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Biology: Plant Physiology: Absorption by Roots, Osmosis, & the Ascent of Sap (NOTES) Compiled by Akil |Helpline for ICSE Students (Class 10) Absorption by Roots, Osmosis, and the Ascent of Sap Roots and leaves are the main absorbing organs of the plant. Roots absorb water and minerals from the soil Leaves take in O2 & CO2 from the atmosphere Reasons why plants need water: a) Turgidity Cell sap in vacuoles lends rigidity to the plant b) Manufacture of food Water is used as a raw material in photosynthesis along with CO2 c) Translocation Minerals absorbed by roots and carbohydrates prepared by leaves are transported in solution form d) Cooling of plant When excess water is removed (by transpiration), the plant cools Minerals and their Functions: a) Nitrogen protein synthesis; growth b) Magnesium and iron synthesis of chlorophyll c) Potassium constituent of protoplasm; maintains osmotic balance in the cell; opening and closing of stomata d) Phosphorus promotes nuclear and cell division e) Calcium maintains the semi-permeability of the cell membrane f) Sulphur constituent of amino acid (cysteine) g) Zinc leaf formation These minerals are taken in the form of ions/radicals; (Nitrogen absorbed as nitrates) Functions of Roots: i. Fix the plant in soil ii. Absorb water and minerals from the soil iii. Conduct the absorbed substances through its tissues to the upper parts of plant Adaptations of Roots: i. Branching nature provides large surface area ii. Thin, freely permeable cell wall allows movement of minerals in and out of cell by diffusion iii. Semi-permeable cell membrane permits entry of water and restricts entry of salts by osmosis iv. Concentration of H2O in cell sap in root hair is less than that of soil helps in absorption of water by osmosis Visit us at https://icsehelpline101.wordpress.com | Connect @icsehelpline101
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