Lesson Plan BIOLOGY Std. -X I. Concept Study of the Leaf structure & Phyllotaxy in plants . Purpose. Awareness about the structure of a typical leaf & the types of Phyllotaxy in plants for their mode of arrangement. Category & Time. Medium 40-45 minutes. Learning Outcomes.
Lesson PlanBIOLOGYStd. -XI
Study of the Leaf structure &Phyllotaxy in plants.
Awareness about the structure of a typical leaf & the types of Phyllotaxy in plants for their mode of arrangement
Student’s awareness about the –
* Typical leaf structure
* Essentiality of various leaf parts in a plant
* Familiarity about Phyllotaxy in plants
Q. Give the definition of leaf.
Q. What do you call the structure by which leaf is attached at plant?
Q. Give the technical term for the mode of arrangement of leaves on plant.
Q. How many types of arrangement of leaves in plants are there/
Definition of Leaf
Leaf is the flattened outgrowth of Stem or a branch that develops at node & has a bud in it’s axil. These are the dissimilar organs & are meant primarily for Photosynthesis, Respiration & Transpiration.
Parts of the Leaf
1. Leaf Base2. Petiole3. Lamina
The part of leaf attached to the stem or branch is called- Leaf base. It protects a Bud in it’s axil.
The part of leaf that connects the lamina with stem, is called leaf petiole. Some time a leaf may not have a petiole, such leaves are called – Sessile otherwise the leaf is called Petiolate.
It is the flat, expended & broad part of leaf with framework of veins & veinlets. The lamina is the most important part of the leaf as it is the seat of food manufacturing in plant.
It is the mode of arrangement / distribution of leaves on stem or it’s branch.
Phyllotxy ensures that leaves may receive maximum sunlight for photosynthesis.
In such case only one leaf is attached at each node. The leaves are so arranged that a line drawn on the stem through the leaf bases will take a spiral course. Ex. Hibiscus, Brassica etc.
In such case two leaves are present at each node, standing opposite to each other. It is of two subtypes -
Here pairs of leaves at each successive node are placed at right angle to each other. Eg. Ocimum, Calotropis etc.
Here pairs of leaves at each successive node are placed over each other in same plane. Eg.Eugenia,Quisqualis etc.
In this type more than two leaves are present at each node, forming a whorl. Ex. Oleander, Alstonia etc.
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