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Semi Technical Description of a Flowering Plant – Class 11 Biology

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  • Last Updated : 29 Sep, 2022
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Morphology refers to the study of forms or external features of an organism. While studying the morphology of an organism we focus on its external appearance and on parts that are easily visible to the naked eye. Fruits, leaves, flowers, stems, and roots are the important part of a flowering plant which is included under the morphology of a plant. The plant body has two main systems the Root system and the Shoot system. The underground part of a flowering plant is called the root system. The portion above forms the shoot system. Approx. 3,00,000 species are included in the category of flowering plants. Wide diversity can be seen in this category. It is observed and believed by the ancestors that the first flowering plant was seen 140 million years ago. The most important part of the flowering plant is the flower which is also the reproductive part of the flower. When pollen from the male flower goes to the stamen of the female flower then fertilization will take place leading to the formation of seed.

Root

Roots are that part of the plant which is responsible for providing the proper amount of nutrients to the whole plant body by absorbing from the soil. Another main track which is done by roots is aerating which helps in the proper growth and development of the plant. The roots grow into the soil and bear Primary, Secondary and Tertiary roots, and Root Hairs.

Types of the Root System

  • Taproot: It is a straight tapering root growing vertically downwards and forming the center from which subsidiary rootlets spring. Generally, dicots possess tap roots. Eg: Mustard.
  • Fibrous roots: These are roots that have no prominent central axis and branches in all directions. Monocots possess these types of roots. Eg: Wheat.
  • Adventitious root: When roots arise from parts other than the radicle, the roots are called adventitious roots. Eg: Monstera, Banyan, Grasses.

Regions of Root

  • Root cap: It is a thimble-like structure that protects the root tips.
  • Region of meristematic activity: The cells of this region are small, thin-walled, and with dense protoplasm.
  • Region of elongation: The enlargement of these cells leads to an increase in the length of the root.
  • Region of maturation: The cells of elongation mature and differentiate and form these cells.
  • Root hair: The epidermal cells possess fine, delicate, thread-like structures called root hairs.

Modifications of Roots

  • Storage roots: These roots are modified to store food. Eg: Carrot, Turnip, adventitious roots of Sweet Potato, and Asparagus.
  • Prop roots: These hanging structures are meant for providing support to the plant. Eg: Banyan.
  • Stilt roots: These are supporting roots coming out of the lower nodes of the stem. Eg: Maize, Sugarcane.
  • Pneumatophores: These roots grow in swampy areas and come out of the soil vertically upwards to aid in the respiration process. Eg: Rhizophora.

Stem

Stem

Stem

The main structure of vascular plants besides roots is the stem. Supply of dissolved substances to flowers, fruits, and leaves from roots is done by stems only. The area from one node to another is known as the internode. Stems help in giving support and in the growth of leaves, fruits, and flowers. The stem bears organs like Leaves, Flowers, Fruits, Branches, Nodes, Internodes, etc.

Modifications of Stem

  • Storage stems: These stems are modified for food storage. Eg: Potato, Ginger, Turmeric, Zaminkand, Colocasia.
  • Stem tendrils: These are modified axillary buds which help plants in climbing. Eg: Cucumber, Pumpkins, Watermelon, and Grapevines.
  • Thorns: Axillary buds of the stem get modified into woody, straight and pointed thorns. Eg: Bougainvillea, Citrus.
  • Phylloclade: It is a flattened branch or stem-joint resembling and functioning as a leaf. Eg: Opuntia, Euphorbia.
  • Underground stems are present in Grass and strawberries.
  • Sub-aerial stems are present in Mint and Jasmine.
  • Aquatic roots are found in Pistia and Eichhornia.
  • Sub-aerial lateral branches are found in Banana, Pineapple, and Chrysanthemum.

Leaf

Principle appendage of any vascular plant or leaves. Collectively leaves are known as foliage. The color of leaves is dependent on the presence of the pigment in them if they have a green pigment called chlorophyll then the leaves will be of green color if another pigment is present then it will give color to the leaves accordingly. It is a lateral, flattened structure arising from the axial or below the node.

Parts of Leaf

  • Leaf base
  • Stipules
  • Petiole
  • Lamina/Leaf Blade
  • Veins/Veinlets/Midrib
  • Axillary buds

Venation

  • Reticulate Venation: Here the veins and veinlets are unevenly dispersed throughout the whole lamina producing a network. Found in dicots.
  • Parallel Venation: It is a vein configuration in which the veins run parallel to one another. It is mostly found in monocot leaves.

