Leaf and its Parts: The leaf is a lateral generally flattened structure borne on the stem. The leaves develop from the nodes. Their main function is photosynthesis and food making, axillary buds are found in its axil. All the leaves of a plant is known as phyllome. Axillary bud later develops into a branch. Leaves originated from shoot apical meristem and are arranged in acropetal order.

Leaf and its Parts

Leaf is divided into 3 main parts:

Leaf base (Hypopodium)

• Leaves are attached to stem by leaf base.
• In some plants, leaf base becomes swollen and is called pulvinus which is responsible for sleep movement e.g., Cassia, mimosa, bean.
• In some plants, leaf base expands into sheath (Sheathing leaf base), e.g., grasses and banana (monocots).
• When the leaf base partially encloses the stem, it is called semi amplexicaul e.g., Prickly poppy, Calotropis procera (Madar).
• It completely encloses the stem, it is called amplexicaul e.g., Sonchus, Polygonum.

Petiole (Mesopodium)

• The part of leaf connecting the lamina with the branch of stem. Petiole help to hold the blade to light.
• In Eichhornia petiole swell and in citrus it is winged.
• Petiole is modified in tendrils in Nepenthes.
• In Australian acacia petiole is modified in phyllode.
• Long thin flexible petiole allow leaf blade to flutter in air, thereby cooling the leaf and bringing fresh air to leaf.

Lamina (Epipodium): It is a broad and flattened part of leaf. Its main functions are photosynthesis and transpiration. Shape of lamina are:

• Acicular – Lamina is long and pointed, like a needle. eg. Pinus
• Lanceolate – In this type lamina is pointed or narrower at the ends while broader in the middle. eg. Bamboo,  Nerium
• Linear – The lamina is long and narrow having parallel margins. eg. Grass
• Ovate – In this type lamina is egg-shaped having broad base with slight narrow top. eg. Ocimum,
  Banyan, China rose.
• Cordate – Its shape is like a heart. eg. Betel.
• Oblong – Long and broad lamina. eg. Banana
• Sagittate – The lamina is triangular in shape. eg. Sagittaria
• Spathulate – The lamina is broad spoon shaped. eg. Calendula
• Orbicular or Rotund – In this types the lamina is spherical. eg. Lotus.
• Elliptical or Oval – In this type the middle part of lamina is broad while the ends are narrow and oval. eg. Guava.
• Oblique – In this types midrib divides, lamina into two unequal halves. eg. Bignonia, Neem.

Follow on Facebook

By Team Learning Mantras