The infection of pollen by zoosporic fungi in tropical soils and its impact on pollen preservation: A preliminary study
Phuphumirat, Wongkot; Gleason, Frank H.; Phongpaichit, Souwalak; Mildenhall, Dallas C.
Zoosporic true fungi (sometimes called chytrids) are important agents responsible for deterioration of pollen in tropical soil. To have more understanding of the role of zoosporic fungi as a pollen decomposer, the degree of infection of pollen from nine plant species by zoosporic fungi in three types of soil (loamy soil composed mainly of decaying leaves, swamp clay, and sandy soil) was examined using a pollen-baited culture method. A total of 243 surface soil samples were collected from the three study sites in August, October, and December 2007. Environmental parameters in soil, i.e. pH, Eh, and organic matter, were measured to study their effects on the degree of fungal infection of pollen. The results showed that chytrids were the predominant taxa infecting all pollen species in all soil types. Soils rich in organic matter with low pH and high Eh values provide appropriate conditions for fungal growth as the highest percentage of fungal infection was found in loamy soil samples. In this study, the large pollen with a thin exine wall and an extensive pollen aperture tended to be most infected. These types of pollen grains allowed the rhizoids and hyphae of chytrids to penetrate into the pollen grains easily in order to access the large supply of food resources. However, further studies are needed to provide a better insight into the processes of degradation of pollen.