Types of Leaves

  • Simple Leaf: Here the lamina is entire or when incised, the incisions don’t reach the midrib. 
  • Compound Leaf: Here the incisions reach the midrib dividing the leaf into many small leaflets. These are further two types:
    • Pinnately compound: Here a number of leaflets are present on a common axis called the rachis. Eg: Neem.
    • Palmately compound: Here the leaflets are attached at a common point. Eg: Silk cotton.

Phyllotaxy

Most of the distinctive classes of patterns in nature are made due to phyllotactic spirals. There is a variety of different patterns in which the leaves are arranged in different plants which give them a unique appearance. It is the pattern of arrangement of leaves on the stem or branch. Its types are:

  • Alternate: Here a single leaf arises at each node in an alternate manner. Eg: China rose, Mustard, Sunflower.
  • Opposite: Here a pair of leaves arise at each node. Eg: Calotropis, Guava.
  • Whorled: Here more than two leaves arise at a node. Eg: Alstonia.

Modifications of Leaves

  • Tendrils: They help in climbing. Eg: Peas.
  • Spines: They help in defense. Eg: Spines of Cacti.
  • Storage leaves: Fleshy leaves of Onion and Garlic store food.
  • Phyllode: In xeric plants like Australian acacia, the petioles become green and synthesize food. 
  • Leaves of insectivorous plants like Pitcher plant and Venus-fly trap are modified leaves. 

Flower

Flower

 

Bloom or blossom are the other names that are given to flowers. The main function of a flower is maintaining the genetic line by reproduction. No reproduction can be either asexual or sexual means the pollination can be self or it can be cross-pollination. In the case of self-pollination, both anther and stamen are present on the same flower, and in the case of cross-pollination, the anther and stamen are present on different flowers. The flower is the reproductive structure of a plant. It has a beautiful appearance and an attractive odor. It has four main whorls:

  • Calyx (sepals)
  • Corolla (petals)
  • Gynoecium (pistils/carpels)
  • Androecium (stamens)

Calyx and Corolla constitute the nonessential whorls whereas Gynoecium and Androecium form the essential whorls. Calyx or basically the sepals are green tiny leaf-like structures that protect the flower in the bud stage. Corolla or the petals are large, attractive, colorful, and have a pleasant odor. They are meant for attracting insects and animals for pollination purposes. Gynoecium or pistil is the female reproductive whorl of the flower. It has three parts. The broad stigma serves as a landing platform for the pollen grains, the style which is a fine tube aiding in the transfer of pollens to the ovary and an ovary which is the female reproductive organ of the flower and produces the female gamete known as the egg. The Androecium or stamen constitutes the male reproductive whorl of the flower and has two parts. The pollen-producing anther is at the tip of a thin thread-like filament. Having learned the parts of flowers, let’s now learn how flowers are arranged on the plant.

Inflorescence

Inflorescence refers to the arrangement of flowers on the plant. At the axis of a plant, flowers are formed which are a modified part of the seed plant. Variations in proportions, compressions, phyllotaxis, and internode are all can be included in the modification of plants. The two main types of inflorescence are as follows:

  • Racemose Inflorescence: Here the flowers are arranged in an acropetal succession which means that new flowers are added on the top and the old flowers are found at the bottom. The main axis continues to grow as there is no flower at its tip.
  • Cymose inflorescence: Here the flowers are arranged in a basipetal succession which means that old flowers are present above the new flowers. New flowers are added in the downward direction. The main axis terminates into a flower and hence does not freely grow.

Aestivation

In plants it happens in summer, more or less it is similar to hibernation and animal dormancy where there is inactivity in plants and the metabolic rate is also decreased. The mode of arrangement of sepals and petals in a flower with respect to the other members of the same whorl is known as aestivation.

  • Valvate: Here the sepals/petals just touch one another at the margin without overlapping. Eg: Calotropis.
  • Twisted: Here one margin of the appendage overlaps the other. Eg: China rose, Cotton, Lady’s finger.
  • Imbricate: Here the margins of sepals/petals overlap one another but not in any particular direction as in Cassia, Gulmohar.
  • Vexillary: Here the largest petal, the standard overlaps the two lateral petals called the wings which in turn overlaps the two smallest anterior petals called the keel. Eg: Pea, Bean.

