9th class biology urdu medium pdf

9th Class Biology (Urdu Medium) Text Book by Punjab Board



 




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what is transpiration in plants?

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🌿 What is Transpiration? Transpiration is the process by which plants lose water vapor from their aerial parts , mainly through small pores called stomata present in the leaves. It is a natural and essential part of a plant’s life, similar to how sweating works in humans. In simpler words: Transpiration is the evaporation of water from plant leaves, stems, and flowers into the atmosphere. 🧩 Types of Transpiration Type Description Stomatal Transpiration Loss of water through stomata; accounts for about 90% of water loss. Cuticular Transpiration Loss of water through the waxy cuticle covering the leaf surface. Lenticular Transpiration Loss of water through tiny openings called lenticels on stems and branches. 🌟 Importance of Transpiration Cooling Effect : Transpiration helps lower the temperature of the plant, just like sweating cools the human body. Water Movement : It creates a transpiration pull that assists in transporting water and minerals from roots to leaves. ...
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What is transpiration pull?

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🌿 What is Transpiration Pull? Transpiration pull is a vital mechanism in plants that facilitates the upward movement of water from the roots to the leaves. This process is driven by the evaporation of water from the leaf surfaces, primarily through structures called stomata . 🧬 How Does Transpiration Pull Work? Water Absorption : Roots absorb water from the soil through osmosis. Cohesion and Adhesion : Water molecules stick together (cohesion) and to the walls of xylem vessels (adhesion), forming a continuous column. Evaporation : Water evaporates from the mesophyll cells into the air spaces within the leaf and exits through the stomata. Negative Pressure : The loss of water creates a negative pressure (tension) that pulls more water into the leaf from the xylem. Upward Movement : This tension pulls the continuous column of water upward from the roots through the xylem vessels to the leaves. This entire process is passive, relying on physical forces rather than ...
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