Explanation:
The small diameter of the tracheary elements increases capillarity.

Capillarity:
Capillarity is the phenomenon of a liquid rising or falling in a narrow tube due to the combination of adhesive and cohesive forces. It is also known as capillary action.

Adhesion and Cohesion:
Adhesion refers to the attraction between molecules of different substances, while cohesion refers to the attraction between molecules of the same substance.

Tracheary Elements:
Tracheary elements are specialized cells found in the xylem tissue of plants. They are responsible for the transport of water and minerals from the roots to the rest of the plant.

Increased Capillarity:
The small diameter of the tracheary elements increases capillarity for the following reasons:

1. Narrow Tube: The small diameter of the tracheary elements creates a narrow tube-like structure. This narrowness allows for a higher rise of liquid due to capillary action. The narrower the tube, the higher the capillary rise.

2. Adhesive Forces: Adhesive forces play a crucial role in capillarity. The small diameter of the tracheary elements increases the surface area available for adhesion with water molecules. The adhesive forces between the tracheary elements and water molecules pull the liquid upward, contributing to capillarity.

3. Cohesive Forces: Cohesive forces also contribute to capillarity. The small diameter of the tracheary elements increases the proximity of water molecules to each other. This proximity enhances the cohesive forces between water molecules, allowing them to climb up the narrow tracheary elements.

4. Surface Tension: Surface tension is the cohesive force between the molecules at the surface of a liquid. The small diameter of the tracheary elements increases the surface tension of water, making it easier for the liquid to rise against gravity.

Therefore, the small diameter of the tracheary elements increases capillarity by increasing the surface area available for adhesion, enhancing the cohesive forces between water molecules, and promoting surface tension.