NCERT Exemplar class 11 Biology Solutions  Anatomy of Flowering Plants

Multiple Choice Questions
1.A transverse section of stem is stained first with safranin and then with fast green following the usual schedule of double staining for the preparation of a permanent slide. What would be the colour of the stained xylem and phloem?
(a) Red and green
(b) Green and red
(c) Orange and yellow
(d) Purple and orange
Soln. (a)

2.Match the followings and choose the correct option from below.
A.Meristem              (i) Photosynthesis,  storage
B.Parenchyma         (ii) Mechanical support
C.Collenchyma        (iii) Actively dividing cells
D.Sclerenchyma      (iv) Stomata
E.Epidermal tissue  (v) Sdereids Options:
(a) A-(i), B-(iii), C-(v), D-(ii), E-(iv)
(b) Ar(iii), B-(i), C-(ii), D-(v), E-(iv)
(c) A-(ii), B-(iv), C-(v), D-(i), E-(iii)
(d) A-(v), B-(iv), C-(iii),D-(ii), E-(i)
Soln. (b)

3.Match the following and choose the correct option from below.
A.Cuticle                            (i)Guard cells
B.Bulliform cells           (ii)Single layer
C.Stomata                       (iii)Waxy layer
D.Epidermis                  (iv)Empty colourless cell
(a) A-(iii), B-(iv), C-(i),   D-(ii)
(b) A-(i),    B-(ii), C-(iii), D-(iv)
(c) A-(iii),  B-(ii), C-(iv), D-(i)
(d) A-(iii),  B-(ii), C-(i),   D-(iv)  
Soln. (a)

4.Identify the simple tissue from among the following.
(a) Parenchyma (b) Xylem
(c) Epidermis (d) Phloem
Soln. (a): Parenchyma is a simple permanent tissue found in plants whereas, xylem and phloem are complex permanent tissues. Epidermis is a part of epidermal tissue system.

5.Cells of this tissue are living and show angular wall thickening. They also provide mechanical support. The tissue is
(a) xylem (b) sclerenchyma
(c) collenchyma (d) epidermis.

6.Epiblema of roots is equivalent to
(a) pericycle (b) endodermis
(c) epidermis (d) stele.
Soln. (c): Epiblema or piliferous layer (rhizodermis) is the outermost layer of young root which has thin-walled cells. Some of the cells give rise to root hairs which take part in the absorption of water and mineral salts. Epidermis is also outermost layer. Therefore epiblema-of root is equivalent to epidermis. Pericycle is believed to represent the outer boundary of vascular strands. A part of vascular cambium and cork cambium develop from pericycle. Endodermis is the innermost layer of the cortex. All tissues on the inner side of the endodermis constitute stele.

7.A conjoint and open vascular bundle will be observed in the transverse section of
(a) monocot root (b) monocot stem (c) dicot root (d) dicot stem.
Soln. (d) : Vascular bundles which contain both xylem and phloem are called conjoint vascular bundles. In gymnosperms and dicot stems vascular bundles contain both xylem, phloem and a strip of vascular cambium (between phloem and xylem of each vascular buncjje) called intrafascicular (or fascicular) cambium. It produces secondary tissues. Such vascular bundles are described as open because the original or primary phloem and xylem separate on the production of secondary tissues by vascular cambium. Thus, conjoint and open vascular bundles will be observed in dicot stem.

8. Interfascicular cambium and cork cambium are formed due to
(a) cell division
(b) cell differentiation
(c) cell dedifferentiation
(d) redifferentiation.
Soln. (c): The phenomenon of regeneration of permanent tissue to become meristematic is called dedifferentiation. Cork cambium, wound cambium and interfascicular vascular cambium are the examples of secondary meristems which are always produced through dedifferentiation.

9.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.
Soln. (b): Cork cambium is also called phellogen. The tissue of cork cells is called as cork or phellem.

10.In which of the following pairs of parts of a flowering plant is epidermis absent?
(a) Root tip and shoot tip
(b) Shoot bud and floral bud
(c) Ovule and seed
(d) Petiole and pedicel Maim
11.How many shoot apical meristems are likely to be present in a twig of a plant possessing, 4 branches and 26 leaves?
(a) 26 (b) 1
(c) 5 (d) 30
(e) 4
Soln.(c): The shoot apical meristems are present at the tips of the stem, and its branches. They produce growth in length. As the twig possesses 4 branches, number of shoot apical meristems are likely to be 5 including one of the twig itself.

