Chapter 5: Morphology of Flowering Plants

Class 11 Biology Chapter 5 Morphology of Flowering Plants Exercise Questions and Answers :

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

Answer :

Pinnately Compound Leaf	Palmately Compound Leaf
Leaflets are arranged along a central axis, like the structure of a feather.	Leaflets are attached to a single point at the end of the petiole, resembling the fingers of a hand or palm.
Leaflets are attached to the central axis (rachis) in a feather-like pattern along its sides.	Leaflets are attached at the tip of the petiole (like fingers extending from a palm), radiating outward from a single point.
Examples include leaves of roses and acacia trees.	Examples include leaves of the horse chestnut and poison ivy plants.
Leaflets may be elongated or lance-shaped.	Leaflets can have various shapes, often resembling the lobes of a palmately divided hand.
Leaflets typically have a pinnate vein pattern, with secondary veins running parallel to the midrib.	Leaflets can have a radial or palmate vein pattern, with veins radiating from a central point.

2. Explain with suitable examples the different types of phyllotaxy.

Answer :  Phyllotaxy, the arrangement of leaves on a stem or branch, can be categorized into three main types: alternate, opposite, and whorled .

Alternate Phyllotaxy:

(i) In the alternate phyllotaxy, a single leaf arises at each node in an alternate manner along the stem or branch.

(ii) This pattern allows each leaf to have access to adequate sunlight and reduces shading of lower leaves.

Examples: China rose (Hibiscus rosa-sinensis), mustard (Brassica), and sunflower (Helianthus annuus).

Opposite Phyllotaxy:

(i) In the opposite phyllotaxy, a pair of leaves arises at each node and lies opposite to each other, forming a symmetrical pattern along the stem or branch.

(ii) Leaves in an opposite arrangement are typically at right angles to the pair above and below.

Examples: Calotropis (Calotropis procera) and guava (Psidium guajava) plants.

Whorled Phyllotaxy:

(i) In the whorled phyllotaxy, more than two leaves arise at a node and form a whorl or circle around the stem or branch.

(ii) Leaves in a whorl arrangement are evenly spaced around the stem, often in a circular or spiral pattern.

Examples: Alstonia (Alstonia scholaris) and some species of Oleander (Nerium) have whorled phyllotaxy.

3. Define the following terms:

(a) aestivation (b) placentation (c) actinomorphic

(d) zygomorphic (e) superior ovary (f) perigynous flower

(g) epipetalous stamen

Answer :  (a) Aestivation : Aestivation refers to the arrangement of sepals or petals in a floral bud concerning other members of the same whorl. It plays a crucial role in protecting floral components and facilitating their efficient development as the bud opens.

(b) Placentation :  Placentation is the arrangement of ovules within the ovary of a flower. The different types of placentation optimize seed development and fertilization by organizing ovules in various patterns within the ovary.

(c) Actinomorphic : Actinomorphic flowers have radial symmetry, where their floral parts are arranged symmetrically around a central point. They can be divided into similar halves in multiple ways. Examples include lilies and daisies.

(d) Zygomorphic : Zygomorphic flowers exhibit bilateral symmetry, meaning they can be divided into two equal halves only along one plane. One half is a mirror image of the other. Orchids and snapdragons are examples of zygomorphic flowers.

(e) Superior Ovary : A flower with a superior ovary has its ovary positioned above the attachment point of other floral parts, such as sepals, petals, and stamens. This is a characteristic feature in many flowers like roses and apples.

(f) Perigynous Flower : A perigynous flower has its floral parts, such as sepals, petals, and stamens, attached around the rim of the ovary, creating a shallow cup-like structure. An example is the cherry blossom.

(g) Epipetalous Stamen : Epipetalous stamens are stamens that are attached to or fused with the petals of a flower. They are typically found in flowers where the stamens are connected to the petal tube or base, forming a ring around the petals, as seen in the mallow family (Malvaceae).

