Friday 28 September 2012

Nutrition In Plants

 





What is Nutrition??

THE PROCESS OF TAKING IN FOOD BY AN ORGANISM AND IT'S UTILIZATION BY THE BODY IS CALLED NUTRITION.










Autotrophic Nutrition

The term autotroph has been derived from two Greek wards-auto means self and troph means nutrition. In this mode of nutrition, the organisms prepare their own food from simple raw materials like water, carbon dioxide and mineral salts in the presence of sunlight. Chlorophylls present in the chloroplast or green plants are the site of food production. Accordingly all green plants are the examples of this category. The process by which they synthesize food is known as photosynthesis.
The cells of green leaves and young stems contain  numerous green structures called chloroplasts.The chloroplasts are green in colour  because of the presence of a  green pigment called chlorophyll.  It is chlorophyll that traps energy from  Sunlight.Leaves take in Carbon dioxide from the air through tiny pores called stomata (singular = stoma) mostly present on the underside of the leaves.The pore is bordered by a pair of specialized cells known as guard cells that are responsible for regulating the size of the opening. 

The water and minerals are absorbed from the soil by root hairs present on the roots.The water and minerals absorbed by the plants are transported to leaves by xylem vessels that are like pipes . These pipes run through the root, stem, branches and leaves.

Photosynthesis

Photosynthesis (photo=light synthesis=combination of components) is a process used by plants and other organisms to convert the light energy captured from the sun into chemical energy that can be used to fuel the organism's activities.


Photosynthesis uses carbon dioxide and water, releasing oxygen as a waste product.

Carbon dioxide + Water + Light energy → Glucose + Oxygen

Synthesis of food other than carbohydrates by plants

Carbohydrates that plants synthesize during photosynthesis are made up of carbon,hydrogen and oxygen.  These are used to synthesize other components of food such as proteins and fats.Proteins contain nitrogen. Though, air contains large amounts of nitrogen ,plants cannot absorb this nitrogen directly.They get nitrogen in two ways.

  • Soil contains certain bacteria in soil called Rhizobium that can convert atmospheric nitrogen into water soluble compounds.Plants absorb these compounds along with water to get nitrogen.  (Rhizobium cannot make its own food.It therefore lives in the roots of leguminous plants like gram,peas and other pulses, where it gets food and shelter. In turn ,it provides them with nitrogen .It thus,has a symbiotic relationship (scroll down) with leguminous plants).
  • Farmers add fertilizers rich in nitrogen to the soil.These are absorbed by plants.

Phototrophic and  Chemoautotrophic Nutrition 
Some nongreen becteria like sulphur bacteria can use energy which they derive from some chemical reactions occurring in them. With this energy they manufacture their food. This process is called chemosynthesis. Thus the autotrophs include both the photosynthetic and chemosynthetic organisms.

Heterotrophic Nutrition

The word heterotrophy has been derived from two Greek words-hetero means different and troph refers to nutrition of food. The organisms which derive their food from others are known as heterotrophic organisms. They depend for their food on other organisms, hence they are called consumers. All animals, human beings and non-green plans like fungi come under this category. They consume complex organic food prepared by autotrophs or producers and break it into simple from to derive nourishment. 

Heterotrophs may be parasitic partial and total), saprophytic ,symbiotic and insectivorous.

1. Parasitic:
The term has been derived from two Greek works: Para means feeding and sites means grains. Parasitic organisms are those which live on or inside other living organisms to derive their food. Such a mode of nutrition is known as parasitic nutrition. A parasite derives its food (nutrition) from the host in different ways the mode of feeding depends upon its habit, habitat, and modifications.
  • Total

Parasitic plants have special suckers that may invade the host plant’s food channels and draw off sugars and minerals. Total  parasitic plants are totally dependent on their host for food .
Example: Total stem parasite like cuscuta and root like orobanche are never green and consequently they have no power to prepare their own food. They get all their food supply from the host plants.


  • Partial

A partial parasite has green leaves and thus is capable of manufacturing food, but is dependent on host plant for water supply.


 

2. Saprophytic:
The word saprophyte has been derived from the Greek words sapro meaning rotten and phyto meaning plants. Saprophytic organisms derive their food from decomposing dead organisms.

3.Insectivorous
They are said to be partly autotrophic and partly heterotrophic. These autotrophs supplement their nutritional requirements by trapping and digesting insects and other small animals. The trapped insects are killed and their proteins are digested by proteolytic enzymes secreted by the epidermis of the leaf. They can live without insects but their growth is stimulated when they digest the insects. The leaves of these plants are modified in several ways for trapping insects.
Example: Pitcher plants, Drosera, Utricularia and Dionea



(you can view this video for reference)







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