12.A piece of wood having no vessels (trachea) must be belonging to
(a) teak (b) mango
(c) pine (d) palm.
Soln.(c): Vessels are absent in gymnosperms and pteridophytes with the exceptions of a few e.g., Selaginella, Gnetnm. Presence of vessels is a characteristic feature of angiosperms. Out of the given options, teak, mango and palm are angiosperms, thus they will contain vessels.

13.A plant tissue, when stained, showed the presence of hemicellulose and pectin in cell wall of its cells. The tissue represents
(a) collenchyma (b) sclerenchyma
(c) xylem (d) meristem.
Soln.(a): Walls of collenchyma are thick, often the thickening is unevenly distributed. They contain in addition to cellulose (20%), large amounts of pectin (45%) and hemicellulose (35%) but no lignin. They are never lignified.

14.In conifers, fibres are likely to be absent in
(a) secondary phloem (b) secondary xylem
(c) primary phloem (d) leaves.
Soln. (b): Fibres occur in all those parts where mechanical strength is required i.e., leaves, petioles, cortex, xylem, phloem, etc. In conifers, they are likely to be absent in secondary xylem.

15.When we peel the skin of a potato tuber, we remove
(a) periderm (b) epidermis
(c) cuticle (d) sapwood.
Soln. (a): Periderm is a tissue of secondary origin that replaces damaged epidermis. It can be found in underground plant organs. In potato, a model for periderm studies, periderm replaces the epidermis early in tuber development and suberized phellems constitute tuber’s skin. Thus when we peel off a potato tuber we will remove periderm.

16.A vessel less piece of stem possessing prominent sieve tubes would belong to
(a) Pinus (b) Eucalyptus
(c) Grass (d) Trochodendron.
Soln. (d)

17.Which one of the following cell types always divides by anticlinal cell division?
(a) Fusiform initial cells (b) Root cap (c) Protoderm (d) Phellogen .
Soln. (c)

18.What is the fate of primary xylem in a dicot root showing extensive secondary growth?
(a) It is retained in the centre of the axis.
(b) It gets crushed.
(c) May or may not get crushed.
(d) If gets surrounded by primary phloem.
Soln. (a): The cambial ring becomes active and begins to cut off new cells, both towards the inner and outer sides. The cells cut off ‘ towards pith, mature into secondary xylem and the cells cut off towards periphery mature into secondary phloem. 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.

Short Answer Type Questions
1.Product of photosynthesis is transported from the leaves to various parts of the plants and stored in some cell before being utilised. What are the cells/ tissues that store them?
Soln. The food gets stored in specialised parenchymatous cells present either in roots or stems.

2.Protoxylem is the first formed xylem. If the protoxylem lies next to phloem what kind of arrangement of xylem would you call it?
Soln. If protoxylem lies next to the phloem, this arrangement of xylem is called exarch.

3.What is,the function of phloem parenchyma?
Soln. Phloem parenchyma stores food materials and help in transport of food.

4.What is present on the surface of the leaves which helps the plant prevent loss of water but is absent in roots?
Soln. Thick waxy layer called cuticle is present on the surface of the leaves which helps the plant to prevent loss of water. It is absent in roots.

5.What is the epidermal cell modification in plants which prevents water loss?
Soln. The upper or adaxial epidermis of monocot leaves contains groups of large thin-walled protruding and turgid cells over the regions of veins, called bulliform cells. Bulliform cells bring about rolling of leaves during dry season. In case of water deficiency they lose water and become flaccid thus bringing about rolling of leaves reducing exposed surface thereby transpiration.

6.Which part of the plant would show the following:
(a) Radial vascular bundle
(b) Polyarch xylem
(c) Well developed pith
Soln. (a) Roots show radial vascular bundle.
(b) Monocot roots show polyarch xylem.
(c) Dicotyledonous stems and mono- cotyledonous roots show well developed pith.

7.What are the cells that make the leaves curl in plants during water stress?
Soln. Bulliform cells present in the upper epidermis of monocot leaves, make the leaves curl in plants during water stress.

8.What constitutes the cambial ring?
Soln. Ring of vascular cambium (cambial ring) is formed by two types of meristems, fascicular or intrafascicular and interfascicular cambium.
Intrafascicular cambium is a primary meristem which occurs as strips in vascular bundles. Interfascicular cambium is a secondary meristem which arises from the cells of medullary rays which occur at the level of intrafascicular strips. The two types of meristematic tissues get connected to form a cambial ring.

