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Chapter 7 Getting to know plants Notes




Classification of Plants


Plants can be classified into various categories depending on various features.
  • On the basis of FLOWER
  1. Flowering also called Angiosperms : Sun flower, Rose, tomato
  2. Non- Flowering also called Gymnosperms: Pines,ferns,mosses.
  • On the basis of their Size, Type of Stem, spread of branch, plants are classified into 3 categories:
  1. Herbs
  2. Shrubs
  3. Trees
Characteristics
Herbs
Shrubs
Trees
Size
Short plants with height less than 1m
Medium-sized plants with height around 1-3m
Tallest plant with height more than 3-4 m
Nature of stem
Green and tender stem, have a few branches
Hard & woody stem, not very thick.
Thick
Type of branches
Branches are either absent or present sparsely
Branches arise from the base of the stem giving it a bushy apperance
Branches arise from the upper part of the stem at some distances from the ground. Some trees like coconut tree are branch less; they have only one stem that bears leaves, flowers and fruits
Examples
mint, tomato, spinach, wheat, paddy, grass etc.
Rose, lemon, henna, hibiscus etc
Banyan, mango, neem cashew, oak etc


Certain plants have weak steams and cannot stand upright. They are categorised into two types:
Creepers
  • The stems of these plants spread/trail on the ground.
  • Stems are long, thin and fragile and cannot stand erect.
  • Examples – water melon, strawberry, pumpkin, sweet potato etc
Climbers
  • More advanced than creepers.
  • They have thin long and weak stems that cannot stand upright but they can use external support to grow vertically and carry their weight.
  • These types of plants use special structures called tendrils to climb.
  • Examples – pea plant, grapevine, money plant, etc.


SOME OTHER TYPES OF PLANTS


MOSS
  • Small non flowering green plants.
  • Grow in damp and shady areas.
GRASS
  • Flowering plants.
  • Short in height.
  • Long narrow leaves.
AQUATIC PLANTS
  • Grow in water only.
  • They are either rooted in mud under water (lotus) or float without any anchorage (water hyacinth) other e.g. water lilies, hydrilla & tape grass.


PARTS OF A PLANT


  1. Root System- Non-green part of the plant present under the ground. Contains Main root and Lateral roots.
  2. Shoot System- Present above the ground. Contains Stem, branches, leaves, flowers, buds, fruits.


ROOT SYSTEM


Tap Root
  • One thick vertical root called Primary root with many lateral roots arising from it.
  • Example: Rose, pea, Dahlia, Gram.
Fibrous Root
  • Arise as a tuft from base of stem. Usually short-lived.
  • Example: Grass, maize, wheat and rice.

FUNCTIONS OF ROOTS.

  • Absorption of water and nutrients from the soil.
  • Anchors the plant to the soil.

MODIFICATIONS OF ROOTS

Modifications- Roots performing special functions other than their normal functions. For this, they undergo few changes in their appearance.
Food storage
  • Tap roots store food for unfavourable conditions.
  • Can be eaten and are called Edible Roots.
  • Example: Carrot, beetroot, radish, sweet potato.
Extra Support
Prop Roots
  • Roots grow as pillars to support weak stem or heavy branches.
  • Example: Banyan tree.
Stilt Roots
  • Roots arise from stem to give support to weak stem.
  • Example: Maize
Climbing Roots
  • Roots help weak stems to climb up a support.
  • Example: Money Plant and Black Pepper.

SHOOT SYSTEM-STEM

  • Main part of shoot stem.
  • Bears branches, leaves, flowers, buds and fruits.
  • Stem has two main parts- Node and Internode
  • Node- Point from where leaf or a branch arises. Several nodes are present in a stem
  • Internode- Portion of stem between two nodes.

FUNCTIONS OF STEMS:

  • Keeps plant upright.
  • Helps in Transportation of water, minerals, and food to different parts.

MODIFICATIONS OF STEMS

Providing Support
  • Tender, coiled structures called tendrils coil around any support.
  • Present in weak stems. Called climbers or twiners.
  • Example: Grapevines
Food storage
  • Underground stems store food.
  • Example: Potato, onion, ginger.
Making food
  • Green and fleshy stem.
  • Can perform photosynthesis and store water.
  • Example: Cactus.


LEAF

  • Responsible for carrying out photosynthesis.
PARTS OF LEAF:
  1. Lamina – flat broad part of leaf, receives solar radiation during photosynthesis.
  2. Petiole – small stalk which attaches the lamina to the stem.
  3. Veins – lines running through the leaves, responsible for transfer of water and minerals in the leaves.
  4. Midrib – thicker line/vein in the middle of a leaf.

VENATION

  • FUNCTION OF VEINS
(a) Distributes water and minerals throughout the leaf.
(b) Gives support
  • TYPES OF VENATIONS:
  1. Parallel venation – veins run parallel to each other from the petiole to the tip of the leaf, found in the leaves of grasses, cereals (wheat, rice) and banana.
  2. Reticulate venation – several small veins/veinlets arise from the midrib, found in the leaves of mango, Hibiscus, rose, tulsi, papaya etc.

FUNCTIONS OF LEAVES

  • Photosynthesis- KITCHEN OF PLANT
  • Presence of stomata on the surface of leaves helps in gaseous exchange.
  • Transpiration – loss of water in the form of vapour from leaves. Helps in
  • Maintaining temperature.
  • Absorption of more water and minerals from the soil.

MODIFICATIONS OF LEAF.

Spines –
  1. reduces the surface area of leaves and minimizes the loss of water due to transpiration.
  2. defence mechanism of plants to prevent animals from eating them.
  3. found in desert plants.
Pitcher –
  1. Seen in insectivorous plants.
  2. Modified leaves (pitchers) capture insects to fulfil their nitrogen requirement (nitrogen is required for protein synthesis)
  3. Pitcher plants grow in nitrogen deficient soil.
  4. These plants can also make food through photosynthesis
Tendrils
  1. Tip of leaves gets modified to tendrils.
  2. Provide extra support to plants.
  3. Found in pea plant, Gloriosa, cucumber plant etc.


FLOWER

  • Modified shoot. Develops from bud.
  • Reproductive organ.
  • Attractive- Colourful petals or fragrance.
  • Develops into fruit.

STRUCTURE OF FLOWER

  • SEPAL- Outermost part. Green and leafy. Protects flower in bud stage.
  • PETAL- Colourful or white. Vary in shape and size. Attract insects and birds.
  • STAMEN- Male Reproductive part.
  • Anther- Sac like structure containing pollen grains.
  • Filament- Slender stalk like structure.
  • PISTIL/CARPEL- Female Reproductive organ.
  • Stigma- Uppermost part. Brush like appearance. Might be sticky to catch pollen.
  • Style- Middle tube like part.
  • Ovary- Lower swollen portion containing ovules. Ovary forms fruits and ovule forms seeds.
  • THALAMUS/RECEPTACLE- Swollen portion at base of flower. All parts are attached to it.
  • PEDICEL/PEDUNCLE- Stalk of the flower.

POLLINATION


  • It the transfer of pollen to a stigma, ovule, flower, or plant to allow fertilization.
  • It is of two types
SELF-POLLINATION
In self-pollination, the pollen from the anther of a flower is transferred to the stigma of the same flower or the stigma of a different flower on the same plant.
CROSS-POLLINATION
In cross-pollination, the pollen from the anther of a flower on one plant is transferred to the stigma of the flower on another plant of the same species.
After pollination
  • Ovary – forms fruit
  • Ovule – forms Seeds


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