Saprophytes

Rhizopus nigricans : This fungus is one of the black moulds. It is commonly known as the bread mould because of grows on moist, stale bread. It appears as a delicate black mass.

   The mycelium grows on the surface e and also inside the bread. The bread is known as the substrate. There are three types of hyphae:

• The stolons growing horizontally on the substrate

• The rhizoids or root like hyphae arising at points where the stolons come into contact with the substrate

• The sporangiophores bearing the sporangia which contain spores.

   The rhizoids branch and penetrate into the substrate. The tips of the rhizoids secrete enzymes such as amylases and proteases. These diffuse out of the hyphal walls into  the bread and bring about the extracellular digestion of carbohydrates and proteins to glucose and amino acids respectively. These soluble end products diffuse into the hyphal walls where they are assimilated into the cytoplasm.

    The thin walled highly branched mycelium of the rhizopus is well suited for this mode of feeding as it can penetrate into the substrate, as well as, provide a suitable large surface area for the absorption of the divested food.