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Life Processes in Plants - Transport in Plants

Grade 7CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Plants have a specialized vascular system for the transport of substances, consisting of two main types of tissues: Xylem and Phloem.

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The Xylem tissue is responsible for the upward transport of water and dissolved minerals from the roots to the leaves. This movement is typically unidirectional.

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Root hairs increase the surface area of the roots, allowing for more efficient absorption of H2OH_{2}O and minerals from the soil through the process of osmosis.

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Osmosis is the movement of water molecules from a region of higher water concentration to a region of lower water concentration through a semi-permeable membrane.

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Transpiration is the evaporation of water in the form of vapor through the stomata present on the surface of leaves. This process creates a 'transpiration pull' or suction force that helps in the ascent of sap.

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Phloem is responsible for the transport of synthesized food (glucose/sucrose) from the leaves to all other parts of the plant, including roots and storage organs. This bidirectional process is called translocation.

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Transpiration also helps in cooling the plant body, similar to how sweating cools the human body.

📐Formulae

Rate of Transpiration=Volume of water lost (ml)Time taken (h)Rate\ of\ Transpiration = \frac{Volume\ of\ water\ lost\ (ml)}{Time\ taken\ (h)}

Water Absorption Rate=Total volume of water absorbedTotal timeWater\ Absorption\ Rate = \frac{Total\ volume\ of\ water\ absorbed}{Total\ time}

C6H12O6+6O2→6CO2+6H2O+Energy (ATP)C_{6}H_{12}O_{6} + 6O_{2} \rightarrow 6CO_{2} + 6H_{2}O + Energy\ (ATP)

💡Examples

Problem 1:

A potted plant was weighed at the start of an experiment and found to be 1500 g1500\ g. After 55 hours in the sun, the plant was weighed again and found to be 1425 g1425\ g. Calculate the rate of water loss due to transpiration in g/hg/h.

Solution:

Total water lost=1500−142575Total\ water\ lost = \begin{array}{r} 1500 \\ - 1425 \\ \hline 75 \end{array} Rate=75 g5 h=15 g/hRate = \frac{75\ g}{5\ h} = 15\ g/h

Explanation:

The decrease in weight of the potted plant is primarily due to the loss of water through transpiration. By dividing the total weight loss by the time elapsed, we find the hourly rate of transpiration.

Problem 2:

Identify the direction of movement of water if Cell A has a water concentration of 95%95\% and Cell B has a water concentration of 85%85\%.

Solution:

Water will move from Cell A to Cell B because 95%>85%95\% > 85\%.

Explanation:

According to the principle of osmosis, water moves from an area of higher concentration (95%95\% in Cell A) to an area of lower concentration (85%85\% in Cell B).