Lesson: Nutrition in Plants

# Question: 1

Which two living organisms form lichen?

## Solution:

Algae and fungi form lichen.

# Question: 2

How do an alga and fungus exhibit a symbiotic relationship in lichen?

## Solution:

In lichen the alga prepares food, while the fungus provides shelter, minerals, and water.

# Question: 3

Write down the names of four plants that derive food from ways other than the photosynthesis.

## Solution:

1.  Mushroom

2.  Lichens

3.  Pitcher plant

# Question: 4

## Solution:

(a) Parasitic, eg., cuscuta

(b) Symbiotic, eg., lichens, Rhizobium

(c) Autotrophic, eg., all green plants

(d) Saprophytic, eg., fungi

(e) Insectivorous, eg., pitcher plant

# Question: 5

## Solution:

(a) Carbon dioxide

(b) Sunlight

(c) Chlorophyll

(d) Water

Cuscuta

# Question: 7

## Solution:

To prevent fungal infection and food spoilage.

# Question: 1

Why are nitrogenous fertilizers needed for the soil after harvest (except legumes)?

## Solution:

Crops need large quantities of nitrogen in order to make proteins, which make the soil nitrogen deficient, after harvest. Hence nitrogenous replenishment is needed in the form of fertilizers.

# Question: 2

What is the mode of nutrition in fungi?

## Solution:

Fungi secrete digestive juices on dead and rotting matter, converting them into a solution, from which they take in nutrients. This type of nutrition, as seen in the fungi, is called saprotrophic nutrition, where an organism absorbs nutrients in the form of a solution, from dead and rotting matter, and plants showing this mode of nutrition are called saprotrophs.

# Question: 3

Why food and other objects not in regular use, should be kept carefully during the rainy season?

## Solution:

Fungi grow well in warm and humid climate, and they proliferate best during the monsoon season. It is for this reason that food and other objects not in regular use, must be kept carefully during monsoons, to avoid the growth of fungus on them that spoils these items.

# Question: 4

How does fungus start growing on bread left unused for some days?

## Solution:

Fungal spores are often present in the air around us. When these spores land on warm and wet matter they germinate and develop to form fungi. So, when fungal spores land on unused bread, they germinate and bread mould (a form of fungus) starts growing.

# Question: 5

Why does Rhizobium grow on roots?

## Solution:

Rhizobium grows on roots because it cannot prepare its own food. However, it can fix atmospheric nitrogen, so it lives in a symbiotic association with leguminous roots, where it provides nitrogen to the plants, and in turn gets food form the plants.

# Question: 6

Differentiate between saprophyte and autotroph.

## Solution:

Saprophytes prepare their food by secreting digestive juices on dead and rotting matter, converting them into a solution from which they absorb nutrients.

Autotrophs prepare their own food from the raw materials available in the atmosphere, such as, sunlight, air and water. Example: all green plants.

# Question: 7

Why is food important for all living organisms?

## Solution:

Food is essential for all living organisms to develop their bodies, to grow and repair damaged cells and tissues, and to provide energy necessary for carrying out the different life processes.

# Question: 1

## Solution:

In plants, food is prepared in the leaves. Water and minerals from the soil are absorbed by plant roots, and sent to the leaves. Carbon dioxide present in air moves into leaves through tiny pores called stomata that are present on leaf surfaces. The green pigment chlorophyll found in leaves helps to capture sunlight energy, which is used to prepare food from water and carbon dioxide. Since the food is prepared in the presence of sunlight, the process is termed as photosynthesis (photo: light and synthesis: to combine).

# Question: 2

Define autotrophic and heterotrophic modes of nutrition.

## Solution:

Autotrophic nutrition: the term means self-nutrition, or living organisms that can prepare their own food, as for example, plants.

Heterotrophic nutrition: when organisms cannot prepare their own food and take in food prepared by the plants, therefore deriving nutrition directly or indirectly from plants, as for example, all animals are heterotrophic.

# Question: 3

What is a saprophyte? Give examples.

## Solution:

Saprophytes secrete digestive juices on dead and rotting matter, converting them into a solution, from which they take in nutrients. This type of nutrition is called saprotrophic nutrition, where an organism absorbs nutrients in the form of a solution, from dead and rotting matter, and plants showing this mode of nutrition are called saprotrophs. Example: mushroom, mould, mucor, etc.

# Question: 4

Draw a well labelled diagram of a leaf cell and explain briefly.

## Solution:

During photosynthesis, Carbon dioxide from air is taken in through the tiny pores present on the surface of the leaves which are surrounded by ‘guard cells’ and these pores are called stomata. The leaves have a green pigment called chlorophyll. It helps leaves to capture the energy of the sunlight which help in the process of photosynthesis.

# Question: 5

If you were a farmer which crop would you plant at least once annually, if you wish to avoid using nitrogenous fertilizers?

# Question: 6

How do pitcher plants trap insects?

## Solution:

The pitcher plant has a pitcher-like structure which is a modified leaf. The leaf apex forms a lid on the pitcher, and can open and shut. There are hairs inside the pitcher directed downwards. When an insect enters the pitcher, the lid shuts down and the insect gets entangled in the hair inside. The pitcher then secretes digestive juices which help to digest the insect.