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NCERT Solutions · Class 11 Biology Morphology of Flowering Plants

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Exercises 5.1–5.10

  1. Exercise 5.1

    How is a pinnately compound leaf different from a palmately compound leaf?

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    The difference lies in where the leaflets are attached: along a common axis in a pinnately compound leaf, at a single point in a palmately compound leaf.
    Pinnately compound leaf: a number of leaflets are present on a common axis, the rachis, which represents the midrib of the leaf, e.g., neem.
    Palmately compound leaf: the leaflets are attached at a common point, i.e., at the tip of the petiole, e.g., silk cotton.
    Both are compound (not simple) because the incisions of the lamina reach up to the midrib, breaking it into a number of leaflets.
    In both, a bud is present in the axil of the petiole, but never in the axil of a leaflet.
    NCERT_Solution_Class11_Biology_Ch5_Q5-1

  2. Exercise 5.2

    Explain with suitable examples the different types of phyllotaxy.

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    Phyllotaxy is the pattern of arrangement of leaves on the stem or branch. It is usually of three types.
    Alternate: a single leaf arises at each node in an alternate manner, as in china rose, mustard and sunflower.
    Opposite: a pair of leaves arise at each node and lie opposite to each other, as in Calotropis and guava.
    Whorled: more than two leaves arise at a node and form a whorl, as in Alstonia.
    NCERT_Solution_Class11_Biology_Ch5_Q5-2

  3. Exercise 5.3

    Define the following terms:
    (a)
    aestivation
    (b)
    placentation
    (c)
    actinomorphic
    (d)
    zygomorphic
    (e)
    superior ovary
    (f)
    perigynous flower
    (g)
    epipetalous stamen

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    (a)
    Aestivation - the mode of arrangement of sepals or petals in the floral bud with respect to the other members of the same whorl (valvate, twisted, imbricate, vexillary).
    (b)
    Placentation - the arrangement of ovules within the ovary (marginal, axile, parietal, basal, central and free central).
    (c)
    Actinomorphic - a flower that can be divided into two equal radial halves in any radial plane passing through the centre, i.e., radially symmetrical, e.g., mustard, datura, chilli.
    (d)
    Zygomorphic - a flower that can be divided into two similar halves only in one particular vertical plane, i.e., bilaterally symmetrical, e.g., pea, gulmohur, bean, Cassia.
    (e)
    Superior ovary - the ovary of a hypogynous flower, in which the gynoecium occupies the highest position on the thalamus and all the other floral parts are situated below it, e.g., mustard, china rose, brinjal.
    (f)
    Perigynous flower - a flower in which the gynoecium is situated in the centre and the other parts are located on the rim of the thalamus almost at the same level; the ovary here is said to be half inferior, e.g., plum, rose, peach.
    (g)
    Epipetalous stamen - a stamen that is attached to the petals, as in brinjal. (When attached to the perianth instead, as in lily, it is epiphyllous.)

  4. Exercise 5.4

    Differentiate between
    (a)
    Racemose and cymose inflorescence
    (b)
    Apocarpous and syncarpous ovary

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    (a)
    Racemose and cymose inflorescence
    Racemose: the main axis continues to grow and does not terminate in a flower.
    Flowers are borne laterally in an acropetal succession (older flowers below, younger towards the tip).
    Cymose: the main axis terminates in a flower, hence it is limited in growth.
    Flowers are borne in a basipetal order (older flower at the tip, younger below it).
    (b)
    Apocarpous and syncarpous ovary
    Apocarpous: more than one carpel is present and the carpels remain free, as in lotus and rose.
    Syncarpous: the carpels are fused together, as in mustard and tomato.

