Important Questions Class 11 Biology Chapter 6

Anatomy of Flowering Plants Important Questions Class 11 Biology Chapter 6

Have you ever looked around and thought about how beautiful flowers are? How are they classified? What is their structure and form? How do we even identify each flower differently?

Chapter 6 of Class 11 Biology in the NCERT book is about the Anatomy of Flowering Plants and it summarises all this essential information. It teaches about the tissues, the tissue system, the anatomy of dicotyledonous and monocotyledonous plants, and secondary growth. So, to understand the chapter, Anatomy of Flowering Plants, this article contains a few of the questions and their solutions from our Important Questions Class 11 Biology Chapter 6 for students to study and benefit from.

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Class 11 Biology Chapter 6 Question Answers

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Given below are some of the questions and their answers from our question bank of Chapter 6 Class 11 Biology Important Questions.It’s recommended for students who want to maximise their potential and get excellent grades in Biology.

Q1. Why Is the cambium considered a lateral meristem? 

Answer 1. The cambium is classified as a latent meristem because it appears along the latent side of the stem and roots. It also appears tater than primary meristem. Cells of this meristem divide periclinal and increase the thickness of the plant body.

Q2. How do open vascular bundles differ from closed vascular bundles?

Answer 2: The term open vascular bundle denotes that these types of plants are open for secondary growth. However, closed vascular bundles are those which are closed for secondary growth i.e secondary growth will not take place.

Q3. How can you differentiate a monocot stem and a dicot stem? Give reasons. 

Answer 3: 

Q4. How would you distinguish between them if you are provided with a microscopic preparation of a transverse section of meristematic tissue and permanent Tissue?

Answer 4: Meristematic tissues are composed of cells that can divide, and these cells exist in different shapes without intercellular space between them. These cells are thin-walled and rich in protoplasm. They do not contain vacuoles. While permanent tissues are derived from meristematic Tissue, their cells have a definite shape, size, and function. These cells can be thin-walled (living) or thick-walled (dead).

Q5. Are there any elements of phloem which are comparable to those of Xylem? Explain. 

Answer 5.

 (a) The phloem sieve elements are comparable to the Xylem vessel because of both tack nuclei. 

(b) Phloem and xylem fibre are similar because both provide tensile strength to the Tissue. 

(c) Phloem parenchyma and Xylem parenchyma are the living components of phloem and Xylem, respectively. 

Q5. PaIm is a monocotyledonous plant, yet it increases in girth. How is it possible? 

Answer 5. A pain louse is not a plant, hence does not have primary cambium in the vascular bundles of the stem. However, the tree grows in diameter. A secondary cambium may be found in the hypodermal region of the stem. The latter forms the conjunctive Tissue and patches of met cells. The activity of meristematic cells results in the formation of secondary vascular bundles. 

Q6. What is wood? What are Its different types?

 Answer6. Botanically, the secondary Xylem is called Wood. It is generated by the plant’s metabolism, which includes secondary growth by cambium that constitutes the bulk of the plant body in both the dicot stem & dicot root. Wood is classified into main categories.

(i)Hardwood: – Hardwood is the Wood produced by angiosperms. It consists mainly of xylem vessels, also called porous Wood. 

(ii)Soft Wood: – Softwood is the Wood produced by gymnosperms. It consists mainly of xylem tracheids & hence it is called a non-porous Wood. 

(iii) Heartwood: Heartwood is the central core of Wood formed during secondary growth. It consists of dead cells. The cells are dark in colour due to extractives like gums, resins, tannins, etc. 

(iv)Sap Wood: – It is the peripheral part of Wood formed during the secondary growth process. It consists of living cells, which are lighter in colour as the extractives are not present. 

(v)Early Wood: – Earlywood is the Wood formed during a favourable season. It mainly consists of vessels and tracheids. 

(vi)Late Wood: – Latewood is the Wood formed during unfavourable seasons. It mainly consists of vessels & tracheids.

Q7.Describe the internal structure of the monocot root. 

Answer 7. A Transverse section of the monocot root shows the following tissues:

(a)Epidermis: – Epidermis is the outermost root layer with no intercellular spaces, stomata, or cuticles. It also bears unicellular root hairs. 