4. Differentiate between

(a) Racemose and cymose inflorescence

(b) Apocarpous and syncarpous ovary .

Answer : (a) Racemose and Cymose Inflorescence :

Racemose Inflorescence	Cymose Inflorescence
Indeterminate growth, with the main axis continuing to grow and produce flowers along its length.	Determinate growth, where the main axis terminates in a flower and lateral branches develop to produce more flowers.
Flowers are arranged along a single central axis.	Flowers are arranged along multiple lateral branches.
Examples include the raceme in mustard plants and the spike in wheat.	Examples include the cyme in forget-me-not and the umbel in parsley.
The main axis can continue growing, producing flowers in an acropetal (older to younger) order.	Growth is limited as the main axis terminates with a flower, and lateral branches may grow further.
Raceme, spike, panicle, and catkin are some common types.	Cyme, umbel, and compound cyme are typical examples.

(b) Apocarpous and Syncarpous Ovary:

Apocarpous Ovary	Syncarpous Ovary
Apocarpous ovaries consist of multiple, separate carpels (ovule-bearing structures).	Syncarpous ovaries are composed of fused carpels, forming a single structure.
Multiple styles or stigma lobes, corresponding to the number of separate carpels.	Single style or stigma, often shared by the fused carpels.
Examples include the buttercup and rose families, where each pistil has its own separate ovary.	Examples include the pea and lily families, where the ovary is formed from fused carpels.
Fertilization occurs within individual carpels, allowing for potential variation in seed development.	Fertilization typically occurs within a single, fused ovary, leading to uniform seed development.
Apocarpous ovaries can lead to multiple fruits, each developing from a separate carpel.	Syncarpous ovaries typically result in a single fruit or a fruit with multiple compartments.

5. Draw the labelled diagram of the following:

(i) gram seed (ii) V.S. of maize seed

Answer : (i) gram seed

(ii) V.S. of maize seed

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

Answer : Solanum nigrum (Makoi) Flower Description :

Inflorescence: The flowers of Solanum nigrum are usually solitary, meaning they are borne individually rather than in clusters.

Calyx (Sepals): The calyx consists of five green sepals that are fused at their base. These sepals are typically lance-shaped and have pointed tips.

Corolla (Petals): The corolla is made up of five small, white to pale yellow, narrowly ovate petals. The petals are usually deeply divided, giving the appearance of ten petals, but they are in fact five, often with a star-like appearance.

Androecium (Stamens): Solanum nigrum flowers have five stamens, which are the male reproductive structures. The filaments are slender and bear anthers at their tips, which contain pollen.

Gynoecium (Pistil): The pistil, the female reproductive structure, consists of a single, superior ovary, which matures into a berry-like fruit. The style is long and slender, with a stigma at the tip, ready for pollination.

Flower Symmetry: These flowers exhibit radial symmetry, meaning they can be divided into equal parts along multiple axes.

Size: The size of a Solanum nigrum flower is relatively small, typically around 1 to 1.5 centimeters in diameter.

Fragrance: Solanum nigrum flowers are often not strongly scented, and their fragrance, if present, is typically mild.

Bloom Time: These flowers bloom during the growing season, usually in the warmer months.

Pollination: Solanum nigrum flowers are primarily pollinated by insects, such as bees, which transfer pollen from the stamens to the stigma, facilitating fertilization and fruit development.

Additional Notes: Solanum nigrum, or "makoi," is a common weed and a minor edible plant in some regions. It is known for its distinctive white to pale yellow flowers and dark berries that follow, which are used in traditional medicine and occasionally as food. The flowers and berries can vary in color slightly depending on the plant's variety and environmental conditions

7. Describe the various types of placentations found in flowering plants.

Answer : The arrangement of ovules within the ovary is known as placentation. The placentation are of different types

Marginal Placentation : In this type, a single elongated placenta is attached to one side of the ovary. Ovules are found along the ventral suture (the line where the two carpels join) in a single row.

