Chapter 20, Problem 13STP

Summary Introduction

To write: The significance of sexual reproduction in Ascomycetes

Introduction: In the Kingdom Fungi belong some of the largest and oldest species on Earth. There is a honey fungus in eastern Oregon that is so large it's called the "Humongous Fungus." Many of the fungi are heterotrophic eukaryotes. They also described over 100,000 species of fungi.

Explanation of Solution

Ascomycete reproduction takes place when hyphae from opposite mating types fuse and one nucleus from each type pairs off in separate cells. The hyphae that continue to grow are septate. Each cell contains two haploid nuclei-one from each mating type. Eventually, the hyphae will develop a specialized reproductive structure called an ascocarp. Within the ascocarp, the haploid nuclei fuse to form a zygote. The zygote divides by meiosis, producing four haploid nuclei. These nuclei then divide by mitosis, forming a total of eight haploid nuclei. The nuclei develop into spores in the ascus, a saclike structure.

Conclusion

Spores produced by an ascus are called ascospores. When these spores are growing under favorable condition, each ascospore can develop into a haploid mycelium.