Symbiosis is a type of interaction of two living organisms where both the associated partners derive some benefit from each other both co-exist and flourish well.
Mycorrhiza is a symbiotic association between fungus and the roots of vascular plants. The fungus colonizes the roots of the host either intra or inter cellularly. It helps in the nutrient absorption from soil for the plant. Mycorrhizal associations are present in conifers, i.e., Pinus, Cedrus, Abies and Picea.
Coralloid roots develop in Cycas. It is produced in clusters at the base of the stem and protrudes out on the ground. It dichotomously branched and greenish in colour. It contains algal zone in cortex. This algal zone contains blue green algae like Anabaena and Nostoc which grow in symbiotic association with coralloid roots.