Tissues in Action | Class 9 Science Notes

Transport of Substances in Plants

Transport in plants involves the movement of water, minerals, and food to different parts. Water and minerals are absorbed by roots and transported through xylem vessels to the leaves and other parts. This movement is mainly unidirectional, from roots to leaves. The process of water movement involves root pressure, capillary action, and transpiration pull. Transpiration, the loss of water vapor from leaves, creates a suction force that pulls water upward through the xylem.

Food manufactured in the leaves by photosynthesis is transported through phloem to all parts of the plant, including growing regions and storage organs. This movement is bidirectional and is called translocation. The pressure flow hypothesis explains how food moves in the phloem: sugars are actively loaded into sieve tubes, drawing water by osmosis, creating pressure that pushes the food along.

The efficient transport system in plants ensures that all cells receive water, minerals, and food necessary for metabolism and growth. Any disruption in this system affects plant health and productivity.

📊 Diagram: Diagrams illustrate the upward movement of water through xylem vessels driven by transpiration pull and root pressure. Another diagram shows the bidirectional flow of food through phloem sieve tubes, explaining the pressure flow mechanism.

🧪 Activity: Experiment to observe transpiration by placing a leafy twig in water and noting water uptake.

🔗 Connection: This section connects to the study of animal tissues, where transport and movement are also essential functions.