Axile Placentation : In axile placentation, there are multiple placentas or locules within the ovary, and they are located in the center of the ovary. Ovules are attached to the central axis, with partitions dividing the ovary into separate chambers or locules. This type is commonly found in plants with a compound ovary, like the tomato.

Free Central Placentation : In this type, a single, elongated central placenta occurs in the ovary, with ovules attached along the length of the placenta. This arrangement can be found in members of the Malvaceae family, like hibiscus.

Parietal Placentation : In parietal placentation, ovules are attached to the inner wall of the ovary. The ovules are found on the walls of the ovary, and this arrangement is common in many dicot plants.

Basal Placentation : Basal placentation occurs when the placenta is at the base of the ovary, and a single ovule is attached to it. This is characteristic of some monocot flowers like lilies.

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

Answer :  A flower is the reproductive structure found in angiosperms (flowering plants) that serves as the site for sexual reproduction. It consists of four main floral whorls, each with specific parts and functions:

  

Calyx (Sepals): The calyx is the outermost whorl of the flower, composed of sepals. Sepals are usually green, leaf-like structures that enclose and protect the inner floral parts when the flower is in bud form. They can also vary in size and shape, depending on the plant species.

                

Corolla (Petals): The corolla is the second whorl and consists of petals. Petals are often brightly colored and serve to attract pollinators like insects and birds with their coloration and sometimes fragrance. The corolla can exhibit a wide range of shapes and sizes.

             

Androecium (Stamens): The androecium is the third whorl and is the male reproductive part of the flower. It is made up of stamens, which consist of two main parts: the filament and the anther. The filament is a slender stalk that holds the anther, which produces pollen, containing the male gametes.

               

Gynoecium (Carpels or Pistils): The gynoecium is the innermost whorl and represents the female reproductive part of the flower.

                          

It is composed of one or more carpels (also called pistils), each of which consists of three main parts:

Ovary: The ovary is the swollen base of the carpel, and it houses one or more ovules. After pollination and fertilization, the ovary develops into a fruit, and the ovules become seeds.

Style: The style is a slender tube-like structure that connects the ovary to the stigma.

Stigma: The stigma is the sticky or receptive surface at the top of the style, where pollen grains land during pollination.

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

Answer : Inflorescence is the arrangement of flowers on the floral axis of a plant. This occurs when the shoot apical meristem changes into a floral meristem, causing the internodes not to elongate and the stem axis to become condensed. Instead of producing leaves, the apex of the shoot tip produces various types of floral appendages laterally at successive nodes. When a shoot tip transforms into a flower, it always forms a solitary flower, and the way these flowers are organized and positioned along the floral axis is what we refer to as the inflorescence.

The two main types of inflorescence are:

(i) Racemose : In racemose type of inflorescences the main axis continues to grow, the flowers are borne laterally in an acropetal succession .

                 

                Racemose inflorescence

(ii) Cymose : In cymose type of inflorescence the main axis terminates in a flower, hence is limited in growth. The flowers are borne in a basipetal order .

          

               Cymose inflorescence

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

Answer : The arrangement of floral members in relation to their insertion on the thalamus are three types :

Hypogynous: In a hypogynous flower, the floral members (sepals, petals, and stamens) are attached below the ovary on the thalamus. The ovary is superior in this arrangement, sitting above the attachment point of other floral parts. An example of a hypogynous flower is the rose.

Perigynous: In perigynous flowers, the floral members are attached at the same level, surrounding the ovary, which is typically partially sunken into the thalamus. This results in the ovary being partially inferior and partially superior. An example of a perigynous flower is the apple.

Epigynous: Epigynous flowers have their floral members attached above the ovary on the thalamus. The ovary is considered inferior in this case, as it is situated beneath the attachment point of the other floral parts. An example of an epigynous flower is the strawberry.