Symbiotic Relationships Two important symbioses involve fungi: the mycorrhizae that occur on the roots of almost all vascular plants and the lichens that have evolved entirely different body forms from those of their symbionts. Mycorrhizae Fungi and the roots of almost all vascular plants form mutualistic associations called mycorrhizae (singular, mycorrhiza). The fungus gets its energy from the plant, and the plant acquires an efficient nutrient absorbing mechanism—the actively growing hyphae that penetrate regions of the soil untapped by root hairs. Phosphate uptake especially is increased when mycorrhizae are present. Two general types of mycorrhizae occur, differentiated by whether the hyphae live within the cortical cells of the roots or remain outside the cells: endomycorrhizae (endo = within; myco = fungus; rhizae = roots) and ectomycorrhizae (ecto = outside). Zygomycete taxa are components of most
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