6 ANATOMY OF FLOWERING PLANTS

CHAPTER NO.6 ANATONY OF FLOWERING PLANTS

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INTRODUCTION:TISSUES: Cells of plants exhibit great variation in size and structure.A group of cells performing essentially the same function and commonly of similar structure is called a tissue.

Depending upon the plant organ, various tissues are distributed in

characteristics patterns within the plant body.Plant Tissues are constituted of three basic types of systems.

1)Epidermal 2) Ground 3) Vascular

Let us discuss today Epidermal Tissue and Stomata:

EPIDERMIS: It is the outermost layer of all organs of primary plant body.sually,It is made up of single layer of cells. However in some plants it is multi-layered,Ex.Nerium.

The Epidermis of differs in origin, structure and function and called as epiblema layer.

It is made up of elongated, compactly arranged cells.Cells constituting epidermal cells are parenchymatous cells.

With little quantity of cytoplasm lining the cell wall with a large vacuole.The outer wall of epidermal cells contain a fatty substance called cutin and form cuticl on the epidermis. On the surface of cuticle, a waxy coating may also be present.

STOMATA:

These are the structures present in the epidermis of leaves.

Stomata help in gaseous exchange at the time of respiration and

photosynthesis.They are minute pores found on the epidermis of leaves, stem etc.Stomata transpiration takes place through stomata. They are two .dney shaped guard cells which bound a minute elliptical pore in a stoma.

The guard cells are modified epidermal cells. The wall of guard cells near the pore is thick. The outer wall is thin, elastic and semipermeable.In monocots the guard cells are Dumb-bell in outline.The guard cells are filled with chloroplasts.Both kidneys shaped and dumb-bell shaped guard cells have been reported in Cyperus.Average length of stomata is 20 micro meter to 28 micro meter and breadth 5 micrometer.

The opening and closing of stomata is controlled by guard cells.When water flows into the guard cells, they swell up and the curved surfaces cause the stomata to open.When the guard cells lose water, they shrink and become flacid and straight closing the stomata.

Part: AVERY SHORT ANSWER TYPE QUESTIONS:

(A).Multiple choice questions:

(i). The study of tissue is called...

(a). Biology

(b).Histology

(c).Microbiology

(d).Zoology

(ii).Group of cells which performs specific functions is called.....

(a). Tissue

(b).Neuron

(c).Cytoplasm

(d).Nephron

(iii). The tiny pores present on the epidermis layer of leaves which helps in exchange of gaseous called

(a).Lenticels

(b).Stomata

(c).Guard cells

(d).Nucleus

(iv). The outer wall of epidermal cells contains a fatty substance called....

(a). Cutin

(b).Melanin

(c). Cuticle

(d).None of above

(v).Epiblema of roots is equivalent to..

(a).Pericycle

(b).Endodermis

(c).Epidermis

(d).Stele

(B). State True or False:

(i). Study of tissue is called zoology.

(ii). Stomata help in gaseous exchange at the time of respiration and photosynthesis.

(C).Fill in the blanks.

(i). The outer wall of epidermal cells contain a fatty substance called.........

(ii). The opening and closing of stomata is controlled by..........

A. Multiple choice questions:

(i). (b) histology: study f tissue is called histology.

(ii). (a) tissue: group of cells is called tissue.

(iii). (b) stomata: tiny pores present on the epidermis layer of leaves.

(iv). (a) cutin: outer wall of epidermal cell, contains fatty substance

B.True or False.

(i). false: Study of tissue is called histology

(ii). True: Stomata help in exchange of gaseous.

C.Fill Up:

(i).Cutin

(ii).Guard cells

(B).Short Answer Type Questions:

1. Define the terms:

(a). Tissue.

(b).Stomata

2. Write short note on cause of opening and closing of stomata.

3. Plant Tissues are constituted of three basic types of systems, name them.Explain Epidermis.

4. Give the functions of guard cells, in plants.

(c).Long Answer Type Questions.

1. Draw a well labeled diagram of stomata. Which shows opening and _ closing of stomata. Also write the main functions of stomata.

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INTRODUCTION:Dear students you have read about different types of plant tissues. Lets now consider how tissues vary depending on their location in the plant body. Their structure and function would also be dependent on location. Today we will discuss about ground tissue system and vascular tissue system.

GROUND TISSUE SYSTEM: All tissues except epidermis and vascular bundles constitute Ground tissue.This system contains three cell types called parenchyma,collenchyma and sclerenchyma.

PARENCHYMA: Cells are found in all tissue types.They are living cells ,generally capable of further divisions, and have a thin primary cell wall. These cells have a variety of functions.The apical and lateral meristematic cells of shoots and roots provide the new cells required for growth.Food production and storage occurs in the photosynthetic cells of the leaf and stem called mesophyll cells, storage parenchyma cells form the bulk of most fruits and vegetables.

COLLENCHYMA: These are living cells similar to parenchyma cells, except that they have much thicker cell walls and are usually elongated and packed into long rope like fibres. They are capable of stretching and provide mechanical support in the ground tissue system of the elongating regions of the plant. Collenchyma cells are especially common in sub epidermal region of stem. Based on cell thickness and arrangement these are of four types; angular, annular, lamellar, and lacunar.