(b)Cortex: – Cortex is present beneath the epidermis layer. It contains many layers of parenchymatous cells that have large intercellular spaces between them. 

(c)Endodermis: – The innermost layer of the cortex is called the Endodermis. The cells of the Endodermis are barrel-shaped with Casparian strips on their antifungal walls. The passage cells are seen just opposite the protoxylem ends. 

(d)Pericycle: – It consists of a single layer of thin-walled parenchymatous cells.

(e)Vascular Bundle: – The vascular bundles are radial, alternating Xylem & phloem. The xylem & phloem bundles are always more than six. The Xylem is exarch in condition. A large pith of parenchymatous cells occupies the central portion of the vascular bundles. The conjunctive Tissue is found between the xylem & phloem strands.

Q8. What are the three tissues systems classified in flowering plants? Name the tissues under every system.

Answer 8.

In flowering plants, there are three basic tissue systems:

(a) Dermal tissue system – It is composed of the epidermis layer, which helps in protection. But during secondary growth, it is replaced by periderm.

(b) Vascular tissue system – It consists of Xylem and phloem, found in the stele. In the root system, the vascular bundles are renal and found in exarch conditions, whereas, in the stems, these vascular bundles are collateral.

(c) Ground or Fundamental Tissue – It includes all the tissues except dermal and vascular, which act as parenchyma and sclerenchyma cells. It is found mainly between the epidermis layer and vascular cylinder and is formed of thin-walled cells that include intercellular spaces between them. Collenchyma cells are usually thickened at the corners , whereas Sclerenchyma c is dead Tissue, without protoplast and provide mechanical support.

Q9. What do you mean by heartwood? Mention any two main characteristics of heartwood.

Answer 9.

Heartwood is the hard central region of a tree trunk made up of xylem vessels that are not a part of the conduction as well as in the transportation of water.

The two main characteristics of heartwood are- 

1. It is present in a non-functional and dead position.
2. It is dark coloured in nature and filled with resins, tennis etc.

Q10 Point out the four major limitations of Wood.

Answer 10

The major limitations of Wood are 

as follows:

1. i) It cannot change its physical and mechanical properties when its temperature increases.
2. ii) It cannot be changed into new shapes and forms.

iii) It is the least resistant to infection caused by microorganisms and decay.

1. iv) It is combustible.

Q11. Why should we study plant anatomy?

Answer 11.

Plant anatomy helps to learn plant structure and solve various taxonomic problems related to medicine. Determining various pollutants in spices, coffee, tea, and tobacco saffron n is possible only when one knows this substance’s anatomy and morphants.

Pharmacology depends upon the anatomical studies of plant species to know about the drug plants and their actions on the human body. It also helps in forming spurious materials, which helps forensic experts in solving criminal cases.

Q12. How is a cambial ring formed in a dicotyledonous root?

Answer 12.

Perennial dicotyledonous roots show secondary growth because of the formation of secondary meristems. At the same time, some parenchymatous cells in the phloem become meristematic. These cells then divide and generate cambium strips. 

This cambian ring lies on the inner side of the phloem cells. It is also cut off from the cambium on the inner and outer sides. The inner side cells generate secondary Xylem, while the outer side cells of the cambium generate secondary phloem. The primary phloem comes on the outside as the cambium forms a complete ring.

Q13. Explain  the phloem of an angiosperm with its components briefly.

Answer 13.

Phloem is food and mineral conducting Tissue which consists of –

1. Sieve elements: Sieve elements occur as a single cell in pteridophytes, gymnosperms and longitudinal files of cells in angiosperms. The morphological specialisation includes developing a sieve area on the walls bearing sieve plates. Also, the sieve plate bears many perforations.

The protoplasmic strands are continuous through these perforations within the adjacent sieve tubes. A thin layer of parietal cytoplasm and a large central vacuole is formed in a mature sieve element. One of the major important features of sieve elements is that they lack a nucleus at maturity.

2. Companion cells: Companion cells are thin-walled, containing living narrow parenchyma cells closely associated with the sieve tube elements. They appear rounded or polygonal, containing dense granular cytoplasm, a prominent nucleus, and numerous small vacuoles. These companion cells lack starch.

