The ecology of AM fungi in fly-ash lagoons in Hong Kong.

CHAN, WING KUEN¹, BIN ZHAO² & XUEYING ZHUANG³.

¹Dept. of Applied biology & Chemical Technology, Hong Kong Polytechnic University, Hong Kong, CHINA.

The huge volume of fly-ash generated by the electricity plants in Hong Kong was deposited in lagoons and stabilized using sea water, rendering the habitat a highly stressed environment - high salinity, high pH, deficient in organic matter and nutrients for plant growth. The studied lagoon was almost barren when filled in 1992. In our recent survey, 24 species constituting 9 families of plants had been able to established naturally. Twenty of these species were found to be mycorrhizal, all except Zeuxine strateumatica (Orchidaceae) were infected by AM fungi. The infection rate varied from 12% to 100%.
The rhizospheric fly-ash samples were wet-sieved for evaluation of AM spores. The total spore count was low (~8 spores/g soil) compare to local forest soils (few hundred spores/g soil). However, large quantity of spores were observed inside the root segments. Four dominant types of spores isolated from the fly-ash samples were carefully described and maintained as pot cultures for further studies.
A pot experiment was conducted to test the infectivity and the effectiveness of the four types of AM spore isolated. Root infection (development of arbuscules and/or vesicles) was observed 2 weeks after inoculation. The infection rate had increased drastically in the second harvest (5 weeks). At this stage, young spores were formed in the pots. Growth of the host plants in the inoculated pots were significantly higher than those in the control pots. The results suggested that the tested fungal propagules have the potential to be applied in other similar stressed environments.