SCLERENCHYMA:Like collenchyma it has strengthening and supporting functions. However they are usually dead cells with thick lignified secondary cell walls that prevent them from stretching as the plant grows. Two common types are fibres,which often form long bundles and sclereids, which are shorter branched cells found in seed coat and fruit. Based on functions and morphology these are classified as under;

VASCULAR TISSUE SYSTEM: The phloem and the xylem together form a continuous vascular system throughout the plant In young plants they are usually associated with a variety of other cell types in vascular bundles. Both phloem and xylem are complex tissue. Their conducting elements are associated with parenchyma cells that maintain the elements and exchange materials with them. In addition, groups of collenchyma and sclerenchyma cells provide mechanical support.

In dicotyledonous stems cambium is present between phloem and xylem. Such vascular bundles are called open vascular bundles.In monocotyledons the vascular bundles have no cambium,hence these are called closed vascular bundles.

PHLOEM: Phloem is involved in the transport of organic salutes in the plant. The main conducting cells are aligned to form tubes called sieve tubes. The sieve tube elements at maturity are living cells, nterconnected perforations in their end walls formed from enlarged and modified plasmodesmata called sieve plates.These cells retain their plasma membrane, they have lost their nuclei and much of their cytoplasm.They therefore rely on associated companion cells for their maintenance. These companion cells have the additional function of actively transporting soluble food molecules into and out of sieve tube elements through porous sieve areas in the wall

XYLEM: Xylem carries water and dissolved ions in the plant. The main conducting cells are the vessel elements ,which are dead cells at maturity that lack a plasma membrane The cell wall has been secondarily thickened and heavily lignified. The vessel elements are closely associated with xylem parenchyma cells. which actively

transport selected solutes into and out of the elements across the parenchyma cell plasma membrane.the structural elements of xylem are tracheids, trachea, xylem fibre, xylem parenchyma and rays.

VASCULAR BUNDLES: Roots usually have a single vascular bundle, but dicot stems

have several bundles. These are arranged with strict radial symmetry in dicots but they are more irregularly dispersed in monocots.

Let us know what we have learnt

PART-A [VERY SHORT ANSWER TYPE QUESTIONS]

Multiple choice questions:

1. Food production and storage occurs in the photosynthetic cells of the leaf

and stem which are called as:

a) Xylem fibres

b) Mesophyll cells

c) Sieve plates

d) Both A and B

2. Angular type of cells are found in:

a) Xylem

b) Phloem

c) Collenchyma

d) Parenchyma

3. Vascular tissue system consists of:

a) Xylem

b) Phloem

c) Sclerenchyma

d) BothA andB

4. Plasmodesmata are found in:

a) Phloem

b) Xylem

c) BothA and B

d) None of these

5. Vascular bundles with strict radial symmetry are found in:

a) Dicot stem

b) Monocot stem

c) Parenchyma

d) None of these

Fill in the blanks:

1. All tissues except epidermis and vascular bundles constitute.........tissue

system.

2. Angular, annular, lamellar, and lacunar are types of................26

3. Tracheids are present in..................

True/False

1. Xylem carries water and dissolved ions in the plant.

2. Parenchyma, collenchyma and sclerenchyma form vascular tissue system.

3. Xylem parenchyma cells actively transport selected solutes into and out of

the elements across the parenchyma cell of plasma membrane.

ANSWER KEY: [PART-A]

A) Multiple choice questions:

1. a(Mesophyll cell are found in ground tissue-parenchyma)

2. c(collenchyma consists of four types of cells ,angular form is one of them)

3. d(Sclerenchyma is a ground tissue)

4. a(Sieve plates in phloem are also called plasmodesmata)

5. a(ln monocots these are irregularly dispersed)

B) Fill in the blanks:

1. Ground tissue

2. Collenchyma

3. Xylem

C) True/False:

1. True

2. False (Xylem and phloem form vascular tissue system)

3. True

PART-B [SHORT ANSWER TYPE QUESTIONS]

1. Write the types of sclerenchyma based on its function and morphology.

2. What are the structural elements of xylem?

3. What is the function of sclerenchyma cells?

PART-C [LONG ANSWER TYPE QUESTIONS]

1. Give an account of vascular tissue system in plants.

2. Write a note on ground tissue system in plants

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INTRODUCTION:Study of internal structure of the plants is known as ANATOMY.N.Grew, the father of plant anatomy was first to use term tissue.A tissue is group of cells having common, same method of development

and similar structure and function. The cells in a tissue may be all of one similar

type or of more than one dissimilar types. A tissue is formed in response to a

basic division of labour. Anatomy deais with internal organization of plants.

In plants Anatomy and Histology have same meaning.Tissues are classified into two types on the basis of stage of development:

MERISTEMATIC TISSUE

PERMANENT TISSUE We have already discussed in detail about different types of tissues in previous Daily Dose Assignments. Now let us discuss in detail about Anatomy of Monocot and Dicot Root.ANATOMY OF MONOCOT ROOT In transverse section, a monocot root (e.g Wheat, Maize) shows three zones:

1. Epidermal zone. It consists of epiblema. Cuticle is absent. It consists of single layer of thin walled cells. There are no intercellular spaces. Some of the

epiblema cells have tubular outgrowths called Root Hairs. The cells producing

root hair are called Trichoblasts. The epiblema is protective as well as bsorptive

in function.