  5. Exercise 5.5

    Draw the labelled diagram of the following:
    (i)
    gram seed
    (ii)
    V.S. of maize seed

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    Both diagrams are printed in the chapter - the gram seed is the dicotyledonous seed of Figure $\displaystyle 5.14$ and the V.S. of maize seed is Figure 5.15.(i) Gram seed (dicotyledonous, non-endospermous)
    Draw the seed in outline and show it split open along one face, with one cotyledon removed so that the embryo lies exposed.
    Outermost, draw the seed coat as a boundary line; label its outer layer testa and inner layer tegmen.
    On the concave edge of the seed coat, mark a scar - the hilum - through which the developing seed was attached to the fruit.
    Just above the hilum, mark a small pore - the micropyle.
    Inside, draw one large fleshy cotyledon filling most of the seed (the second one lies behind it); it is full of reserve food, as gram has no endosperm in the mature seed.
    Between the cotyledons draw the short embryonal axis, and label its two ends: the radicle at the end pointing towards the micropyle and the plumule at the other end.
    Labels required: seed coat (testa, tegmen), hilum, micropyle, cotyledon, plumule, radicle.
    (ii) V.S. of maize seed (monocotyledonous, endospermous)
    Draw the grain as an elongated oval cut lengthwise.
    Outline it with a thin membranous layer labelled seed coat fused with the fruit wall - in maize the seed coat is membranous and generally fused with the fruit wall.
    Fill the bulk of the interior with the endosperm, the food-storing tissue.
    Along the outer edge of the endosperm draw a single narrow layer of cells labelled aleurone layer - the proteinous layer that separates the endosperm from the embryo.
    At one end, in a groove of the endosperm, draw the small embryo.
    Within the embryo draw the one large, shield-shaped cotyledon, the scutellum, lying flat against the endosperm.
    From the scutellum draw the short axis: label the plumule at its upper end, enclosed in a sheath called the coleoptile, and the radicle at its lower end, enclosed in a sheath called the coleorhiza.
    Labels required: seed coat and fruit wall, aleurone layer, endosperm, scutellum, coleoptile, plumule, radicle, coleorhiza, embryo.
    NCERT_Solution_Class11_Biology_Ch5_Q5-5

  6. Exercise 5.6

    Take one flower of the family Solanaceae and write its semi-technical description. Also draw their floral diagram.

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    Flower taken: Solanum nigrum (makoi), family Solanaceae - the 'potato family'.Semi-technical description
    Habit: a herb (the family has mostly herbs and shrubs, rarely small trees).
    Stem: herbaceous, rarely woody; aerial, erect, cylindrical, branched, solid or hollow, hairy or glabrous (underground in potato, Solanum tuberosum).
    Leaves: alternate, simple, rarely pinnately compound, exstipulate; venation reticulate.
    Inflorescence: solitary and axillary, or cymose as in Solanum.
    Flower: bisexual, actinomorphic.
    Calyx: sepals five, united (gamosepalous), persistent; aestivation valvate.
    Corolla: petals five, united (gamopetalous); aestivation valvate.
    Androecium: stamens five, epipetalous.
    Gynoecium: bicarpellary, obliquely placed, syncarpous; ovary superior, bilocular, placenta swollen with many ovules; placentation axile.
    Fruit: a berry or a capsule.
    Seeds: many, endospermous.
    Floral formula: \(\displaystyle \oplus\; K_{(5)}\; C_{(5)}\; A_{5}\; \underline{G}_{(2)} \), with the bisexual symbol placed before \(\displaystyle \oplus \); the brackets show fusion within a whorl, and a line drawn above C and A shows the adhesion of the epipetalous stamens to the corolla.
    Floral diagram - what to draw
    Put a dot at the top to show the position of the mother axis with respect to the flower.
    Draw the whorls as concentric circles, calyx outermost and gynoecium in the centre.
    Calyx: five sepals in the outermost circle, drawn touching one another (united, valvate).
    Corolla: five united petals in the next circle, inside the calyx.
    Androecium: five anthers in the next circle, each alternating with the petals - drawn between two petals, not opposite one - and joined to the corolla circle by a short line to show that the stamens are epipetalous.
    Gynoecium: in the centre, a bicarpellary syncarpous ovary drawn obliquely (tilted to the mother axis), shown in section as two chambers with a swollen central placenta bearing many ovules - i.e., axile placentation.
    NCERT_Solution_Class11_Biology_Ch5_Q5-6

  7. Exercise 5.7

    Describe the various types of placentations found in flowering plants.

