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Class 11 Biology Chapter 6 Anatomy of Flowering Plants
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Anatomy of Flowering Plants
Chapter – 6
VERY SHORT ANSWER TYPE QUESTIONS
Q.1. Define tissue.
Ans :- A tissue is a group of cells having a common origin performing a common function.
Q.2. Into how many groups are the tissue classified? Name them.
Ans :- The tissue are classified into two groups – They are meristematic and permanent tissue.
Q.3. What are meristematic tissue?
Ans :- The young cells having the power of division are called meristematic tissue.
Q.4. What are the types of meristematic tissue?
Ans :- There are three types of meristematic tissue –
(i) Apical meristem
(ii) Intercalary meristem
(iii) Lateral meristem
Q.5. What are permanent tissue?
Ans :- When cells become structurally and functionally specialised and lose the ability to divide, such cells are called permanent tissue.
Q.6. How many types of permanent tissue are there?
Ans :- There are two types of permanent tissue – simple and complex tissue.
Q.7. What type of cells are observed in parenchyma?
Ans :- The cells of parenchyma are generally isodiametric. They may be spherical, oval, round in shape.
Q.8. What is the function of collenchyma cells?
Ans :- Collenchyma cells provide mechanical support to the growing part of the plants.
Q.9. Give a few example of sclerenchyma tissue.
Ans :- Fruit wall of nuts, pulp of fruit like guava, pear and sapota, seed coat of legume and leaves of tea.
Q.10. What is the function of xylem?
Ans :- Xylem functions as a conducting tissue for water and minerals from roots to the stem and leaves. It also provide mechanical strength to plant parts.
Q.11. Mention the names of element found in xylem?
Ans :- The kinds of elements found in xylem are – Tracheid, Vessels, Xylem fibres and xylem parenchyma.
Q.12. What are ‘tracheids’?
Ans :- Tracheids are elongated or tube like cells with thick and lignified walls and tapering ends.
Q.13. What is the basic difference between xylem fibres and xylem parenchyma?
Ans :- Xylem fibres have highly thickened walls and xylem parenchyma cells are living and thin walled.
Q.14. Classify different types of xylem?
Ans :- Xylem is classified into two types – protoxylem and metaxylem.
Q.15. What is exarch xylem?
Ans :- When protoxylem lies towards periphery and metaxylem lies towards the centre, such xylem is said to be exarch xylem.
Q.16. Write the main function of phloem?
Ans :- Phloem transports food materials, usually from leaves to three parts of the plant.
Q.17. Write the main elements found in phloem?
Ans :- The main element present in phloem are sieve tube, companion cells, phloem parenchyma and phloem fibres.
Q.18. What is the chief function in companion cells?
Ans :- Companion cells help in maintaining the pressure gradient in sieve tubes.
Q.19. Classify different types of phloem.
Ans :- Phloem is classified into two types – protophloem and metaphloem.
Q.20. Write the names of the cells which comprises the epidermal tissue system?
Ans :- The epidermal tissue system comprises of – epidermal cells, stomata and epidermal appendages, trichome and hairs.
Q.21. What is ‘cuticle’?
Ans :- The epidermis is covered with a waxy thick layer called the cuticle which prevents the loss of water.
Q.22. What is the function of stomata?
Ans :- The main function of stomata is to regulate the process of transpiration and gaseous exchange.
Q.23. What are mesophyll cells?
Ans :- In leaves, the ground tissue consists of thin walled chloroplast containing cells called the mesophyll cells.
Q.24. What are open vascular bundle?
Ans :- When cambium is present between xylem and phloem, then such vascular bundle possess the ability to form second xylem and phloem tissue. The vascular bundle here is called open vascular bundle.
Q.25. What is a conjoint vascular bundle?
Ans :- In conjoint type of vascular bundle, xylem and phloem are situated at the same radius of the vascular bundle.
Q.26. What is a conjunctive tissue?
Ans :- The parenchyma cells which lie between the xylem and phloem are called conjunctive tissue.
Q.27. What is periderm?
Ans :- Phellogen, phellem and phelloderm are collectively called periderm.
Q.28. What are lenticels?
Ans :- When the parenchymatous cells rupture the epidermis shape lens opening is formed. This is known as lenticels.
Q.29. Define bark.
Ans :- Bark are the tissues exterior to the vascular cambium.
Q.30. Do monocotyledons show secondary growth ?