2. Cortical zone. It is wider in monocot roots. It consists of parenchymatous

cortex. In older roots when epidermis disintegrates, outer layers of cortex

become thick walled and suberised to form exodermis for protection and

prevention of leakage of water. The innermost layer of cortex is called

endodermis made up of barrel shaped cells without intercellular spaces.

3. Stellar zone. It consists of single or multilayered pericycle from which

only lateral roots arise. Below it is 8 or more (polyarch condition)alternately and radially arranged xylem and phloem bundles and Parenchymatous Pith in the center.

ANATOMY OF DICOT ROOT In Transverse Section of Dicot Root (e.g. Gram, Sunflower, Tomato, Pea)shows three zones of tissues:

1. Epidermal zone , the outermost zone,consists of Epiblema (piliferous layer)or rhizodermis: Epidermis without cuticle and stomata, bearing unicellular root hairs and taking part in absorption of water is called epiblema. The cells are thin walled andtubular. The cells producing root hair are called Trichoblasts. Root

hairs are actually thin walled out growths of epidermal cells. This epiblema is

protective as well as absorptive in function.

2. Cortical zone. It consisting of thin walled parenchymatous, round oval or

angular cells forming cortex. Barrel shaped cells without intercellular spaces form Endodermis, the specialised innermost layer of cortex. Small but abundant intercellular spaces are present in cortex. Cortex is never sclerenchymatous in root. Endodermis bears Casparian strips on anticlinal walls on its cells. The cells of endodermis opposite to protoxylem are thin walled and without lignin, called passage or transfusion cells.

3. Stellar zone. Parenchymatous single layered Pericycle is present below

endodermis. It forms the outer boundary of stele or vascular strand. It forms

lateral roots, part of vascular cambium above xylem region and cork cambium by

Dedifferentiation. Vascular strand consists of 2-6 radial bundles each of xylem and phloem. Phloem bundles are in the form of small oval patches in contact with the pericycle. Xylem is Exarch as protoxylem is on the outer side in contact with the pericycle. Xylem bundles are four in Sun flower root, so Tetra arch. In between adjacent Xylem and Phloem, the conjunctive parenchyma is present.The different xylem bundles may come in contact centrally to form Metaxylem plate, and pith may be absent.

Let us know what we have learnt!

a) Multiple Choice questions:

1. In plants, anatomy is also called:

(a) Dendrochronology

(b) Histology

(d) internal cytology

2. Root Cap in dicots is formed from:

(a) Ground meristem

(b) Procambium

(d) Calyptrogen

3. Pericycle of Dicot root does not take part in formation of:

(a) Cambium

(b) Lateral roots

(d) Cork Cambium

4. Casparian strip occurs in the roots on radial walls of:

(a) Exodermis

(b) Passage cells

(d) Pericycle

5. Xylem vessel shows :

(a) Two way direction of flow of water

(b) One way direction of flow of water

(d) None of these.

b) Fill in the blanks:

1. is regarded as father of Plant Anatomy.

2. Xylem vessels are generally .

3. Cortex is very in monocot root.

c) True/False:

1. Root Cap is cushion of parenchymatous tissue for protection.

2. The root hairs are not derivatives of epidermal cells.

ANSWER KEY: PART-A

A) Multiple choice questions

1. b (Histology is the other name for anatomy)

2. c(In dicots the root cap is derived from the protoderm. )

3. c Pericycle of dicot root doesn't involves in formation of root hairs.

4. c Radial wall of Endodermis bears Casparian strips.

5. b ( Xylem vessels show only one way direction of flow of water)

B) Fill in the blanks

1. N. Grew

2. angular

3. wide

C) True/False

1. True

2. False (Epidemal cells are responsible for the origin of root hairs in the

roots of plants. )

1. Answer the following with refrence to the anatomy of dicot root:

(i) Where is the pericycle located?

(ii) How are the xylem vessels arranged?

(iii) What do you call such an arrangement?

2. Name the components of xylem. Which of these is suitable for

carrying water?

1. Draw a well labelled diagram of a typical monocot ROOT and explain

its different parts.

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INTRODUCTION:Different organs in plants show difference in their internal structure.Within angiosperms, the monocots and dicots are also seen to be

anatomically different. In the previous assignment we have discussed about anatomical structures of Monocot root and dicot root. Now we will study about the anatomy of both Dicot and Monocot stem.

DICOTYLEDONOUS STEM:Transverse sections of typical young dicot stem show:

1. EPIDERMIS: Outermost protective layer. It lacks chloroplast and is covered with thin layer of cuticle to reduce transpiration. Epidermis bears trichomes or stem hair and few stomata. Stomata contain kidney shaped (reniform) type guard cells. Guard cells have chloroplasts. Hair present is multicellular.

FUNCTIONS:

1. Being outermost, epidermis is protective.

2. Prevent entry of pathogens.

3. Cuticle reduce rate of transpiration.

4. Stomata take part in respiration.

2. HYPODERMIS: The cells arranged in multiple layers between epidermis and pericycle constitutes the cortex. It is divided in three zones.Outer one is hypodermis. It consists of few layers and collenchymatous cells just below the epidermis. It contains few chloroplasts. Hypodermis is absent or thin below stomata.

