Arbuscular Mycorrhizal Fungi Enhance the Acquisition of Mineral Nutrients from Leaf Litter by Morella cerifera
Morella cerifera (L.) Small, the Wax Myrtle, forms both arbuscular mycorrhizas and cluster roots which generally are regarded as alternative adaptations for phosphorus acquisition. But whether or not arbuscular mycorrhizal fungi (AMF) provide any benefit to M. cerifera is not known. Nevertheless, AMF can proliferate extensively within the litter leaves that accumulate beneath M. cerifera. The main objective of this study was to determine if AMF are beneficial to M. cerifera host plants in the presence of leaf litter.
In the field, I examined leaf traits that affect the colonization of leaf litter by AMF. I compared AMF colonization of labile versus recalcitrant leaves, and that of leaf pieces with obstructed versus non-obstructed veins. In pot experiments, I examined if labile or recalcitrant litter influences the potential benefit of AMF to M. cerifera, and if nitrogen (N) or phosphorus (P) fertilization influences that benefit in the presence of recalcitrant leaf litter.
I found that AMF extensively colonize both labile and recalcitrant leaves, but that they colonize labile leaves more rapidly than recalcitrant leaves. I found significantly less colonization in leaf pieces with obstructed veins than in those with non-obstructed veins which suggests that penetration by the fungi primarily is mechanical and not enzymatic. The pot experiments showed that AMF are parasitic on M. cerifera except when recalcitrant leaf litter is present, and that the effects of AMF on M. cerifera are indirect and mediated through effects of AMF on N-fixing nodule dry weight. In both pot experiments, AMF enhanced litter decomposition and may have enhanced plant P-nutrition. AMF benefited M. cerifera growth in the absence of N fertilization but negatively affected M. cerifera growth when N was added. In the presence of litter, inoculation with AMF increased cluster root formation, suggesting that these two adaptations may be complementary in extremely nutrient-poor soils. Overall, this study shows that M. cerifera does benefit from association with AMF, and it suggests that AMF play a more important role in the acquisition of mineral nutrients from leaf litter than previously recognized.
Advisor:Dr. Bruce Schaffer; Dr. Leonel da Silveira Lobo Sternberg; Dr. Donald L. DeAngelis; Dr. David P. Janos
School:University of Miami
School Location:USA - Florida
Source Type:Master's Thesis
Keywords:biology arts sciences
Date of Publication:04/27/2008