei te word en bevrugting te bewerkstellig, word die stuifmeel van sommige spesies van vyftien families wêreldwyd eers op die vroulike deel van die blom gestort voordat dit na ’n ander blom vervoer word. Die struktuur waarop die stuifmeel gestort word, is (in byna alle gevalle) ’n wysiging van die styl en word ’n stuifmeelaanbieder genoem. In Suid-Afrika kom stuifmeelaanbieders algemeen voor by die Asteraceae, Campanulaceae, Lobeliaceae, Goodeniaceae en Proteaceae; hulle word ook aangetref by byna die helfte van die genusse van die Rubiaceae, en by Polygala en sommige Muraltia spesies (Polygalaceae), by Turraea, Trichilia en Ekebergia (Meliaceae) en by ’n klein aantal taksons in die Fabaceae. Die wysigings van die styl neem verskeie vorms aan en kan in aktiewe en passiewe tipes ingedeel word. Die aktiewe vorms werk soos ’n suier en stoot die stuifmeel weg van die helmknoppe, terwyl die passiewe vorms staties is en die stuifmeel van die helmknop