FUNCTIONS:

1. Provide flexibility as well as mechanical strength to young stem.

2. Collenchymatous hypodermis allows for elongation of young stem.

3. Due to presence of chioroplasts, it takes part in photosynthesis.

4. Cells have storage function.

3. GENERAL CORTEX: Below hypodermis, it is present in form of multilayered parenchymatous region. Cells are rounded and thin wailed.Intercellular spaces are present. Some outer cortical cells have chloroplast.

FUNCTIONS:

1. Storage of food.

2. Photosynthesis in outer layers of cortex.

3. Production of secretory minerals like oil and cortex.

4. ENDODERMIS: Its innermost layer of cortex. Cells are oval or barrel

shaped.Cells are oval or barrel shaped. Cells contain abundant starch grains.

Because of this reason endodermis in dicots is also called starch sheath. In

later stage, starch grains disappear.

FUNCTION:Cells perform storage function by storing starch.

5. PERICYCLE: It represents outer boundary of stele. Pericycle of dicot stem is 4-5 layered. It is homogenous and clerenchymatous in Cucurbita. In others, pericycle is heterogenous with semilunar sclerenchymatous patches over the vascular bundle and parenchymatous are as in between. The patches are also called bundle patches.

FUNCTIONS:

1. Sclerenchymatous pericycle has mechanical function.

2. Parenchymatous pericycle stores food and helps in lateral conduction of

food material.

6. VASCULAR STRAND: It consists of a ring of vascular bundles. The adjacent vascular bundles are separated by medullary rays. Such a vascular strand is called eustele. Vascular bundles are wedge shaped in outline with broader side towards the pericycle and narrower towards the centre. Each vascular bundle is conjoint, that is, it possesses both phloem and xylem.Vascular bundles are collateral with phloem lying on the outer side and xylem towards the inner side with both being present on the same radius. A strip of intrafascicular cambium occurs between phloem and xylem. Such vascular bundle is called open vascular bundle.Phloem is a vascular tissue that conducts organic nutrients. It consists of sieve tubes, companion cells, phloem parenchyma and a few phloem fibres.

Xylem is endarch with a clear distinction of protoxylem and metaxylem.

7. MEDULLARY RAYS: These are non vascular areas present in between the vascular bundles. It connects pith with pericycle and cortex.

8. MEDULLA OR PITH: It consist of central part of stem. It consists of

rounded, oval or polygonal parenchyma cells.

MONOCOTYLEDENOUS STEM Monocot stem possess only primary structure. It is usually circular in outline.The stem may be solid (maize) or fistular (grass). It doesn’t have differentiation of various components of ground tissue system. Vascular bundles are scattered.

1.EPIDERMIS: It is outer protective layer of living parenchymatous cells.Outer walls are cutinised and silicified. At places it bears stomata. Each stoma is surrounded by two dumbbell shaped guard cells, which contain chloroplast. Other epidermal cells are devoid of chloroplasts. Trichomes are

absent in monocots.

FUNCTIONS:

1. It provides protection to interior.

2. Silica gives stiffness as well as protection.

3. Cuticle checks the rate of surface transpiration.

4. Stomata allow exchange of gases as well as transpiration.

2. HYPODERMIS: It is outermost part of ground tissue. It lies inner to

epidermis. Monocot stem has clerenchymatous hypodermis. Below stomata, hypodermis is thin or absent.

FUNCTIONS:

1. It provides mechanical strength.

2. It acts as a heat screen.

3. GROUND TISSUE: It fills whole interior of the stem. There is no distinction of endodermis, pericycle, pith, or medullary rays. It is formed of thin walled parenchymatous cells. All the cells can store food. Some of outer cells may contain chloroplasts.

FUNCTIONS:

1. It provides turgidity to the soft stem.

2. Outer cells of ground tissue take part in photosynthesis.

3. It store food.

4. VASCULAR TISSUE: A large number of oval or rounded vascular bundles are seen. The vascular bundles occur scattered throughout the ground tissue. Such a vascular strand is called atactostele. Outer vascular

bundles are smaller as compared to inner ones. Each vascular bundle is surrounded by sheath of sclerenchyma known as bundle sheath. Each vascular bundle possesses both phloem and xylem. It is therefore conjoint.

Phloem lies towards the outer side while xylem lies towards the inner side on the same radius. Such vascular bundle is called collateral. Cambium is absent between xylem and phloem. Therefore the vascular bundles are closed. Phloem consist of both protophloem and metaphloem. Protophloem

is towards the outer side. Phioem lacks parenchyma.

FUNCTION:

Conduction of food (phloem) and conduction of water and minerals (xylem).

PART A: VERY SHORT ANSWER TYPE

A) MULTIPLE CHOICE QUESTIONS:

1. Trichomes are present in:

a) Monocot stem

b) Dicot stem

c) Both a) and b)

d) None of above

2. Hypodermis in monocot stem is formed of:

a) Collenchyma

b) Parenchyma

c) Sclerenchyma

d) None

3. Vascular bundles are closed if:

a) Cambium is present between phloem and xylem

b) Cambium is absent between phloem and xylem

c) Both are true

d) Both are false

4. Phloem lies towards the outer side of xylem on a same radius is known as:

a) Collateral

b) Conjoint

c) Open

d) Closed

5.Each vascular bundle is covered by sclerenchymatous bundles heath in:

a) Monocot stem

b) Dicot stem

c) Both

d) None

B) FILL IN THE BLANKS:

1) No distinction of cortex, endodermis, pericycle, pith or medullary rays

is seen in stem .