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    Placentation is the arrangement of ovules within the ovary; the chapter names marginal, axile, parietal, basal, central and free central types.
    Marginal: the placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge in two rows, as in pea.
    Axile: the placenta is axial and the ovules are attached to it in a multilocular ovary, as in china rose, tomato and lemon.
    Parietal: the ovules develop on the inner wall of the ovary or on its peripheral part; the ovary is one-chambered but becomes two-chambered due to the formation of a false septum, e.g., mustard and Argemone.
    Free central: the ovules are borne on a central axis and septa are absent, as in Dianthus and Primrose.
    Basal: the placenta develops at the base of the ovary and a single ovule is attached to it, as in sunflower and marigold.
    Note: 'central' is listed among the types in the chapter but is not described or illustrated separately there.
    NCERT_Solution_Class11_Biology_Ch5_Q5-7

  8. Exercise 5.8

    What is a flower? Describe the parts of a typical angiosperm flower.

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    What a flower is
    The flower is the reproductive unit in the angiosperms, meant for sexual reproduction.
    It is a modified shoot: the shoot apical meristem changes to a floral meristem, the internodes do not elongate, the axis gets condensed, and the apex produces floral appendages laterally at successive nodes instead of leaves.
    Parts of a typical angiosperm flower
    A typical flower has four whorls borne successively on the swollen end of the stalk or pedicel, called the thalamus or receptacle: calyx, corolla, androecium and gynoecium.
    Calyx and corolla are the accessory organs; androecium and gynoecium are the reproductive organs.
    Calyx: the outermost whorl; its members are sepals, generally green and leaf-like, and they protect the flower in the bud stage. It may be gamosepalous (united) or polysepalous (free).
    Corolla: composed of petals, usually brightly coloured to attract insects for pollination. It may be gamopetalous or polypetalous, and tubular, bell-shaped, funnel-shaped or wheel-shaped.
    Androecium: composed of stamens, the male reproductive organs. Each stamen has a stalk or filament and an anther; each anther is usually bilobed with two pollen-sacs per lobe, in which pollen grains are produced. A sterile stamen is a staminode.
    Gynoecium: the female part, made of one or more carpels. A carpel has three parts - the stigma (receptive surface for pollen, at the tip), the style (the elongated tube connecting stigma to ovary) and the ovary (the enlarged basal part). Each ovary bears one or more ovules on a cushion-like placenta.
    Carpels may be free (apocarpous, as in lotus and rose) or fused (syncarpous, as in mustard and tomato).
    After fertilisation the ovules develop into seeds and the ovary matures into a fruit.
    In some flowers, like lily, the calyx and corolla are not distinct and are together termed the perianth.
    A flower with both androecium and gynoecium is bisexual; one with only stamens or only carpels is unisexual.
    NCERT_Solution_Class11_Biology_Ch5_Q5-8

  9. Exercise 5.9

    Define the term inflorescence. Explain the basis for the different types inflorescence in flowering plants.

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    Inflorescence is the arrangement of flowers on the floral axis.
    The basis of the two major types is whether the apex of the main axis gets developed into a flower or continues to grow.
    Racemose: the main axis continues to grow, so the flowers are borne laterally in an acropetal succession - the older flowers lie at the base and the younger ones towards the tip.
    Cymose: the main axis terminates in a flower and is therefore limited in growth, so the flowers are borne in a basipetal order - the oldest flower is at the tip and the younger ones below it.
    Related point from the chapter: when a shoot tip itself transforms into a flower, the flower is always solitary.
    NCERT_Solution_Class11_Biology_Ch5_Q5-9

  10. Exercise 5.10

    Describe the arrangement of floral members in relation to their insertion on thalamus.

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    Floral members are arranged in three ways on the thalamus, depending on the position of the calyx, corolla and androecium with respect to the ovary: hypogynous, perigynous and epigynous.
    Hypogynous: the gynoecium occupies the highest position on the thalamus and all the other parts are situated below it; the ovary is said to be superior, e.g., mustard, china rose, brinjal.
    Perigynous: the gynoecium is situated in the centre and the other parts are located on the rim of the thalamus, almost at the same level as the gynoecium; the ovary is said to be half inferior, e.g., plum, rose, peach.
    Epigynous: the margin of the thalamus grows upward, enclosing the ovary completely and fusing with it, so the other floral parts arise above the ovary; the ovary is said to be inferior, e.g., guava, cucumber and the ray florets of sunflower.
    NCERT_Solution_Class11_Biology_Ch5_Q5-10