Certain plants like mushrooms lack the presence of chlorophyll pigment and also do not depend on other animals for food. Mushrooms have a different mode of nutrition and hence belong to a different class of plants, known as fungi. Fungi require a humid environment to grow. Mushrooms are saprotrophs, which obtain nutrients from the dead and decaying matter by secreting digestive juices outside their own cells.
These juices mix with the dead and decaying matter and form a solution which is taken up as a source of nutrients by saprotrophs. Since saprotrophs depend on the external food source, they are considered to be a type of heterotrophic nutrition. We can observe fungi on leather items during monsoon days, on leftover bread etc.
Some plants live in a symbiotic relationship with other plants. In a symbiotic relationship, fungus growing on the trees derives nutrients and shelter from the tree and in return help the tree in conducting water and minerals. In this symbiotic relationship, both the trees and fungus make benefits from each other.
A very common example of the symbiotic relationship is that of fungus and alga. Alga contains chlorophyll by which it prepares food and provides minerals to fungus, and fungus in return provides shelter, water, and minerals to alga.
Replenishing of nutrients in the soil:
Nutrients in the soil keep depleting from time to time. It can be replenished in various ways to maintain the continuous growth and development of the plant.
The addition of vermicomposts, manures, and fertilizers rich in nitrogen, phosphorus and potassium to the soil time to time results in high yield of the crop. Also, fixation of atmospheric nitrogen in the soil can be increased by cultivating leguminous plants, so as to increase the reproduction rate of rhizobium bacteria which helps in nitrogen fixation process.
These bacteria are in symbiotic relationship with leguminous plants, as they provide nitrogen fixation into the soil in return for which they derive nutrients from the roots of these plants.