NCERT Class 11-Biology: Chapter –6 Anatomy of Flowering Plants Part 5

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Question 4:

What are the characteristic differences found in the vascular tissue of gymnosperms and angiosperms?

Answer:

The characteristic differences found in the vascular tissue of gymnosperms and angiosperms are as follows:

Gymnosperms, Angiosperms
Gymnosperms, Angiosperms

Gymnosperms

Angiosperms

(i) Vessels are absent in xylem

(i) Vessels are present in xylem

(ii) Companion cells are absent in phloem

(ii) Companion cells are present in phloem

Question 5:

Epidermal cells are often modified to perform specialized functions in plants. Name some of them and function they perform.

Answer:

Some of modified epidermal cells to perform specialized functions in plants with their functions are as follows:

i. Root Hair: It increases the surface area for absorption of water and minerals from the soils. Root hairs are unicellular elongations of the epidermal cells.

ii. Trichomes: They are also known as stem hairs. They help in water loss prevention during transpiration. Some trichomes have stinging purpose while others have glandular secretions. They may be unicellular or multicellular.

iii. Bulliform cells: Bulliform cells are present in grasses. They help in closing the stomata under stressful conditions and this prevents water loss. Bulli form cells are the modified adaxial epidermal cells along the veins in grasses. Bulliform cells are large, empty, colourless cells.

Question 6:

The lawn grass (Cyandon dactylon) needs to be mowed frequently to prevent its overgrowth. Which tissue is responsible for its rapid growth?

Answer:

Meristematic tissue is responsible for the rapid growth of lawn grass.

The meristems which occur at the tips of roots and shoots and produce primary tissues are called apical meristems.

When lawn is mowed the apical meristems get trimmed and the growth of grass stops. But the growth of lateral branches continues making the lawn look bushy.

Question 7:

Plants require water for their survival. But when watered excessively, plants die. Discuss.

Answer:

Plants die when watered in excess, because excess water removes the air trapped between the soil particles.

Plants use water for several metabolic processes as photosynthesis, transpiration and respiration.

Plant when watered excess its roots do not get enough oxygen for respiration. Once root cells die, water and mineral absorption is stopped and this leads to gradual death of a plant.

Hence irrigation should be supported with proper drainage of water to avoid water logging in the soil. Water logging draws salt to the surface of the soil. This salt gets deposited on roots of the plants. This increased salt content is dangerous to the growth of the crops and is extremely damages the plants and plants die.

Question 8:

A transverse section of the trunk of a tree shows concentric rings which are known as growth rings. How are these rings formed? What is the significance of these rings?

Answer:

The growth rings in the trunk of the tree are formed by cambial ring due to secondary growth.

Each ring contains early wood and late wood. Secondary growth occurs in dicot trees due to the activity of cambium which is a meristematic tissue.

The concentric growth rings are called annual rings.

The rate of activity of cambium is more in spring than in winter so wood formed has larger wider xylem cells and called spring wood or early wood, whereas wood formed in winter has narrower and smaller xylem elements and called autumn wood or late wood. And also the wood formed during spring is light-coloured with low density and the wood formed during winter is dark-coloured with high density. This result in the formation of alternate concentric rings called growth rings.

Question 9:

Trunks of some of the aged tree species appear to be composed of several fused trunks. Is it a physiological or anatomical abnormality? Explain in detail.

Answer:

Trunks of some of the aged tree species appear to be composed of several fused trunks. This is anatomical abnormality.

It is an abnormal type of secondary growth, where a regular vascular cambium or cork cambium is not formed in its normal position. In this case cortical and medullary vascular bundles are formed. This gives rise to the additional or accessory vascular bundles giving an appearance of additional trunk which appear to be fused trunk.

Question 10:

What is the difference between lenticels and stomata?

Answer:

Lenticels and Stomata
Lenticels and stomata

Lenticels

Stomata

1. They are lens shaped openings present on the trunk or stem of the tree

1. They are bean shaped opening present on the lower surface of leaves

2. They are formed due to loosening of the epidermal and cortical tissue.

2. Stomata are specialized epidermal structures

3. Guard cells are absent

3. Guard cells are present.

4. These opening are not regulated.

4. These opening are regulated

5. Facilitates removal of waste.

5. Facilitates exchange of gases.

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