2) Vascular bundles are scattered throughout the ground tissue. Such

vascular strandiscalledas_ i.

3) Stomata are surrounded by type of guard cells in monocot stem.

C) TRUE OR FALSE:

1) Monocot stem possess numerous trichomes.

2) Vascular bundles are conjoint, collateral and open in dicot stems.

ANSWERS KEY: PART-A

A) MULTIPLE CHOICE QUESTIONS:

1. b) Trichomes are present in dicot stems.

2. c) Hypodermis is formed of sclerenchyma in monocots.

3. b) Vascular bundles are absent if cambium is absent.

4. a) In collateral bundles, phloem is present on outer and xylem

on inner side.

5. b) In dicots, vascular bundles are covered by sclerenchymatous bundle sheath.

B) FILL IN THE BLANKS:

1.Monocot

2. Atactostele

3. Dumb bell

C)TRUE / FALSE:

1. False. (Trichomes are present on dicot stems)

2. True

PART B: SHORT ANSWER TYPE QUESTIONS:

1. What are main functions of epidermis in stem?

2. Endodermis in dicot stem is also known as a starch sheath. Why?

3. Discuss vascular bundles in dicot stems.

4. Draw a labelled diagram of dicot stem.

PART C: VERY SHORT ANSWER TYPE QUESTIONS:

1. What are major anatomical differences in monocot and dicot stems?

2. Discuss the detailed anatomical structure of a monocot stem. Support

your answer with a well labelled diagram.

A69

INTRODUCTION:

ANATOMY OF LEAF:Normally when we talk of a leaf, we mean a foliage leaf is characterized by green colour, thinness and flatness. The foliage leaves are lateral

appendages of a limited growth. They are very important vegetative organs and chiefly concerned with the physiological process like photosynthesis and transpiration.On the basis of mesophyll the foliage are two types:

1. DORSIVENTRAL LEAF

2. ISOBILATERAL LEAF

|. lIsobilateral Leaf: Mesophyll tissue is not differentiated and having same type of cells on both adaxial and abaxial surfaces. These are commonly found in onocotyledonous plants.

li. Dorsiventral Leaf: In this the mesophyll tissues are differentiated into

palisade parenchyma and spongy parenchyma. It is very common in the Dicotyledonous plants.

ANATOMY OF MONOCOT LEAF

(i) Epidermis: a. Monocot leaf has upper and lower epidermis. =2.02:2

b. Cuticle is present on the outer wall stomata are present on both upper and lower epidermis. Some cells of upper epidermis are large and thin walled they are known

AS ote es,

(ii) Mesophyll:

a. Itis the ground tissue that is present between both epidermal layers.

b. Mesophyll is not differentiated into palisade and spongy parenchyma. The cells

are irregularly arranged with inter-cellular spaces.

(iii) Vascular bundles:

a. Large number of vascular bundles are present, some of which are small and

some are large.

b.Vascular bundles are conjoint, collateral and closed. Xylem is present towards

upper epidermis and phloem towards lower epidermis. Phloem consists sieve tubes and companion cells. Xylem is formed of vessels, tracheids and xylem parenchyma.

In Maize leaf the undifferentiated mesophyll occurs in concentric layers

around vascular bundles having large centrifugal chloroplasts in its large

bundle sheath cells. Such an arrangement is called .

ANATOMY OF DICOT LEAF

(i) Epidermis:

a. A dicotyledonous leaf is usually .

b. Ithas upper epidermis and lower epidermis. The epidermis is generally formed of a single layer of cells which are packed closely.

c. The cuticle on the upper epidermis is thicker as compared to the lower

epidermis.

d. The minute openings that found on the epidermis are termed as stomata. The

numbers of stomata are more on the upper surface epidermis as compared to the

lower epidermis.

(ii) Mesophyll:

a. The entire tissue among the upper and lower epidermis is termed as the

mesophyll.

b. In the mesophyll there are 2 regions. They are spongy parenchyma and

palisade parenchyma.

c. Palisade parenchyma cells are observed below the upper epidermis. It contains

vertically elongated cylindrical cells in one or more than one layers. These cells are efficiently arranged with no intercellular spaces. The task of palisade parenchyma is photosynthesis.

d. Spongy parenchyma takes place below the palisade parenchyma. Spongy cells

are unevenly shaped. These cells are arranged very loosely along with several

airspaces.

e. The air space which is found next to the stoma is termed as respiratory cavity.

(iv) Vascular tissues:

a. These exist in the veins of leaf. VASCULAR BUNDLES are collateral ,conjoint.

b. Xylem exists in the direction of the upper epidermis; where else the phloem is in the direction of the lower epidermis.

c.termed as Bundle sheath. Phloem contains sieve tubes, phloem parenchyma and companion cells. Phloem fibers are not present. Xyiem contains vessels and

xylem parenchyma. Tracheids and xylem fibers are not present.