The nuclei of the companion cells serve as the common nucleus of sieve tubes because they lack them. The companion cells mainly occur in angiosperms, accompanying the sieve tube elements.

3. Phloem fibres: Phloem fibres form a prominent part of the primary and secondary phloem. They contain elongated cells with lignified walls having simple pits. These cells provide support and help in the transportation of food material. They are also used for making cords and ropes etc.
4. Phloem parenchyma: Phloem parenchyma are the living parenchyma cells associated with sieve tube cells. These cells are elongated along with sieve tube cells. These cells are elongated and pointed in shape and store starch, fat, and other organic substances. The tannins and resins are also found in these cells, and They too are elongated like the sieve elements.

The sieve element is considered a living component which lacks a nucleus at maturity.

Q14. Define the following terms.

(i) Radial vascular bundles

(ii) Collateral vascular bundles

(iii) Exarch Xylem

(iv) Endarch xylem

(v) Stele

Answer 14.

(i) Radial vascular bundles: These are the bundles where the Xylem and phloem are arranged in different radii alternating. They also form separate bundles, which are called radial vascular bundles.

(ii) Collateral vascular bundles: These are the bundles where the Xylem and phloem are not arranged at the same radius. The Xylem is located internally, while the phloem is located externally. These can be open when there is a patch of cambium in between the Xylem and phloem, like in Helianthus, or they can be closed when there is no cambium at all. Like in the monocot stem.

(iii) Exarch xylem: It is the condition where the protoxylem is located towards the periphery of the axis while the metaxylem is located inwards, like in the root.

(iv)Endarch Xylem: It is the condition where the metaxylem is located towards the periphery of the axis while the protoxylem is located inwards, like in the stem.

(v) Stele: All the tissues that lie internal to endodermis are collectively called stele. The outermost layer of steel is known as the pericycle.

Q15. 

Distinguish between:

(i) Phellem and Phelloderm

(ii) Open Bundle and closed Bundle

(iii) Fascicular cambium and inter fascicular cambium

(iv) Conjoint vascular bundles and Radial vascular bundles

(v) Periderm and Bark

Answer 15.

(i) Phellem and Phelloderm

Philem: Philem is a dead tissue formed by the cork cambium’s activity in the cortex’s outer regions during secondary growth. It is protective in function.

Phelloderm: On the other hand, phelloderm is a living tissue formed by the cork cambium’s activity in the cortex’s inner side. It regains and regrows during secondary growth. It performs the function of storage.

(ii) Open Bundle and closed Bundle

Open Bundles are classified as avascular bundles containing cambium between Xylem and phloem. Like in a dicot stem.

Closed Bundles are classified as avascular handles lacking cambium between Xylem and phloem. Like in a monocot stem.

(iii) Fascicular cambium and inter fascicular cambium

The fascicular cambium is a cambium strip found between the Xylem and phloem of each vascular Bundle of a dicot stem.

Interfascicular cambium is a cambium strip formed from the cells of medullary rays adjoining the fascicular cambium. Dining secondary growth occurs.

(iv) Conjoint vascular bundles and Radial vascular bundles

Conjoint vascular bundles contain Xylem and phloem, which lie in the same bundles. They also lie on different radii alternating with each other. The most common example is dicot and monocot root.

(v) Periderm and Bark

Answer:

Periderm: It includes three tissues consisting of phellogen, phellem and phelloderm. These cells are formed in the peripheral region of the axis.

On the other hand, bark includes all the Tissue external to the secondary Xylem formed during secondary growth. These are cambium and secondary phloem.

Q16. What is a stomatal apparatus? Explain briefly. .

Answer 16.

Stomata are structures that are present in the epidermis of leaves. They regulate the process of transpiration and gaseous exchange. Each stoma present is composed of two bean-shaped cells called guard cells. They enclose a stomatal pore.

These guard cells are dumbbell-shaped, where the outer wall is thin and the inner wall is thick. These structures possess chloroplasts which regulate the closing and opening of the stomata. The epidermal cells present near the guard cells become specialised in their structure, shape, and size. They are commonly referred to as subsidiary cells. The guard cells, the stomatal aperture and girdling subsidiary cells are collectively known as the stomatal apparatus.

Q17. What is the periderm layer? How does the formation of Pyridium take place in dicot stems?

Answer 17.

