NUTRITION IN PLANTS

NUTRITION IN PLANTS

·         Nutrients are essential components of food (like carbohydrates, proteins, fats, vitamins and minerals) which are necessary for living body.

·         Nutrients are important which enable living organisms to build their bodies, to grow, to repair damaged parts of their bodies, provide energy and provide the energy to carry out life processes.

·         Nutrition is the mode of taking food by an organism and its utilization by the body. Nutrition include nutrition requirement, taking of food by living organism and utilisation of taken food by body of living organism.

MODE OF NUTRITION IN PLANTS

·         Autotrophic (auto=self; trophos=nourishment) nutrition is the mode of nutrition in which organisms make food themselves from simple substances.

·         Only plants can prepare their own food by using raw materials like water, carbon dioxide(CO₂) and minerals. Therefore, plants are autotrophs.

·         Animals and most of other organisms are heterotrophs(heteros=others) i.e. they take in ready made food prepared by the plants.

PHOTOSYNTHESIS

·         Leaves are the food factories of plants i.e. photosynthesis(synthesis of food in plants) occurs in leaves. Photosynthesis also takes place in other green parts of plant like green stem and green branches-incase of desert plants whose leaves are spine-like(scale leaves) to reduce loss of water by transpiration.

·         To prepare food by plants in leaf, raw materials must reach leaf. Water and minerals present in soil are absorbed by the roots and transported to the leaves by continuous vessels (pipe like) which run throughout the root, stem, branches and leaves. Carbon dioxide (CO₂) from air is taken in through tiny pores surrounded by guard cells (called stomata) present on the leaf surface.

·         Chlorophyll (green pigment) present in leaves helps in capturing energy of sunlight. Absorbed/trapped energy is used to synthesise/prepare food using raw materials like Carbon dioxide (CO₂) and water(H₂O) along with release of Oxygen(O₂). This process of synthesizing food in presence of light is called photosynthesis (Photo: light, synthesis: to combine). Chlorophyll, sunlight, Carbon dioxide and water are necessary to carry out photosynthesis.

·         Sun is the ultimate source of energy for all living organisms.

·         In the absence of photosynthesis, there would not be life on earth i.e. no plants, least Oxygen, no food for herbivores and other animals.

·         During photosynthesis, chlorophyll containing cells of leaves in presence of sunlight use carbon dioxide and water to synthesise carbohydrates. The process can be represented as an equation:    

OxygenO₂ is released during the process. The carbohydrates are ultimately converted into starch. Presence of starch in leaves indicates the occurrence of photosynthesis. Starch is also a carbohydrate. Carbohydrates are made up of Carbon(C), Hydrogen (H) and Oxygen (O)

·         Algae can prepare their own food by photosynthesis. These are organisms seen as slimy, green patches in ponds or in other stagnant water.

SYNTHESIS OF PLANT FOOD OTHER THAN CARBOHYDRATES

·         Protein (Nitrogenous substance) and fats are other essential food for plants.

·         Plants can’t absorb abundant nitrogen from air. Certain soil bacteria convert gaseous nitrogen into usable form and release it into soil. These soluble Nitrogen forms are absorbed by the plants along with water and finally synthesise proteins and fats.

OTHER MODES OF NUTRITION IN PLANTS

·         Some plants are heterotrophs i.e. can’t synthesise their own food. Example; Cuscuta(Amerbel) doesn’t have chlorophyll and are yellowish tubular in structure which climb on a host plant for nutrients. It is a parasite as it deprives the host of valuable nutrients.

·         Insectivorous plants are insect-eating plants. Example; Pitcher plant whose leaf is modified in pitcher like structure and apex of leaf forms a lid which open and close the mouth of the pitcher. There are hairs directed downwards inside the pitcher. The lid closes and digest insect by the digestive juices secreted in the pitcher after entangling the insect into the hair.

SAPROTROPHS

·         Fungi secrete digestive juices on the dead and decaying matter and convert it into a solution from which is nutrients are absorbed. This mode of nutrition in which organisms take in nutrients in solution form from dead and decaying matter is called saprotrophic nutrition. Fungi also grow on pickles, leather, clothes, bread, etc left in hot and humid weather for long time.

·         Fungal spores are generally present in the air. Once they land on wet and warm things, they germinate and grow.

·         Plants which use saprotrophic mode of nutrition are called saprotrophs.

·         In symbiotic relationship, some organisms live together and share shelter and nutrients. Example; Certain fungi live in the roots of trees where tree provides nutrients to these fungi and plants in turn receives help in take up of water and nutrients from soil.

·         In organisms called lichens, a chlorophyll containing partner which is alga and a fungus live together. Fungus provides shelter, water and minerals to alga and in return alga provides food synthesised by photosynthesis.

HOW NUTRIENTS ARE REPLENISHED IN THE SOIL

·         Plant absorbs mineral nutrients from soil. Amount of these nutrients decline on continuous plantation of crops. Fertilizers and manures containing plants nutrients like nitrogen, potassium, phosphorous, etc are added from time to time to enrich the soil.

·         Plants need lots of nitrogen to make protein. Though nitrogen gas is available in plenty in the air, plants can’t use it in the manner they can use carbon dioxide. Plants can take only nitrogen in soluble form.

·         Rhizobium, a bacterium can take atmospheric nitrogen and convert it into soluble form. But, the bacterium can’t make its own food.  The bacterium gets shelter and food from leguminous plant root(gram, peas, moong beans). This association of plant root and bacterium is symbiotic relationship. This process helps farmers that they don’t need to add nitrogen fertilizer to soil.

·         Most plants are autotrophs. Only few plants adopt other modes of nutrition like parasitic and saprotrophic.