Ans :- No, secondary growth do not occur in monocot.
SHORT ANSWER TYPE QUESTIONS
Q.1. Write a note on meristematic tissue.
Ans :- Meristematic tissue consists of young cells having the power of division. These are located in the growing region of plant such as a tip of root and a stem. The cells are thin, possess dense cytoplasm with permanent nucleus and are compactly arranged without any intercellular space.
According to position, meristematic tissue is of three types – apical, latera and intercalary meristem according to origin and development meristematic tissue are of three types – promeristem, primary meristem and secondary meristem.
Q.2. Describe parenchyma tissue in brief.
Ans :- Parenchyma forms the major component within organs. The cells of parenchyma are generally isodiametric. They may be spherical, oval, round, polygonal or elongated in shape. Their walls are thin and made up of cellulose. They may be either closely packed or small intercellular spaces.
Parenchyma performs various function like photosynthesis, storage and secretion.
Q.3. Write an account on collenchyma tissues.
Ans :- Collenchyma occurs in layers below the epidermis in dicots. It consists of which are much thickened at the corners due to the deposition of cellulose, hemicellulose and pectin collenchymatous cells may be oval, spherical or polygonal and often contain chloroplasts. Intercellular spaces are absent.
Collenchymatous tissue provide mechanical support to the growing parts of the plant such as young stem and petiole of the leaf.
Q.4. Describe sclerenchyma tissue in short.
Ans :- Sclerenchyma consists of long, narrow cells with thick and lignified cell walls having a few or numerous pits. They are usually dead and without protoplast. Sclerenchyma may be either fibres or sclereids in form. The fibres are thick walled, elongated and pointed cells, generally occurring in groups. Sclereids are spherical, oval or cylindrical, highly thickened dead cells with very narrow cavities.
These are commonly found in the fruit wall of nuts, pulp of fruits like guava, pear and sapota, seed coat of legume and leaves of tea.
Sclerenchyma provides mechanical support to the organs.
Q.5. Why are xylem and phloem are called complex tissue?
Ans :- Complex tissue are made up of more than one type of cells and these works together as a unit. Xylem is composed of four different kind of elements – tracheids, vessels, xylem fibres and xylem parenchyma. Tracheids and vessels are the main water transporting element. Xylem fibre provides mechanical strength and xylem parenchyma serves as a storage organ.
Phloem is composed of your different kinds of elements – sieve tube, companion cells, phloem parenchyma and phloem fibre. Sieve tube is meant for conduction of prepared food. Companion cells assists the sieve tube in the conduction of food. Phloem parenchyma stores food and help in conduction and phloem parenchyma give mechanical support.
Thus it is clear that all the elements of xylem and phloem together work as a unit hence, xylem and phloem are called complex tissues.
Q.6. Classify different types of xylem.
Ans :- Xylem is classified into two types –
(i) Protoxylem :- It is the first formed xylem with small diameter.
(ii) Metaxylem :- It is the later formed xylem with wider lumen.
On the basis of distribution of protoxylem and metaxylem, xylem is classified into following types :
(i) Exarch :- Protoxylem lies towards periphery and metaxylem lies towards the centre e.g. root.
(ii) Endarch :- Protoxylem lies towards centre and metaxylem lies towards periphery e.g. stem.
Q.7. Write a brief note on the elements of phloem.
Ans :- Phloem is composed of four elements – sieve tube, companion cell, phloem parenchyma and phloem fibres.
Sieve tube :- These are elongated tube like cells placed end to end. These are meant for conduction of prepared food.
Companion cell :- It is living cell with dense protoplasm associated with sieve tube end to end.
Phloem parenchyma :- Parenchymatous cells found associated with sieve tube are called phloem parenchyma. They store food and help in conduction.
Phloem fibre :- Sclerenchymatous cells found associated with phloem are called phloem or bast fibre. They have mechanical functions.
Q.8. Name the three basic tissues system in flowering plants. Give the tissue name under each system.
Ans :- The three basic tissue system in flowering plant are –
(i) Epidermal tissue system
(ii) Vascular tissue system
(iii) Ground tissue system
The tissues found in epidermal tissue system are epidermal cells, stomata and epidermal appendages – trichome and hairs.
The tissue found in ground tissue system are – parenchyma, collenchyma and sclerenchyma. The ground tissue consists of thin walled chloroplast containing cells are called mesophyll.