Phellogen, phellem, and phelloderm are collectively referred to as periderm. While plants undergo secondary growth and development, the outer epidermal and cortical layers are ripped due to cambium. To replace the layers, the cortex cells turn meristematic, which produces the cork cambium or the phellogen, which comprises thin-walled, narrow and rectangular cells

The phellogen sheds cells on either side. The cells shed from the exterior give rise to the cork or phellem. The suberin accumulates in its cell wall, making it impervious to water, while the inner cells emerge to become the secondary cortex or phelloderm, which is parenchymatous.

Q.18 Describe the internal structure of a dorsiventral leaf.

Answer 18.

Dicots exhibit dorsiventral leaves. When examined under a microscope, the vertical section of a dorsiventral leaf consists of three main parts, they are:

1. Epidermis –The epidermis is the outermost root layer with no intercellular spaces, stomata, or cuticles. It also bears unicellular root hairs. 
2. Mesophyll – it is a tissue found in between the abaxial and adaxial epidermises. This Tissue is

differentiated into the palisade parenchyma and the spongy parenchyma. The palisade parenchyma comprises tall, compactly arranged cells, while the spongy parenchyma comprises round or oval, loosely-arranged cells possessing intercellular spaces. Mesophyll comprises chloroplasts that carry out photosynthesis.

3. Vascular system – The vascular bundles found in leaves are closed and conjoint, engirdled by thick layers of bundle-sheath cells.

Q.19 Phellogen and phellem, respectively, denote

(a) Cork and cork cambium 

(b) Cork cambium and cork

(c) Secondary cortex and cork 

(d) Cork and secondary cortex

Answer 19. Option b is the right answer.

Explanation – Phellogen and phellem, respectively, denote cork cambium and cork.

Q.20 What is the epidermal cell modification in plants which prevents water loss?

Answer 20.

 In grasses, certain adaxial epidermal cells along the veins modify themselves into large, empty, colourless cells. These are called bulliform cells or motor cells. Bulliform cells help in the folding and unfolding of grass leaves.

The leaf surface is exposed when the bulliform cells in the leaves have absorbed water and are turgid. When flaccid due to water stress, the leaves curl inwards (inrolling) to minimise water loss (transpiration).

Q21. Epidermal cells are often modified to perform special functions in plants. Name some of them and the functions they perform.

Answer 21.- Some of the special functions epidermal cells perform are:

• Root hairs: The root hairs are unicellular elongations of the epidermal cells and help absorb water and minerals from the soil.
• Stem hairs or trichomes: The epidermal hairs are called trichomes on the stem. The trichomes present in the shoot system are usually multicellular.

They may be branched or unbranched. They may even be secretaries. One of the trichomes’ major functions is to help prevent water loss due to transpiration.

• Bulliform cells: In grasses, certain adaxial epidermal cells along the veins modify themselves into large, empty, colourless cells. These are called bulliform cells. The leaf surface is exposed when the bulliform cells in the leaves have absorbed water and are turgid. When flaccid due to water stress, the leaves curl inwards to minimise water loss.

Q22. What is the difference between lenticels and stomata?

Answer 22. 

In certain regions, the phellogen cuts off closely arranged parenchymatous cells on the outer side instead of cork cells. These parenchymatous cells soon rupture the epidermis, forming lens-shaped openings called lenticels.

• Lenticles permit the exchange of gases between the outer atmosphere and the internal Tissue of the stem. These occur in most woody trees. Lenticels remain open permanently.
• Stomata are structures present in the epidermis layer of leaves. Stomata regulate the process of transpiration and gaseous exchange. Each stoma comprises two bean-shaped cells known as guard cells which enclose the stomatal pore. In grasses, the guard cells are dumbbell-shaped, where the outer walls of guard cells are away from the stomatal pore, and the inner walls are situated towards the stomatal pore. The guard cells possess chloroplasts which regulate the opening and closing of stomata.

Q 23. What is  the smallest unit of life?

Answer 23. The cell is the smallest unit of life.

The cells can divide, multiply, grow and respond to environmental stimuli. Almost all cells, except primitive cells like bacteria and viruses, are composed of the cytoplasm and the nucleus. Also, they have the basic plasma cytosol and a colloidal structure.

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