Class VII Science Chapter 1: Nutrition in Plants

       Carbohydrates, proteins, fats, vitamins and minerals are the basic components of food and termed as nutrients.

    Nutrients help the organisms to grow, to build their bodies, to repair damaged parts and also provide energy to sustain the  life  processes.

Green plants prepare their own food in their own body;but animals including humans cannot make their own food in their body.Hence, they have to procure these nutrients from outside, for this they depend upon the plants directly or indirectly.

Mode of Nutrition in Plants:

The mode of taking food by an organism  and it's utilisation by the body is called  Nutrition.

Types of Nutrition: Nutrition are of two types, Autotrophic and Heterotrophic.

Auto=self

Heteros=other

Trophos=nourishment

*If organisms make food themselves in their own body from simple substances like carbon dioxide and water, then this mode is called Autotrophic Nutrition.

Example: Green plant's mode of Nutrition.

*The organisms which are not able to make their food in their own body and for this reason they take ready made food made by plants directly .This mode is called Heterotrophic Nutrition.Example Nutrition of human and other animals.

Green pigments called chlorophyll are the food factories  of a plant and located in green parts , especially leaves and young stems.

Carbon dioxide of air, water and 🌞 sunlight are the simple raw materials used by a plant during food making process .

A Plant absorbs water by it's roots and transports to the leaves through tubes called xylem ;it absorbs atmospheric carbon dioxide by stomata and trap solar  energy in it's green parts especially leaves.

Stomata are the tiny pores present on the surfaces of leaves .A stoma is guarded by two guard cells which control the opening and closing of it.

"Leaves are green"Why?

There are many green pigments called chlorophyll in green parts of a plant , so leaves are green.These pigments are located in packets called chloroplast.

Food Making Process in Plants

 Generally  plants make their food in green parts,  during this carbon dioxide gas is absorbed from air and  oxygen gas liberate from the leaves through stomata.

This Autotrophic mode of food making is called Photosynthesis (Photo=light; synthesis=to combine).

The overall equation of photosynthesis is given below:

Carbon dioxide+water-----------------------> carbohydrates+oxygen+water

*A leaf has a maximum number of stomata.

*It has flat surface to receive sunlight.

*It has a maximum number of green pigments.

*It has a maximum network of conducting pipes.

For the above factors a leaf is considered as the ideal site of photosynthesis.

Sun and energy

Fig: Diagram of photosynthesis

•Sun provides us light energy.

•This energy is captured by green leaves and stored in the plant in the form of carbohydrates.

•This carbohydrate is then converted to starch .

•When an animal eats any part of a plant then solar energy  is transferred from plants to animals or  from animal to animal in the form of food .

• After the death of a plant or animal stored energy is stored in fossil fuel like crude oil , coal,etc.

Thus,in absence of sun photosynthesis will stop, as a result oxygen supply as well as energy supply will stop.Hence, we can say that sun is the ultimate source of energy.

Fig.Transfer of solar energy from grass to cows

 Various coloured leaves and     photosynthesis

          There are many more plants having variuos coloured leaves.These leaves too perform photosynthesis , because the green pigments are masked by red, brown and other colours.Since,these leaves have green pigments they too perform photosynthesis.

Algae too perform photosynthesis

Fig.Green algae

Algae are the aquatic plants and most of them are green due to the presence of chlorophyll, so they do Photosynthesis.

Synthesis of plant food other than carbohydrates

Carbon(C), hydrogen(H) and oxygen (O) make carbohydrates.Plants synthsise proteins and fats by these elements.But plants need nitrogen(N) to make protein along with C,H and O.

Atmosphere contains 78% N ,but no one can consume this N directly though N is a basic component of DNA, RNA ,amino acids and proteins.There are some exceptions, a few blue green algae like Nostoc, Anaebaena ,etc. and a few bacteria like Rhizobium can convert atmospheric N into plant absorbable form in soil.Moreover farmers add N in the soil while they add NPK fertilizer.

Fig.Root nodules containing numerous Rhizobium bacteria.

(Photo source Wikipedia)

Other Modes of Nutrition in Plants

There are a few non green plants which cannot make their own food. To carry all life processes they perform Heterotrophic mode of Nutrition. They may be parasitic, saprophytic and others.

Parasitic Plant

Amarber/Swarnalata/Cuscuta is a non green plant.It lives on other photosynthetic plants and absorbs prepared food from the host by  it's numerous haustoria .

Saprophytic Plants

Fig.Penicillium

Fig. Polyporous on decaying wood

Yeast,  Penicillium, Polyporous etc are non-green and termed as Fungi.These  are also termed as Saprotrophs and procure food by the following way: 

•These plants grow on  living or dead organic matter and then release enzymes to make it absorbable form.Then they absorb and procure food from them.

Since, they obtain food from decaying substances, their mode of  Nutrition is called Saprophytic and they are termed as Saprotrophs. 

Insect 🦋 Eating Plants

There are a few plants like pitcher plant, Drosera,Utricularia etc .  need a large amount of N .They fulfill this N requirment by eating insects. These plants first capture insects and then digest them.At last they absorb N from the digested insesects. Such insect-eating plants are called insectivorous plants.

Fig.Venus flytrap(Drocera)

Fig.Pitcher plant (Nepenthes)

Fig.Bladder wort (Utricularia)

Photo source Wikipedia

There are a few examples where two partners live in mutual relationship.First example is Lichen.

Fig.Lichens on the bark of a plant

A Lichen is a combination of algae and fungus.Non green fungus provides water to the algal partner, in responce alga gives prepared food to the fungi.This mutual relationship is called symbiosis and the Lichen is called  as a symbiont.

What we have learnt

•Most plants are Autotrophs.

•Fungi are Saprotrophs.

•Cuscuta is a parasitic plant.

• Pitcher plant is insectivorous.

•Lichen is a symbiont.

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