Q.9. Describe epidermal tissue system.
Ans :- Epidermal tissue system forms the outermost covering of the whole plant body. It is classified into following types – epidermis, epiblema and stomata.
Epidermis :- It is the outermost layer of the stem, leaf and various parts of the body. It is generally single layered. It is responsible for protection from external injury.
Epiblema :- The root epidermis is called epiblema. Some cells in the root hair zone have their outer wall extended in the form of narrow tube like bodies called root hairs.
It is mainly concerned with the absorption of water and mineral salts from soil.
Stomata :- Some minute pores called stomata are present here and there in the epidermis. Each stomata is guarded by two semilunar cells, known as guard cells. Stomata are used for gaseous exchange between atmosphere and plant.
Q.10. Differentiate between open and close vascular bundle.
Ans :- In dicotyledonous stem, cambium is present between phloem and xylem such vascular bundle because of the presence of the cambium possess the ability to form secondary xylem and phloem tissues and hence are called open vascular bundle.
But in monocotyledonous stem, vascular bundle have no cambium present in them. Hence, they do not form secondary tissues, they are referred to as close vascular bundle.
LONG ANSWER TYPE QUESTIONS
Q.1. Explain the process of secondary growth in the stems of woody angiosperms with the help of schedule diagrams. Write its significance.
Ans :- Dicotyledonous plants exhibit an increase in girth. This increase is called secondary growth. The tissue involved in secondary growth are – Vascular cambium and Cork cambium.
Cambium is a type of meristematic tissue found in association with vascular bundle. Initially, the fascicular cambium cuts off secondary xylem and secondary phloem which constitute the secondary tissues. These tissues are responsible for secondary growth. Secondary phloem remains outside and secondary xylem remains inside. The cambium lying inner side is more active and as a result of which more secondary xylem is produced to form a compact mass of xylem. As a result of continuous accumulation of more xylem inside, the outer tissue get pushed towards the periphery and thus the stem expands laterally to increase the girth.
In large woody plants the xylem vessels at the centre of stem become darker in colour due to decomposition of resin, gum, oil etc. This part of wood cannot conduct material but is strong to provide mechanical strength. This portion is known as heart wood. It has high timber value and is used for furniture. The less denser and light coloured region lying outside the heart wood region is called sap wood.
Cork formation :- The continuous division of cambium exerts great pressure on peripheral tissue. As a result the epidermis get ruptured here and there.
The gaps of the peripheral tissue caused by rupturing are filled up with strips of secondary meristem called phellogen or cork cambium and by tangential division of cells of phellogen, new cells are added on outer and inner faces. The outer cells lying just below the epidermis from the cork or phellem and the inner cells from the phelloderm. The phellogen, phellem and phelloderm together are called periderm.
Q.2. Describe the internal structure of dicotyledonous root with the help of labelled diagram.
Ans :- The internal tissue organisation of a dicotyledonous root is as follows : The outermost layer is epidermis. The epidermal cells protrude in the form of unicellular root hairs. The cortex consists of several layers of thin walled parenchyma cells with intercellular spaces. The innermost layer of the cortex is called endodermis. It comprises a single layer of barrel-shaped cells without any intercellular spaces. The endodermal cells have a deposition of water-impermeable, waxy material – suberin in the form of casparian strips. Next to endodermis lies a few layers of thick walled parenchymatous cells called the pericycle. The parenchymatous cells which lies between the xylem and phloem are called conjunctive tissue. There are usually two of four xylem and phloem patches. Later a cambium ring develops between xylem and phloem.
Q.3. Compare the anatomical structures of dicotyledonous and monocotyledonous stems.
Ans :- The transverse section of a dicotyledonous stem shows that the epidermis is the outermost protective layer of the stem. Covered with a thin layer of cuticle, it bear trichome and a few stomata. The cells arranged in multiple layers between epidermis and pericycle, constitutes the cortex. The cortex consists of three zones – outer hypodermis consisting of few layers of collenchymatous cells. Cortical layer below hypodermis consists of rounded thin walled parenchymatous cells with intercellular spaces. The innermost layer of the cortex is the endodermis. Pericycle is present on the inner side of the endodermis and above the phloem in the form of sclerenchyma patches. A large number of vascular bundles are arranged in a ring. This ring arrangement is the characteristics of dicot stem.