PART: A_VERY SHORT ANSWER TYPE QUESTIONS:

|. MULTIPLE CHOICE QUESTIONS:

1. Dicotyledonous plans have:

a) Palisade parenchyma

b) Spongy parenchyma

c) Both (a) & (b)

d) None of the above

2. Leaves are:

a) Vegetative organs

b) Reproductive organs

c) Both (a) & (b)

d) None of the above

3. Vascular Bundles in monocot leaf are:

a) Conjoint and closed

b) Conjoint and open

c) Radial and closed

d) None of the above

4. The epidermis which covers upper surface of leaf is called:

a) Abascial epidermis

b) Adaxial epidermis

c) Both (a) & (b)

d) None of the above

5. Monocotyledonous leaves are:

a) lsobilateral

b) Dorsiventral

c) Both (a) & (b)

d) None of the above

ll. Fill in the blanks:

1. Number of stomata is on the upper epidermis.

2. Dicot leaf show and type of vascular bundle.

3. cells are present in the upper epidermis of monocot leaf.

III. State True or False:

1. Mesophyll in dicot leaf is differentiated into palisade and spongy

parenchyma.

2. Spongy parenchyma consists of loosely arranged irregularly shaped

cells.

ANSWER KEY: PART-A

l. MULTIPLE CHOICE QUESTIONS:

1. c- Mesophyll have both spongy and palisade parenchyma.

2. a — Vegetative parts of plants.

3. a— Vascular bundle are conjoint and closed type.

4. b —-Adaxial epidermis

5. c - lsobilateral

ll. Fill in the blanks:

1. more

2. conjoint and collateral

3. Bulliform

Ill. State True or False:

1. True

2. True

PART: B SHORT ANSWER TYPE QUESTIONS:

1. Give difference between dicot and monocot leaf?

2. Briefly describe the vascular bundles in monocot leaf?

PART: C LONG ANSWER TYPE QUESTIONS:

1. Draw a well labeled diagram of V.S. of dicot leaf.

A70

INTRODUCTION:The increase in thickness or girth due to the activity of cambium and

the cork cambium is known as secondary growth.Secondary growth results from the activity of two meristem tissue

1. vascular cambium

2. Cork cambium: It occurs in the root and stem of gymnosperms and dicots.

Secondary growth in dicot stem completes in following steps:

1. Formation of vascular cambium ring:

(i)Intrafascicular cambium: It is primary in origin, present in between primary phloem and primary xylem. At the time of secondary growth, it becomes functionally a secondary meristem

(ii) Interfascicular cambium.:it is true secondary meristem. It originates from parenchyma cells of medullary rays region. It lies in between the vascular bundles.

(iii) Vascular cambium ring: Both intrafascicular and interfascicular cambia join each other and forms cambium ring.

The cambial ring becomes active and begins to cut off new cells, both towards the inner and the outer sides.The cells cut off towards pith, mature into secondary xylem and the cells cut off towards periphery mature into secondary phloem The cambium is generally more active on the inner side than on the outer.As a result, the amount of secondary xylem produced is more than secondary phloem and soon forms a compact mass.The primary and secondary phloems get gradually crushed due to the continued formation and accumulation of secondary xylem.The primary xylem however remains more or less intact, in or around the centre.At some places, the cambium forms a narrow band of parenchyma,

which passes through the secondary xylem and the secondary phloem in the radial directions. These are the secondary medullary rays.

These are formed by the seasonal activity of vascular cambium.

Cambium is not uniformly active throughout the year.In spring or summer cambium is more active and forms large sized xylem elements (vessels) which constitute spring or early wood.in autumn or winter, cambium is less active and cut off small sized

xylem elements (vessels) and constitute autumn wood or late wood.Both autumn and spring wood constitute an annual ring.

In one year, only one annual ring is formed.In successive years numerous growth rings are formed.Thus, by counting the number of annual rings in the main stem at the base we can determine the age of a tree.This branch of science is known as dendrochronology.Growth rings are distinct or sharply demarcated in the plants of

temperate climate, eg. Shimla, Nainital, Mussourie due to presence of contrasting seasonal variations.Growth rings are not distinct or sharply demarcated in the trees of tropical climate (near equator), e.g. Calcutta, Bombay, Madras due to

absence of contrasting seasonal variations.

Formation of cork cambium:

1. It is formed by dedifferentiation of cortical cells. It is also called as

phellogen. It is made of narrow thin-walled and nearly rectangular cells.

2. Phellogen cuts cells on both sides. Towards inner side, it forms

Rn Which is living and paranchymatous.

Towards outer side, it forms cork or phellem. It is impervious to water.

3. Phellem + Phellogen + Phelloderm = Periderm

(Outer protective secondary tissue).

BARK OF TREE

BARK: It is a non-technical term that refers to all tissues lying outside the

vascular cambium.It includes periderm and secondary phloem.

(a) Bark formed early in the season is called early or soft bark.

(b) Towards the end of the season late or hard bark is formed

LENTICELS: At some places phellogen cuts off closely arranged parenchymatous cells on the outer side instead of cork cells. These parenchymatous cells soon rupture the epidermis forming lens-shape opening called lenticels. These parenchymatous cells are called complimentary cells.

BARK: SHOWING LENTICELS It helps in exchange of gases.It is generally present in woody stem.Vascular bundles in dicot root are radial, exarch and mostly triarch.

