Nutrition in Plants

How do plants get their food?

Plants can manufacture their own food, but animals including human beings cannot and rely on plants for their food.

All living organisms need food for the following :

• Cell regeneration
• Energy for cellular functions
• Immunity against diseases
• Plants make their foods using either the Autotrophic nutrition and Heterotrophic nutrition.

What is Autotrophic nutrition?

When green plants make their food using simple substances like sun light, water, carbon dioxide and minerals, the process is known as Autotrophic nutrition. This type of nutrition is also known as Holophytic nutrition. These types of plants are known as autotrophs. The words, ‘auto’ means self and ‘trophos’ means nourishment. Autotrophs are the producers in a food chain.

What is Heterotrophic nutrition?

A heterotroph is an organism that cannot manufacture its own food by carbon fixation and therefore derives its intake of nutrition from other sources of organic carbon, mainly plant or animal matter. In a food chain, heterotrophs are secondary and tertiary consumers. This is also known as Holozoic nutrition, as the food is ingested and goes through a digestive process.

What are the types of Heterotrophs?

The types of heterotroph are :

1. The animals that are directly dependent on plants are called herbivores. For example – Deer, Cow, Goat and Rabbit.
2. The animals that eat the flesh of other animals are called carnivores. For example – Lion, Tiger, Wolf and Snake.
3. The animals that feed on both plants and animals are called omnivores. For example – Man, Bear and Crow.
4. The animals that feed on the flesh of dead animals are called scavengers. For example – Kites and Vultures.

Photosynthesis in plants

Plants manufacture their food in their leaves. The leaves, are therefore, also known as the kitchen or food factories of the plants. Photosynthesis is the combination of two words – Photo and synthesis. ‘Photo’ means light and ‘synthesis’ means to make.

The reaction that takes place in the process of photosynthesis can be written as :

6CO2 + 6H2O ——> C6H12O6 + 6O2

Plants require the following things to carry out the process of photosynthesis –

• Sunlight
• Water
• Carbon – dioxide
• A green pigment known as the Chlorophyll

Leaves have numerous small pores like structures on their lower surface. These pores are surrounded by ‘guard cells’. These pores are called stomata. The stomata are guarded by two bean-shaped cells known as the guard cells. Leaves absorb carbon dioxide from air through stomata. Water is transported to the leaves through the Xylem tissue.

What is chlorophyll?

Chlorophyll is a green pigment found in the leaves. It gives the leaves their characteristic green colour. The job of chlorophyll is to absorb sunlight, carbon dioxide and water and convert them into carbohydrate and oxygen.

Importance of photosynthesis

The process of photosynthesis is very useful for our environment. It maintains a balance between the concentration of oxygen and carbon dioxide in the atmosphere. Plants release oxygen that is essential for our survival and that is why it is said that we must plant more trees.

What are the modes of nutrition in non-green plants?

There are some plants that lack chlorophyll. Such plants are also known as non-green plants and they cannot synthesise their own food. They depend on other organisms for food. Let us learn about some of the important non – green plants.

1. Parasitic plants

A parasite is an organism which lives on or inside the body of another organism and takes shelter and food from that organism. An organism which provides shelter and nutrition to another organism is called a host. The host in this case is always at loss.

Plants that get their food from other plants by living on them are called parasitic plants. For example – Cuscuta or Amarbel and Mistletoe. Cuscuta is a vine-like plant with a yellow coloured stem. It coils around big trees, like the Banyan tree and gets nutrition from it. In this case, Banyan tree is the host and Cuscuta is the parasite.

2. Insectivorous plants

The plants that eat insects are called insectivorous plants. They trap and digest the insects. For example – Pitcher plant is an insectivorous plant in which the leaves are modified into pitcher – shaped structures. The insects get attracted to the bright colour and sweet-smelling nectar of the pitcher plant. When an unsuspecting insect sits on the pitcher of the plant to take a sip of the nectar, the lid of the pitcher closes and the insect gets trapped inside. The insect is then digested by the enzymes released by the cells of the plants. Venus flytrap, Utricularia and Drosera are some other examples of insectivorous plants which trap and kill small flies and spiders in different ways.

3. Saprotrophs

The non-green plants that feed on the dead and decaying matter like animal wastes are called Saprotrophs or Saprophytes. For example – Fungi like Agaricus, Yeast and Bacteria.

4. Symbiotic plants

Symbiosis is the combination of two Greek words ‘Sym’ means ‘with’ and ‘biosis’ means ‘living’. In other words, symbiosis means ‘living together’. Symbiosis is the type of nutrition in which two different kinds of living organisms depend on each other for survival. They share shelter and nutrients. For example – Lichen. Lichen is a composite organism made up of fungus and alga. Fungus is a saproptroph and alga is an autotroph. The fungus provides water and minerals to the alga and in return the alga supplies food prepared by photosynthesis to the fungus.

3 Interesting facts about plants

1. Insectivorous plants generally grow in swamps or marshy areas because the soil in such areas is deficient in nitrogen. To fulfill their nitrogen need, the plants trap and kill the insects.
2. There are roughly 600 species of carnivorous plants which have different strategies to capture their prey.
3. Charles Darwin was very fond of the carnivorous plant – Sundews, or Drosera.