9.Give one basic functional difference between phellogen and phelloderm.
Soln. Phellogen is a meristematic tissue whereas phelloderm is permanent tissue. Phellogen is a secondary lateral meristem that may arise from permanent living cells of cortex. The cells divide in a tangential plane cutting cells towards the inner as well as outer side which form phelloderm as well as phellem. Phelloderm cells are living and possess cellulose cell wall. In some species these cells may contain chloroplast and starch.

10.Arrange the following in the sequence you would find them in a plant starting from the periphery – phellem, phellogen, phelloderm.
Soln. Phellem or cork is outermost layer, followed by phellogen (cork cambium) which in turn is followed by phelloderm (secondary cortex).

11.If one debarks a tree, what parts of the plant is being removed?
Soln. Debark means removal of bark. In common language and economic botany all dead cells lying outside phellogen are collectively called bark [In anatomical usage, bark includes all tissues outside vascular cambium. It is then differentiated into outer bark or rhytidome (consisting of dead cells) and inner bark (or living cells, i.e. periderm and secondary phloem)]. The outer layers of the bark are constantly peeled off on account of formation of new secondary vascular tissues in the interior.

12.The cross-section of a plant material showed the following features when viewed under the microscope.
(a) The vascular bundles were radially arranged.
(b) Four xylem strands with exarch condition of protoxylem.
To which organ should it be assigned?
Soln. Cross section of dicot roots show vascular bundles arranged radially. Four xylem strands with exarch condition of protoxylem are found here.

13. Wha do hardwood and softwood stand for?
Soln. Hardwood is the nameofdicotwood. The wood contains vessels and is therefore called porous wood. The content of the tracheids is very low (less than 5%). Wood or xylem fibres are abundant. The wood is comparatively difficult to work with. Softwood is the name of gymnospermous wood. This wood is devoid of vessels therefore, also called non- porous wood. The content of tracheids can be 90-95%. Wood or xylem fibres are fewer and the wood is easy to work with.

Short Answer Type Questions
1.While eating peach or pear it is usually seen that some stone like structures get entangled in the teeth, what are these stone like structures called?
Soln. The stone like structures get entangled in the teeth while eating peach or pear. These are stone cells or sclereids. They are highly thickened dead sclerenchyma cells with very narrow cavities which provide stiffness to the parts in which they occur.

2.What is the commercial source of cork? How is it formed in the plant?
Soln. The phellem (cork) of Quercus suber (cork oak) is the source of commercial cork. In this plant first phellogen in the stem arises in the epidermis. This phellogen persists on the plant indefinitely but when the tree is about twenty years old the first formed periderm, known as virgin cork, is removed. Then a new layer of phellogen is formed deeper in the cortex which forms cork more rapidly. This cork is removed after about ten years when it is sufficiently thick to be of commercial value. Subsequent strippings are made at intervals of above ten years until the tree has attained the age of 150 years or more. Cork has thin walled cells with lumina filled with air. Its light weight, resistance to pressure, acids and other chemical, thermal insulating qualities and imperviousness to liquid make it commercially important.

3.Below is a list of plant fibres. From which part of the plant these are obtained?
(a) Coir
(b) Hemp
(c) Cotton
(d) Jute
Soln. (a) Coir is a natural fibre obtained from husk of coconut. It is the fibrous mesocarp of coconut fruit Cocos nucifem.
(b) Hemp is fibre obtained from pericycle of Cannabis sativa.
(c) Cotton (Gossypium species) is a surface fibre i.e., fibres arise from seed coat.
(d) Jute (Corchorus capsularis and Corchorus olitorius) is a bast fibre obtained from the secondary phloem.

4.What are the characteristic differences found in the vascular tissue of gymnosperms and angiosperms?
Soln. Characteristic differences found in the vascular tissues of gymnosperms and angiosperms are as follows:
(i) Xylem of angiospermic vascular bundles are composed of four different kinds of elements namely tracheids, vessels, xylem fibres and xylem parenchyma whereas xylem of gymnospermic vascular bundles ‘ are devoid of vessels.
(ii)Phloem of angiospermic vascular bundles are composed of sieve tube elements, companion cells, phloem parenchyma and phloem fibres whereas gymnospermic vascular bundles lack sieve tubes and companion cells.

