Q.Mention the steps involved in the sexual reproduction of Rhizopus.

Step 1. Which strains are needed. Rhizopus is mostly heterothallic, meaning sexual reproduction needs mycelia of two physiologically opposite (but visually identical) strains, conventionally labelled '+' and '-' (Rhizopus sexualis is the exception, being homothallic).

Step 2. Formation of the sex organs. Each of the two opposite mycelia first puts out a special hypha called a zygophore. The tips of two opposing zygophores swell to form progametangia; a septum then cuts off, near the tip of each progametangium, a terminal gametangium plus a small suspensor cell.

Step 3. Fusion of the gametangia. The two gametangia then fuse together. This fusion happens in two stages: plasmogamy (fusion of the cytoplasm/protoplasts of the two gametangia) followed by karyogamy (fusion of the nuclei). Because many nuclei of opposite strain are present, many pairs fuse, producing many diploid nuclei inside what becomes a single structure. …

List the sexual-reproduction sequence step by step: zygophore -> gametangia -> fusion - …

• Mixing up plasmogamy (cytoplasmic fusion) and karyogamy (nuclear fusion) or their order. …