What is the leaf and its parts
Answers
Answer:
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Explanation:
Leaves have two main parts: The leaf blade and the Stalk or the petiole.
The leaf blade: It is also called the lamina. It’s generally broad and flat. It is in this layer that photosynthesis occurs. It contains a prominent midrib at the center of the leaf blade which is the main vein. From this midrib arise branches called veins. They are of different types depending upon the type of edges, the pattern of the veins and the number of blades per leaf.
The petiole: It is the stalk-like structure which connects the leaf blade to the stem. The petiole has tiny tubes, that connect the veins on the leaf blade to the stem. Few of these enable water transport to the leaf while the other carry food away from the leaf to other parts of the plant.
Some plants also contain another part called stipules. These are small flap-like structures that grow at the base of the petioles. They are protective in some plants when they protect the growing petiole while in others, they fall off once the petiole starts growing.
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Types of Leaves
Leaves can be classified based on many anatomic and morphologic features:
Based on Blade
Simple Leaf- the lamina or the leaf blade is undivided. Even if there are small divisions, they do not reach the midrib and divide the lamina.
Compound Leaf- The leaf blade is divided from the midrib into two or more parts. Sometimes these divided parts function as separate leaves.
Based on Shape of the Blade
Elliptical
Lanceolate
Linear
Ovate
Cordate
Want to know about Plant Tissues ?
Based on the presence or absence of the petiole (stalk)
Petiolated- These leaves have a stalk or petiole which attaches them to the stem.
Sessile- These leaves do not have a petiole and are directly attached to the stem.
Based on the serration on the edge of the leaf blade
Smooth: This type of leaf margin is called ‘entire’ leaf margin and is smooth all around
Sinuate: Have smooth curves along the margins
Dentate: They have teethed margins
Serrate: Have saw-teeth shaped margins
Lobed: the leaf blade is divided but the division doesn’t reach the midrib
Based on the arrangement of veins
Parallel: The veins on the leaf blade run parallel to each other maintaining the same distance throughout.
Palmate: The veins originate at a point and diverge from the point similar to the palm of the hand
Pinnate: There is a midrib which is present in the middle of the leaf blade. From this midrib arise the lateral veins.
Based on their arrangement on the stem
Alternate: Each leaf arises from a separate node on the stem at different levels
Opposite: Each node gives rise to two leaves, one on each side placed oppositely.
Whorled: In this arrangement, several leaves are present at the same level around the stem giving it a whorled appearance.
Rosulate: The leaves arrange themselves in a ring-like pattern around the stem.