The Growth of Mushrooms

Fungi Characteristics

• A mushroom’s defining characteristic is the way it gets food. Members of the Fungi Kingdom are nonmotile and heterotrophs, they get food and energy from other organisms. Fungi secrete a digestive enzyme that breaks down organic material around it then absorbs the resulting nutrients. Some fungi are decomposers, retrieving their food from dead material. Some fungi are parasites, living off living organisms. Unlike plants, fungi are nonvascular, meaning they have no internal tissues transporting nutrients. Fungi cell walls are comprised of chitin, the component found in insect coverings.

Major Groups of Fungi

• Fungi are categorized into three groups: ascomycetes, basidomycetes and zygomycetes. Ascomycetes are sac fungi, reproducing with spores inside sacs. Truffles and penicillins are examples of ascomycete fungi. Basidomycetes are the most common type of mushroom. Examples of basidomycetes fungi include club fungi, rusts and corm smut. The club fungi are merely the aboveground fruiting body, with the bulk of the organism underground. One example is a 2,200-acre mass in Oregon that is 3 feet deep and 2,400 years old. Zygomycetes are named because they form a diploid spore, like a zygote. Examples of zygomycete fungi include bread mold and mycchorryzaae, a beneficial fungus found on plant roots.

Mushroom Life Cycle

• The mushroom’s life cycle begins with the spore. Spores are released from the fruiting body. The spores germinate, and form a single nucleus structure, or haploid, called a hyphae. These haploid hyphae meet and form a dikaryon or two nuclei per cell structure. The mushroom continues growth and sends up fruiting bodies. Some of the nuclei fuse in the cells, creating a diploid, a cell containing two sets of chromosomes, nucleus. This diploid nucleus undergoes meiosis, cell division where half of the chromosomes are in each division, resulting in new haploid cells. These new haploid cells turn into spores, which blow away and begin the process all over again.

Asexual vs. Sexual Reproduction

• Asexual reproduction is a type of reproduction involving only one parent that produces genetically identical offspring by division of a single cell or the entire organism into two or more parts. Many plants reproduce asexually through division and other propagation means. A single mushroom can reproduce this way through single cell division. Sexual reproduction in mushrooms is called plasmogamy, the haploid nucleus of a donor cell penetrates the cytoplasm of a recipient cell.