The vascular bundle is conjoint open and with endarch protoxylem. A large number of rounded parenchymatous cells with large intercellular space which occupy the centre portion of the stem constitute the pith.
But in monocot stem the hypodermis is sclerenchymatous, large number of scattered vascular bundles are present, each surrounded by a sclerenchymatous bundle sheath and also there is a large parenchymatous ground tissue, vascular bundle are conjoint and closed. Vascular bundle is the periphery are generally smaller than that at the centre. Phloem parenchyma is absent in monocot stem.
Q.4. Describe the internal structure of a dorsiventral leaf with a labelled diagram.
Ans :- The vertical section of a dorsiventral leaf shows three main parts – epidermis, mesophyll and vascular system. Epidermis covers both the upper and lower surface of leaf and also has cuticle. The lower epidermis bears more stomata than the upper epidermis. The tissue between the upper and lower epidermis is called the mesophyll. Mesophyll possess chloroplast and has two types of cells – palisade parenchyma and spongy parenchyma. Palisade parenchyma is made of elongated cells which are arranged vertically and parallel to each other. The spongy parenchyma cells are oval or round and loosely arranged. There are many large spaces and air-cavities between these cells. Vascular system includes vascular bundle. The vascular bundle are surrounded by a layer of thick walled bundle sheath cells.
Q.5. Compare the anatomy of an isobilateral or monocot leaf with a dicot leaf.
Ans :- The anatomy of an isobilateral leaf is similar to that of dorsiventral leaf. It shows the following differences. In an isobilateral leaf, the stomate are present on both the surface of the epidermis and the mesophyll is not differentiated into palisade and spongy parenchyma. In grasses, certain adaxial epidermal cells along the veins modify themselves into large, empty, colourless cells. These are called bulliform cells. When the bulliform cells in the leaves have absorbed water and are turgid, the leaf surface is exposed. When they are flaccid, due to water stress, they make the leaves curl inward to minimise the loss of water.
Q.6. Differentiate between :
(a) Meristematic tissue and permanent tissue.
(b) Isobilateral leaf and dorsiventral leaf.
(c) Heart wood and sap wood.
Ans :- (a) Meristematic tissue :-
(i) The tissue consisting of cells with the ability to divide is called meristematic.
(ii) It is present in grouping region i.e. apex of root and stem.
(iii) Cells are always living and walled.
(iv) It is responsible for growth and formation of permanent tissue.
(a) Permanent tissue :-
(i) The tissue consisting of cell without having the ability to divide is called permanent tissue.
(ii) It is present all throughout the plant body except growing region.
(iii) May be living or dead and thin walled.
(iv) It performs vital and mechanical function of the plant body.
(b) Isobilateral leaf :-
(i) The leaves arranged in an angular position to the ground are called iso.
(ii) Stomata are almost equally distributed on both the surfaces.
(iii) Upper and lower epidermis are structurally similar.
(iv) Mesophyll cells are not distinguishable.
(b) Dorsiventral leaf :-
(i) The leaves arranged parallel to the ground are called dorsiventral leaves.
(ii) Number of stomata is higher on the lower surface.
(iii) Upper and lower epidermis are structural dissimilar.
(iv) Mesophyll consists of spongy and palisade parenchyma.
(c) Heart wood :-
(i) The centrally located dark coloured region of the trunk of a tree is called heart wood.
(ii) It gives mechanical strength to the trunk.
(c) Sap wood :-
(i) The light coloured region of the trunk of a tree is called sap wood.
(ii) It is less durable as wood.
Q.7. What is periderm? How does periderm formation takes place in the dicot stem?
Ans :- Phellogen, phellem and phelloderm are collectively called periderm.
Periderm formation :-
As the stem continues to increase in birth due to the activity of vascular cambium, the outer cortical and epidermis layers get broken and need to be replaced to provide new protective cell layers. Hence, sooner or later, another meristematic tissue called cork cambium or phellogen develops, usually in the cortex region. Phellogen is made of narrow, thin walled rectangular cells. Phellogen cuts off cells on both sides. The outer cells differentiate into cork or phellem while the inner cell differentiate into secondary cortex or phelloderm. And cork is impervious to water due to suberin deposition in the cell wall. Phellogen, phellem and phelloderm are collectively known as periderm. Due to the activity of the cork cambium, pressure builds up on the remaining layers peripheral to the phellogen and ultimately these layers die and slough off.
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