Placentation

The arrangement of the ovules within the ovary is called placentation. The nutrients from maternal tissue are provided to the developing embryo by the placenta. It also removes waste from the embryo just like the function of the placenta in humans.  Its types are as follows:

  • Marginal: Here the placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows. Eg: Pea. 
  • Axile: Here the placenta is axial and the ovules are attached to it in a multilocular ovary. Eg: Lemon, Tomato, China rose.
  • Parietal: Here the ovules develop on the inner wall of the ovary or on the peripheral part. Eg Mustard, Argemone.
  • Free central: Here the ovules are borne on the central axis and septa are absent. Eg: Primrose, Dianthus.
  • Basal: Here the placenta develops at the base of the ovary and a single ovule is attached to it. Eg: Marigold, Sunflower.

Important Terminologies

Parts of flowers

  • Perianth: When the calyx and corolla are not separate whorls, this single whorl is called perianth. Eg: lily.
  • Unisexual: It is the flower-bearing only one type of sex organ either male or female.
  • Bisexual: It bears both male and female flowers.
  • Actinomorphic: These are flowers possessing radial symmetry. A flower cut through any plane divides into two equal halves. Eg: Mustard, Datura, Chili.
  • Zygomorphic: This type possesses bilateral symmetry. These flowers have two planes of symmetry. Eg: Gulmohar, Pea, Bean, Cassia.
  • Asymmetric: This type of flower doesn’t possess any axis of symmetry. Eg: Canna.
  • Trimerous: These are flowers bearing floral appendages in multiples of three.
  • Tetramerous: These are flowers bearing floral appendages in multiples of four.
  • Pentamerous: These are flowers bearing floral appendages in multiples of five.
  • Bracteate: These flowers bear small reduced leaves called bracts at their base.
  • Ebracteate: These flowers don’t bear bracts.
  • Hypogynous: These flowers have a superior ovary i.e. gynoecium above all other floral whorls. Eg: China rose, Mustard, Brinjal.
  • Perigynous: These flowers have a half-inferior ovary i.e. gynoecium lies in the same line as the other floral whorls. Eg: Plum, Rose, Peach.
  • Epigynous: These flowers have an inferior ovary i.e. gynoecium below other floral whorls. Eg: Guava, Cucumber, and Ray florets of sunflowers.
  • Gamosepalous: When sepals are united together.
  • Polysepalous: When the sepals are free from each other.
  • Polypetalous: When the petals are united together.
  • Epipetalous: When the stamens are attached to the petals. 
  • Epiphyllous: When the stamens are fused with the tepals i.e. perianth.
  • Polyandrous: When the sepals are free from each other.
  • Mono/ Di/ Tri adelphous: When the sepals are grouped in one, two, and three bundles respectively.
  • Apocarpous: When the petals are free from each other.
  • Syncarpous: When the petals are fused together.

Floral Formulas of Some Important Families

  • Solanaceae: ⊕ ⚥ K(5) C(5) A5 G(2)
  • Liliaceae: Br ⊕ ⚥ P(3+3) A3+3 G(3)
  • Fabaceae: % ⚥ K(5) C1+2+(2) A(9)+1 G1

Also Read

FAQs on Semi-technical Description Of A Typical Flowering Plant

Question 1: How are fusion and adhesion of floral whorls indicated in a floral diagram?

Answer:

Fusion is indicated by enclosing the figure within brackets. Adhesion is indicated by drawing a line above the symbol of the floral parts.

Question 2: How is the position of the mother axis represented?

Answer:

The position of the mother axis to the flower is represented by a dot on top of the floral diagram.

Question 3: Explain the features of flowering plants.

Answer:

The main feature of a flowering plant is the presence of flower in it which have stamen which is the reproductive organ in plants. From this the pollen grain are produced which carry genetic material for the next generation. Without the presence of flowers, reproduction is not possible which is why the presence of flowers in flowering plants is mandatory.

Question 4: Define Gamosephalus.

Answer:

Flower sepals are united together known as gamosephalus.

Question 5: Give some examples of the modification of stem with their function.

Answer:

  • Stem is modified to store food example-Potato, Ginger
  • Stem turns into tendrils to help in climbing. Example-Pumpkins, Cucumber
  • Stem turn into a flattened branch or stem-joint resembling and functioning as a leaf Example- Opuntia, Euphorbia

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