• A plant is a living organism that produces food for themselves and acts as the primary source of nutrition for all life forms on earth.
  • They grow on mountains, in valleys, in deserts, in fresh and salt water – almost everywhere on the planet. Plants come in all shapes and sizes from the smallest seedling to the towering Giant Sequoias.

Plant Parts and their Functions

  • Broadly, plants have two organ systems: A) the root system and B) the shoot system. A typical diagram of a plant body consists of these parts: roots, stems, leaves, flowers, and fruits.
  • The root system covers the underground parts of a plant, which include the roots, tubers, and rhizomes, whereas the shoot system consists of parts found above the ground, such as leaves, stems, flowers, and fruits.
Plant Parts and Their Functions

The Root

  • The main functions of the root system are absorption of water and minerals from the soil, providing a proper anchorage to the plant parts, storing reserve food material and synthesis of plant growth regulators.
  • In majority of the dicotyledonous plants, the direct elongation of the radicle leads to the formation of primary root which grows inside the soil. It bears lateral roots of several orders that are referred to as secondary, tertiary, etc. roots. The primary roots and its branches constitute the tap root system, as seen in the mustard plant.
  • In monocotyledonous plants, the primary root is short lived and is replaced by a large number of roots. These roots originate from the base of the stem and constitute the fibrous root system, as seen in the wheat plant.
  • In some plants, like grass, Monstera and the banyan tree, roots arise from parts of the plant other than the radicle and are called adventitious roots.
  • The root is covered at the apex by a thimble-like structure called the root cap. It protects the tender apex of the root as it makes its way through the soil.
  • Tap roots of carrot, turnip and adventitious roots of sweet potato, get swollen and store food.
  • Hanging structures that support a banyan tree are called prop roots. Similarly, the stems of maize and sugarcane have supporting roots coming out of the lower nodes of the stem. These are called stilt roots.
  • In some plants such as Rhizophora growing in swampy areas, many roots come out of the ground and grow vertically upwards. Such roots, called pneumatophores, help to get oxygen for respiration.
The Root

The Stem

  • The region of the stem where leaves are born are called nodes while internodes are the portions between two nodes.
  • Some stems perform the function of storage of food, support, protection and of vegetative propagation.
  • Underground stems of potato, ginger, turmeric, zaminkand, colocasia are modified to store food in them.
  • Stem tendrils which develop from axillary buds, are slender and spirally coiled and help plants to climb such as in gourds (cucumber, pumpkins, watermelon) and grapevines.
  • Axillary buds of stems may also get modified into woody, straight and pointed thorns. Thorns are found in many plants such as Citrus, Bougainvillea. They protect plants from browsing animals.
  • Some plants of arid regions modify their stems into flattened (Opuntia), or fleshy cylindrical (Euphorbia) structures. They contain chlorophyll and carry out photosynthesis.
  • Underground stems of some plants such as grass and strawberry, etc., spread to new niches and when older parts die new plants are formed.

The Leaf

  • Leaves originate from shoot apical meristems. Leaf develops at the node and bears a bud in its axil. The axillary bud later develops into a branch.
  • A typical leaf consists of three main parts: leaf base, petiole and lamina.
    • The petiole help hold the blade to light. Long thin flexible petioles allow leaf blades to flutter in wind, thereby cooling the leaf and bringing fresh air to leaf surface.
    • The lamina or the leaf blade is the green expanded part of the leaf with veins and veinlets. There is, usually, a middle prominent vein, which is known as the midrib. Veins provide rigidity to the leaf blade and act as channels of transport for water, minerals and food materials.
  • Functions:
    • Making food for the plant with the help of sunlight, carbon dioxide, and water through photosynthesis
    • Helping in reproduction such as in Bryophyllum, a group of sprout leaf plants
    • Helping in evaporation from the aerial parts of the plant by transpiration
    • Apart from these main functions, leaves of some plants are modified to form tendrils, that help in climbing (e.g., pea plant) or spines, helping in protection (e.g., cactus).
    • Some leaves may turn fleshy to store food (e.g., onion plant).
Parts of Plants

Leaf Venation

  • The arrangement of veins and the veinlets in the lamina of leaf is termed as venation.
  • When the veinlets form a network, the venation is termed as reticulate. When the veins run parallel to each other within a lamina, the venation is termed as parallel.
  • Leaves of dicotyledonous plants generally possess reticulate venation, while parallel venation is the characteristic of most monocotyledons.

The Flower

  • They are the most colorful and attractive parts of a plant. A flower contains four main parts:
    • Sepals: Green parts of a flower found below the petals that protect flower buds from injury.
    • Petals: Colorful parts of a flower found above the sepals that help in pollination.
    • Stamens: Consists of an anther and a filament. They are the male reproductive part of a plant producing male sex cells or spermatia.
    • Carpel: Consists of stigma, style, and ovary. They are the female reproductive part of a plant producing female sex cells or ovules.
  • The flower is the reproductive unit in the angiosperms. It is meant for sexual reproduction.
  • Androecium and gynoecium are reproductive organs. When a flower has both androecium and gynoecium, it is bisexual. A flower having either only stamens or only carpels is unisexual.
  • Aestivation: The mode of arrangement of sepals or petals in floral bud with respect to the other members of the same whorl is known as aestivation.
Parts of Flower

Androecium

  • Androecium is composed of stamens. Each stamen which represents the male reproductive organ consists of a stalk or a filament and an anther. Each anther is usually bilobed and each lobe has two chambers, the pollen-sacs. The pollen grains are produced in pollen-sacs. A sterile stamen is called staminode.

Gynoecium

  • Gynoecium is the female reproductive part of the flower and is made up of one or more carpels. A carpel consists of three parts namely stigma, style and ovary.
  • After fertilization, the ovules develop into seeds and the ovary matures into a fruit.
  • Placentation: The arrangement of ovules within the ovary is known as placentation.

The Fruit

  • The fruit is a characteristic feature of the flowering plants. They are the ripened ovary found in flower after fertilization. The ovules after fertilization make the seed, which is then fertilized to form new plants.
  • It is a mature or ripened ovary, developed after fertilisation.
  • If a fruit is formed without fertilisation of the ovary, it is called a parthenocarpic fruit.
  • The Seed: The ovules after fertilisation, develop into seeds.
Parts of Fruit

Seed

  • Seeds contain plant material that can develop into another plant. This plant material is called an embryo.
  • Seeds are covered with a protective seed coat and have one or two cotyledons.
    • Cotyledons are the food for the baby plant until it can make its own food from light and are often the first embryonic leaves of the plant.
Parts of Seed
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