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www.GOALias.blogspot.comBoojho says once hisgrandfather told him that hiswheat fields were spoiled by afungus. He wants to know iffungi cause diseases also.Paheli told him that many fungilike yeast and mushrooms areuseful, but some fungicause diseases in plants,animals and humans.Some fungi are also usedin medicines.During the rainy season they spoil manythings. Ask your parents about themenace of fungi in your house.The fungal spores are generallypresent in the air. When they land onwet and warm things they germinateand grow. Now, can you figure out howwe can protect our things from gettingspoiled?Some organisms live together andshare shelter and nutrients. This iscalled symbiotic relationship. Forexample, certain fungi live in the rootsof trees. The tree provides nutrients tothe fungus and, in return, receives helpfrom it to take up water and nutrientsfrom the soil. This association is veryimportant for the tree.In organisms called lichens, achlorophyll-containing partner, which isan alga, and a fungus live together. Thefungus provides shelter, water andminerals to the alga and, in return, thealga provides food which it prepares byphotosynthesis.1.51.5 HOWNUTRIENTSAREREPLENISHEDIN THE SOILHave you seen farmers spreadingmanure or fertilisers in the fields, orgardeners using them in lawns or inpots? Do you know why they are addedto the soil?You learnt that plants absorbmineral nutrients from the soil. So, theiramounts in the soil keep on declining.Fertilisers and manures contain plantnutrients such as nitrogen, potassium,phosphorous, etc. These nutrients needto be added from time to time to enrichthe soil. We can grow plants and keepthem healthy if we can find out thenutrient requirement of plants.Usually crops require a lot of nitrogento make proteins. After the harvest, thesoil becomes deficient in nitrogen.Though nitrogen gas is available inplenty in the air, plants cannot use it inthe manner they can use carbon dioxide.They need nitrogen in a soluble form.The bacterium called Rhizobium cantake atmospheric nitrogen and convertit into a soluble form. But Rhizobiumcannot make its own food. So it lives inthe roots of gram, peas, moong beansand other legumes and provides themwith nitrogen. Most of the pulses (dals)are obtained from leguminous plants.In return, the plants provide food andshelter to the bacteria. They have aNUTRITIONIN PLANTS7