Vascular cambium is formed secondarily from conjuctive parenchyma cells lying just below each phioem strand. Thus, the number of cambium strips formed equals the number of phloem strands.The cells of pericycle lying outside the protoxylem also become

meristematic to form part of strips of cambium.These cambial strips join the first formed cambium strips to form complete but wavy ring of vascular cambium.This cambium ring produces secondary xylem on inner side and secondary phloem on outer side.In roots, the growth rings are not distinct because there is no seasonal variation under the soil.From the outer layers of pericycle arises the phellogen which cuts

phellem (cork) on the outerside and secondary cortex or phelloderm

toward the inner side

LET US KNOW WHAT WE HAVE LEARNT!

PART-A VERY SHORT ANSWER TYPE QUESTIONS:

A. MCQs:

1. Secondary medullary rays are produced by:

(a) Fusiform initial

(b) Interfasicular cambium

(d) Ray Initial

2. What is the position of oldest secondary phloem:

(a) Just outside the pericycle

(b) Just outside the vascular cambium

(d) Below the vascular cambium

3. Heart wood is

(a) Situated away from vascular cambium

(b) Situated near pith

(d) All of these

4. In cork are meant for gaseous exchange.

(a) Stomata

(b) Lenticels

(d) Hydathodes

5. Cork cambium is:

(a) Periderm

(b) Phellem

(d) Phellogen

B. FILL IN THE BLANKS:

1. Secondary Phloem is formed by .

2. In Leaf Anatomy, Phloem is directed towards .

3. Heartwoodis sin color.

C. TRUE/FALSE:

1. Heart wood is more hard durable and resistant to the attack of micro-

organisms and insects.

2. Cork Cambium is called Complimentary Cells.

ANSWER KEY: PART -A

A. MCQs:

1.(b) Interfasicular cambium(They are formed by activity of fasicular

cambium)

2. (b) Just outside the vascular cambium. (the position of oldest secondary

phloem is Just outside the vascular cambium)

3. (b) Situated near pith. (Heart wood isSituated near pith& forms the

central major portion)

4. (b) Lenticels(In cork Lenticelsare meant for gaseous exchange)

5. (d) Phellogen(Cork cambium is also called as Phellogen)

B. FILL Ups:

1. vascular cambium

2. lower surface

3. brown

C. TRUE/FALSE:

1. True

2. False (Cork cambium is also called as Phellogen)

PART -B SHORT ANSWER TYPE QUESTIONS

1. How annual rings are formed?

2. How is cambial ring formed in dicot stem?

PART-C LONG ANSWER TYPE QUESTIONS

1. Describe the process of secondary growth in Dicot Stem.

A71

RECAPITULATION:Dear students in the chapter ‘Anatomy of flowering plants ‘.you have read all the topics in detail. As this chapter deals with the internal structure of plants, We have learnt that Plants have cells as the basic unit, cells are organized into tissues and in turn the tissues are organized into organs. Different organs in a plant show

difference in their structure. Now let us do NCERT book questions;

2. Cork cambium forms tissues that form the cork. Do you agree with this statement? Explain.

ANS. Yes, cork cambium forms tissues that in turn form the [J When the stem

increases in girth, another meristematic tissue known as phellogen or cork

cambium grows in the cortex region of the stem. This phellogen cuts off cells on

both of the sides. The outer cells differentiate into the [MM or the cork while the inner cells differentiate into the EM or secondary cortex. The cork is

impermeable to water because of suberin, rendering protection to the tissues

undemeath.

3. Explain the process of secondary growth in the stems of woody angiosperms with the help of schematic diagrams. What is its significance?

ANS. The primary xylem and phloem exhibits the presence of a strip of cambium

in woody dicot roots known as the interfascicular cambium which is formed from the cells of the medullary rays connecting the interfascicular cambium. Hence, the continuous cambium ring is formed. The cambium separates from the newly formed celis on either side while the cells found towards the exterior differentiate into the secondary phloem. The cells detach towards the pith giving rise to the secondary xylem. The secondary xylem is synthesized in excess compared to the secondary phloem. When there is secondary growth in plants, the girth of the

plants increase, along with an increase in the water content and nutrients in order

to assist the ever growing leaves, rendering support to the plants.

6. The transverse section of a plant material shows the following anatomical

features (a) the vascular bundles are conjoint, scattered and surrounded by sclerenchymatous bundle sheaths.

(b) phloem parenchyma is absent. What will you identify it as?

ANS. The transverse section is of Monocot stem. It is because the vascular

bundles are dispersed in monocot stems. The phloem parenchyma is not found.

7. Why are xylem and phloem called complex tissues?

ANS. Xylem and Phioem are called complex tissues because they are made of more than one type of cells which work together as a unit to perform the function.Xylem transports water while phloem transports food.

8. What is a stomatal apparatus? Explain the structure of stomata with a

labelled diagram.

ANS. Stomata are structures present in the epidermis of leaves. Stomata regulate

the process of transpiration and gaseous exchange. Each stoma is composed of

two bean-shaped cells known as guard cells which enclose stomatal pore. Guard cells are dumbbell-shaped, where its outer wall is thin and inner wall is highly thickened. These structures possess chloroplasts and regulate the closing

and opening of the stomata. The epidermal cells near the guard cells in some cases become specialized in their structure, shape and size; they are referred to as subsidiary cells. The guard-cells, the stomatal aperture and girdling subsidiary cells are collectively referred toas stomatal apparatus.

