Mycorrhizal roles in broomsedge plants under phosphorus limitation and aluminum toxicity.

摘要

This dissertation examined roles of arbuscular mycorrhizal fungi, of which Glomus clarum is the primary species, in broomsedge (Andropogon virginicus) plants under limited Pi and elevated Al conditions in four studies. The inoculum originated from an acidic coal-mining site in Morgantown, WV. The inoculum of Glomus clarum from INVAM collection, which originated from an alkaline coal-mining site in WV, was also used in two of the studies. Plants were grown in an acid-washed sand culture system with a modified Hoagland's nutrient solution in a growth chamber.; Mycorrhizal fungal colonization pronouncedly enhanced growth of broomsedge plants under limited Pi and/or elevated Al conditions. Under Pi limiting conditions, mycorrhizal broomsedge plants made more investment on roots, drew down solution Pi concentrations to lower level, all of which leads to increasing exploited Pi pool, and increased phosphorus use efficiency. Moreover, mycorrhizal plants balanced accumulation of nutrients under varying Pi availability. All these brought about by mycorrhizal symbioses benefit broomsedge plants overcoming Pi deficiency and supporting optimal growth of host plants under limited Pi availability.; Broomsedge plants do not have an inherent mechanism to block Al influx and tolerate Al toxicity. Mycorrhizal association with AM fungi significantly conferred Al resistance in broomsedge plants by facilitating Pi uptake in the early stages, reducing Al influx, suppressing Al translocation within plants, altering profiles of organic acids, releasing a great amount of organic acids, and improving nutrition of host plants. However, different fungal isolates had differential effects on Pi acquisition, Al influx and translocation, nutrient uptake, and exudation of organic acids as Al concentrations changed. These differences may be associated with the differential adaptations of these two AM fungal strains to their original habitats.; Moreover, two AM fungal isolates differentially altered physiology of host plants under different Pi and Al levels, such as stomatal conductance, photosynthesis, leaf respiration, root protein, and root acid phosphatase examined in this study. These adjustments of physiological traits might be related to other changes of plants that support sustainable growth of host broomsedge plants.; Therefore, broomsedge plants rely on AM fungi to grow and establish in adverse habitats.