5.Epidermal cells are often modified to perform specialised functions in plants. Name some of them and function they perform.
Soln. Some epidermal cells are often modified to perform specialised functions in plant. These are discussed as follows:
(I) Trichomes: They are unicellular or
multicellular outgrowths which are strictly epidermal in origin. Trichomes are of two kinds, hair and scales. Hair are elongated structures and can be unicellular or multicellular. Scales are multicellular flattened structures.
(i) Root hairs: They are unicellular tubular structures found in epiblema of root in a special area called root hair zone. Root hair are enlargement of epiblema cells. They have vacuolated protoplasm and they are ephemeral. Nucleus occurs towards the apical part of the hair. They take part in absorption of water and mineral salts. They hold soil particles and play an important role in anchoring the plants.
(ii) Aerial hairs: They are unicellular or multicellular appendages which are covered by a layer of cuticle. They enclose stationary air and protect the plant organs against sudden changes of temperature and high rate of transpiration.
(iii) Stinging hairs: They are hollow hairs that contain siliceous tips and enclose poison. They protect the plant from herbivores.
(iv) Glandular hairs: Most of the glandular trichomes produce essential oils. They provide aroma to the plants.
temperature and high rate of transpiration.
(iii) Stinging hairs: They are hollow hairs that contain siliceous tips and enclose poison. They protect the plant from herbivores.
(iv) Glandular hairs: Most of the glandular trichomes produce essential oils. They provide aroma to the plants.
(II) Emergences : They are multicellular epidermal outgrowths which also contain some inner tissues prickles are an example of emergences. They are sharp and stiff outgrowth. They do not have vascular supply. They protect the plant from excessive transpiration, grazing animals and in some cases they help in climbing.

6.The lawn grass (Cynodon dactylon) needs to be mowed frequently to prevent its overgrowth. Which tissue is responsible for its rapid growth?
Soln. Lawn grass is a runner (stem . modification) of the Family Poaceae. It grows beautifully on the surface of the soil, thus covering entire soil surface, so it is grown for landscaping in gardens.
Meristematic tissues are responsible for rapid growth of these lawn grasses (Cynodon dactylon). The presence of apical bud in these grasses does not allow the nearby lateral buds to grow. This phenomenon is known 4s apical dominance. Therefore lawn grass needs to be moved frequently to prevent its overgrowth. When the apex of grass is cut frequently, it leads to the growth of lateral branches, that makes it more bushy.

7.Plants require waterfortheir survival. But when watered excessively, plants die. Discuss.
Soln. Plants require water in the process of synthesis of carbohydrates (photosynthesis) illustrated by the following equation :
6C02 + 12HzO C6H,206 + 6HzO+ 602 Hence, water is necessary for their survival. Plants die when watered in excess, because excess water replaces and removes the air trapped between the soil particles.
So, plant roots do not get 02 for respiration. Once, root cells die, water and mineral absorption is stopped and this leads to gradual death of the plant.

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?
Soln. Growth ring is laid down in a single season in a stem or root. It consists of two types of wood, spring wood and autumn wood. In spring, the activity of cambium is more and hence the wood elements are larger in size with wide lumen. It is called spring wood. The activity of cambium is less during winter or autumn and the wood elements are smaller in size with narrow lumen. It is called autumn wood. Spring wood and autumn wood of a year constitute annual ring or growth ring. The age of tree can be determined by counting annual rings in oldest or basal portion of tree trunk. Calculation of age of the tree by counting annual rings is called dendroch ¬ronology.

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.
Soln. Trunks of some of the aged tree species appear to be composed of several fused trunks. It is an example of anatomical abnormality due to anomalous secondary growth which occurs due to normal activity of an abnormally positioned cambium. Some
stems after secondary growth develop lobed outline and appear as formed by fusion of many stems, e.g., in Serjania, in the beginning a normal ring of vascular bundles is there, but after some time, some of adjacent bundles becoipe joined by cambium and they cut secondary xylem and secondary phloem in normal manner. At later stage, segments of cambium arise outside these fused vascular bundles and produce secondary xylem and secondary phloem.A periderm may be formed around each circle. Thus, a section of old stem shows concentric rings of xylem and phloem and vascular bundles are within.

