Q)Give a comprehensive account of the structure and life history of Myxomycetes.
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Answer:
The myxomycete life cycle is reviewed and evaluated based on historic and current evidence, and completely illustrated in detail, including trophic stages (myxamoebae, swarm cells, and plasmodia), resting or dormant stages (spores, microcysts, and sclerotia), and developing fruiting bodies. Most books and journal papers fail to include all life cycle stages or accurately illustrate the morphology and mating of swarm cells. Life history strategies of the corticolous myxomycetes, as related to type of plasmodium and fruiting body, are described and quantified based on the five taxonomic orders. The bark of 30 individual trees, representing six different species, and 30 grapevines of two species, was sampled from the canopy at 3.3 m to 16.5 m in the Berea College Forest and Daniel Boone National Forest in Kentucky and in the Great Smoky Mountains National Park in Tennessee, using the double-rope climbing technique. Moist chamber cultures of bark samples (580) yielded a total of 46 myxomycete species, representing 20 genera, with 4 taxa identified only to genus. Results showed that each taxonomic order is well represented and the majority of corticolous myxomycetes have stalked fruiting bodies and the proto- or trichiaceous plasmodial type. This evidence supports observations that corticolous myxomycetes in the tree canopy are r-selected species, adapted to irregular wet and prolonged dry cycles on the bark surface of living trees and vines by utilizing the resistant, dormant, resting stages of the life cycle. The most abundant corticolous species utilize the plasmodial type with the smallest surface to volume ratio (protoplasmodium), sporulate quickly within 2 to 4 days by producing a single, tiny, stalked sporangium, and efficiently release spores via an evanescent peridium. Species in the order Echinosteliales are the best examples of this life history strategy.