9. Name the three basic tissue systems in the flowering plants. Give the tissue names under each system.

ANS. Following are the three basic tissue systems in the flowering plants.Epidermal tissue system Epidermal tissue system includes epidermis and epidermal appendages.Epidermis comprises epidermal cells and guard cells while the epidermal

appendages include root hair, stem hair, stinging hair and glandular hair.The qround tissue system Ground tissue system is made up of simple tissues such as parenchyma,

collenchyma and sclerenchyma.Vascular tissue system Vascular tissue system consists of complex tissues such as Xylem, phloem and vascular cambium.

10. How is the study of plant anatomy useful to us?

ANS. ie BEE Physiological conditions can be studied, which helps in crop improvement. Study of plant fibres such as flax, jute etc. helps in their commercial

exploitation as it enables them to predict the strength of wood which can be utilized

to its potential.

11. What is periderm? How does periderm formation take place in the dicot

stems?

ANS. Phetieges; EE and phelloderm are collectively known as periderm.While plants undergo secondary growth, the outer epidermal layer and the cortical layer are ripped due to cambium. In order to replace them, the cortex ceils tum meristematic which produces the cork cambium or the phellogen which comprises thin-walled, narrow and rectangular cells. The phellogen sheds cells on either side.cork The cells which shed from the exterior give rise to the or phellem. The suberin accumulates in its cell wail making it impermeable to water while the inner cellsemerge to become the secondary cortex or phelloderm which is parenchymatous.

12. Describe the internal structure of a dorsiventral leaf with the help of

labelled diagram.

ANS. Dicots exhibit dorsiventral leaves. When examined, the vertical section

of a dorsiventral leaf consists of three different parts, they are:

Epidermis — it is found on the adaxial epidermis (upper surface) and the abaxial epidermis (lower surface). On the outside, the epidermis is covered with a thick cuticle. Compared to the upper surface, the abaxial epidermis comprises more stomata.

Mesophylil - 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 is composed of tall,compactly-arranged cells while the spongy parenchyma comprises round or oval, loosely-arranged cells possessing intercellular spaces. The mesophyll comprises chloroplasts that carry out photosynthesis.

Vascular system — The vascular bundles that are found in leaves are closed and conjoint which are engirdied by thick layers of bundle-sheath cells.

A72

RECAPITULATION:Dear students, earlier you have studied Anatomy of flowering plants. Today we will revise all important diagrams from chapter 6 — Anatomy of flowering plants.

THE TISSUE:-A Tissue is a group of cells having a common origin and usually performing common function.

TYPES OF PLANT TISSUE

1. MERISTEMATIC TISSUE:- Cells are capable of cell division.

APICAL MERISTEM: - FOUND AT THE TIPS ON THE SHOOT AND ROOTS.

2. PERMANENT TISSUE: - Incapable of cell division, long lasting tissue which have mature cell.

SIMPLE TISSUE: - Made of only one type of cells.

COMPLEX TISSUE: - Made of more than one type of cells.

PART -A VERY SHORT ANSWER TYPE QUESTIONS:

1. The most common ground tissue in plant is:

a) Epidermis

b) Cortex

c) Parenchyma

d) Collenchymas

2. The outer wall of epidermal cells contains a fatty substance called:

a) Cutin

b) Melanin

c) Cuticle

d) None of these

3. Vascular tissue system consists of

a) Xylem

b) Phloem

c) Sclerenchyma

d) Both a and b

4.Root cap in dicots is formed from

a) Ground meristem

b) Procambium

c) Protoderm

d) Calyptrogens

5.Each vascular bundle is covered by sclerenchyma bundle sheath in

a) Monocot stem

b) Dicot stem

c) Both

d) None

B.Fill in the blanks:

1. Internal plant organisation is studied under .

2. Dicot leaf show and type of vascular bundles.

3. is regarded as father of plant anantomy.

C. TRUE/FALSE

1.Study of tissue is called HISTOGRAM.

2. Parenchyma ,collenchyma,sclerenchyma form vascular tissue system.

3.Roots cap is cushion of parenchymatous tissue for protection.

ANSWER KEY: PART -A

MCQs

1. (c) Parenchyma most common ground tissue.

2. (c) Cutin outer wall of epidermal cells contain fatty substances.

3. (d) sclerenchyma is a ground tissue.

4. (c) In dicots the root cap is derived from the protoderm.

5. (b) In dicots vascular bundles are covered by sclerenchymatous bundle sheath.

B.Fill in the blanks:

1. Anatomy

2. Conjoint and Collateral

3. N. Grew

C. TRUE/FALSE

1. False (study of tissue is called HISTOLOGY.

2. False (xylem and phloem form vascular tissue system).

3. True

PART-B SHORT ANSWER TYPE QUESTIONS

1. Name the component of xylem which of these is suitable for carrying

water?

2. What is the function of sclerenchyma cells?

3. Give the differences between Dicot and Monocot roots.

PART-C LONG ANSWER TYPE QUESTIONS

1. Draw a well labelled diagram of stomata which shows opening and closing

of stomata. Also write the main functions of stomata.

2. Draw a well labelled diagram of a typical monocot root and explain its

different parts.

Chapter 6 Anatomy Of Flowering Plants

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Friday 5 February 2021

Chapter 6 Anatomy Of Flowering Plants

Chapter 6 Anatomy Of Flowering Plants

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