10.What is the difference between lenticels and stomata?
Soln. Differences between lenticels and stomata are as follows:

11.Write the precise function of
(a) Sieve tube
(b) Interfascicular cambium
(c) Collenchyma
(d) Aerenchyma
Soln.(a) Sieve tubes are elongated tubular conducting channels of phloem which take part in translocation of organic food.
(b) Interfascicular cambium is a secondary meristem which takes part in formation of complete ring of vascular cambium by joining with intrafasicular cambial strips,
(c) Collenchyma is simple permanent tissue. It provides mechanical support to the growing parts of the plant such as young stem and petiole of a leaf. The cells of collenchyma assimilate food when they contain chloroplast.
(d) Aerenchyma is parenchymatous tissue storing air in its intercellular spaces. It helps hydrophytes in aeration and buoyancy.

12.The stomatal pore is guarded by two kidney shaped guard cells. Name the epidermal cells surrounding the guard cells. How does a guard cell differ from an epidermal cell? Use a diagram to illustrate your answer.
Soln. The epidermal cells surrounding the guard cells of stomata are called subsidiary cells.
Differences between guard cells and epidermal cells are as follows:
Following are labelled diagrams of stomata with bean-shaped and dumb-bell shaped guard cells, also showing the surrounding epidermal cells.

13.Point out the differences in the anatomy of, leaf of peepal (Ficus religiosa) and maize (Zea mays).. Draw the diagrams and label the differences.
Soln. Differences between Peepal (Dicot) and maize (Monocot) leaves are as follows :

14.Palm is a monocotyledonous plant, yet it increases in girth. Why and how?
Soln. Increase in diameter of the stem inpalm is accomplished by primary thickening meristem. This meristem originates below
the region of attachment of the young leaf primordia by periclinal divisions of the cells.In longitudinal section, it appears in the formof a flat or concave zone of several layersof rectangular cells oriented parallel to thesurface of the stem. At first the young stem , increases mainly in width by the activity of theprimary thickening meristem but in later stagesit is also responsible for the increase in height of the young stem. In some palms expansion of the ground tissue continues in the older part of the stem where parenchyma cells undergo division and cell expansion and the intercellular spaces, also increase in size. This type of growth is called diffused secondary growth.

Long Answer Type Questions
1.The arrangement of ovules within the ovary is known as placentation. What does the term placenta refer to? Draw various types of placentations in the flower as seen in T.S. and V.S.
Soln. Placenta is a parenchy-matous cushion present inside the ovary where ovules are borne. The arrangement of ovules within the ovary is known as placentation. It is of following types:
(i) Marginal : Here the gynoecium is monocarpellary and unilocular (one chambered). The placentae bearing the ovules in a row develop along the junction of the two margins of the folded carpels, inner to the ovary wall. This type of placentation is found in most of the members of the Family Leguminosae.
(ii) Parietal : Here the ovary is compound formed by the fusion of two or more carpels with their adjacent margins. Carpels are united to form only one chamber. Placentae are seen on the inner surface of the ovary, at the junctions of the carpels. Sometimes the unilocular ovary is found to be divided by the development of a false septum called as replum, e.g,. mustard, and other members of Cruciferae.
(iii) Axile : Here the gynoecium is poly- carpellary syncarpous. The ovary is many chambered and the number of chambers correspond to the number of carpels The walls of the carpels in the centre of the ovary are united to form an axis, which bears the placentae. Therefore, it is called as axile placentation e.g., Petunia (bilocular), Asphodelus (trilocular), China rose (pentalocular).
(iv) Free central : This is similar to axile placentation, except that the ovary is one , chambered. The partition walls are found in the early stage of the ovary forming chambers, which disintegrate later on, the ovary becomes unilocular. Only one swollen placenta bearing a number of ovules borne at the centre of the ovary, which is quite separate from the ovary wall, e.g., Dianthus, Primula.
(v) Basal – The ovary is unilocular and the placenta bearing a single ovule develop at the base of the ovary e.g., sunflower (Helianthus annuus).
(vi) Superficial : Here the gynoecium is
polycarpellary syncarpous and multilocular as in axile placentation. But here the placenta develop all round the inner surface of the partition walls and a large number of ovules are borne on the placenta without any specific order. Superficial placentation is found in both monocarpellary (e.g., Butomus) and syncarpous (e.g., Nymphaea) pistils.
2.Deciduous plants shed their leaves during hot summer or in autumn. This process of shedding of leaves is called abscission. Apart from physiological changes what anatomical mechanism is involved in the abscission of leaves.
Soln. Separation of leaves, bracts, flowers, floral parts and fruits from the plant without causing any injury is called abscission. Abscission layer is made up of two layers of cambium like cells. Cells of these layers are smaller and contain more of protoplasm and starch. Tyloses develop in the xylem of vascular tissue. In cambium like cells of abscission layer, the middle lamella swells up anpl becomes mucilaginous. Later on in response to any of several environmental changes (such as lowering temperatures, decreasing day lengths or light intensities, lack of adequate water and poor availability of nutrients from the soil, etc.) the pectins in the middle lamella of the cells of abscission are broken down by enzymes due to which the cell separate apart. The leaf is now attached to the stem only with the help of vascular tissue, which separates from the stem by wind and rain and leaf falls down from the plant.

