Question

Who gave the theory of root pressure?

Answer 1

The theory of root pressure was first proposed by Stephen Hales, an English botanist and physiologist in the 18th century.

Root pressure is a positive pressure that develops in the roots of some plants, especially when transpiration is low (typically at night or in humid conditions). It helps in pushing water and minerals upwards through the xylem vessels.

Key points about root pressure:

• Definition: Root pressure is the osmotic pressure within the cells of a root system that causes sap to rise through a plant stem to the leaves.
• Mechanism: It is caused by the continuous absorption of water from the soil by root hairs through osmosis.
• Involvement of minerals: Active transport of mineral ions into the xylem lowers the water potential, causing water to enter the xylem from surrounding root cells.
• Pressure buildup: As more water enters, a pressure builds up in the xylem vessels of the root, pushing the sap upwards.
• Guttation: Root pressure is responsible for guttation – the exudation of water droplets from the edges of leaves, commonly seen in the early morning.
• Limitation: Root pressure alone cannot lift water to the tops of tall trees; it is mainly effective in herbaceous and smaller plants.

Thus, Stephen Hales is credited with the discovery and explanation of this phenomenon, making him the correct answer to the question.