3. Is Pinus an evergreen tree? Comment.
Soln. Evergreen plants are those which have leaves persistent in all the four seasons. In contrast to deciduous plants which completely lose their foliage during winter or dry season. Pinus which belongs to gymnosperms is an evergreen tree. The flowering plants under conditions of extreme cold shed their leaves and become dormant. But, Pinus is well adapted to such conditions such as leaves of Pinus have thick cuticle, sunken stomata and needle like shape which helps in conserving water and reduce transpiration in dry conditions associated with cold habitat.So, it continues to manufacture food during this period and grow. This shows that Pinus is an evergreen tree. It does not shed its leaves, (i.e., needles) under any condition.

4. Assume that a pencil box held in your hand, represents a plant cell. In how many possible planes can it be cut? Indicate these cuts with the help of line drawings.
Soln. (A) If a pencil box (plant cell) is cut in different planes it will result in radial symmetry.
(B) If a pencil box (plant cell) is cut in two equal halves it w’ill result in bilateral symmetry.

5.Each of the following terms has some anatomical significance. What do these terms mean? Explain with the help of line diagrams.
(a) Plasmadesmoses/ Plasmodesmata
(b) Middle lamella
(c) Secondary wall
Soln. (a) Plasmodesmata: Plasmodesmata are cytoplasmic bridges between adjacent plant cells which develop in the minute pores of their walls. They form a protoplasmic continuum called symplast. Plasmodesmata is lined by plasma membrane and encloses tubular extension of endoplasmic reticulum called desmotubules. The space between desmotubules and plasma membrane contains 8-10 microchannels. Plasmodesmata form channels for controlled passage of small sized particles between adjacent cells as well as transfer of some specific signals.
(b) Middle lamella: Middle lamella is a thin, amorphous and cementing layer between two adjacent cells. It is first layer which is deposited at the time of cytokinesis. It is made up of pectates of calcium and. magnesium. Middle lamella is absent on the outer side of surface cells. The ripened fruits become softened due to partial dissolution of pectic compounds of middle lamella.
(c) Secondary cell wall: Secondary cell wall is produced in some mature cells when the latter have stopped growth, e.g., tracheids, vessel elements, fibres, collenchyma. Secondary wall is laid inner to the primary wall by deposition of materials over the surface of secondary structures. It is 3-10 pm thick and made up of at least three layers and sometimes more. They are named S1( S2, S3, Sx, etc. The composition of secondary wall is basically similar to the primary wall in having cellulose microfibrils embedded in a matrix of pectin and hemicellulose. Cellulose content is usually high in secondary cell wall in comparison to primary cell wall while hemicellulose content is comparatively low (upto 25%) rather than primary cell wall (upto 50%).
A number of different materials can be deposited in secondary cell wall matrix are lignin, suberin, cutin, silica, minerals, waxes, tannins, resins, etc.

6.Distinguish between the following:
(a) Exarch and endarch condition of protoxylem
(b) Stele and vascular bundle
(c) Protoxylem and metaxylem
(d) Interfasicular cambium and intrafasicular cambium
(e) Open and closed vascular bundles
(f) Stem hair and root hair
Soln.(a) Differences between exarch and endarch xylem are as follows:
(b) Differences between stele and vascular bundle are as follows:
(c) Differences between protoxylem and metaxylem are as follows:
(d) Differences between intrafascicular cambium and interfascicular cambium are as follows:
(e) Differences between open and closed vascular bundles are as follows:
(f) Differences between stem hair and root hair are as follows: