1. Cell Walls:

* Composition: Cell walls are made up of cellulose, hemicellulose, and pectin. Cellulose fibers are strong and rigid, providing the main structural support. Hemicellulose acts as a glue, binding cellulose fibers together, while pectin adds flexibility.

* Function: Cell walls surround each plant cell, forming a strong and interconnected network that provides the plant with its shape and helps it stand upright.

2. Turgor Pressure:

* Concept: Turgor pressure is the internal pressure exerted by the fluid within the plant cells against the cell walls. This pressure is generated by the movement of water into the plant's cells.

* Function: Turgor pressure helps maintain the rigidity of the plant. When water is abundant, cells are full and firm, contributing to the plant's overall stiffness. Conversely, when water is scarce, cells lose turgor, causing the plant to wilt.

Other factors that contribute to plant rigidity:

* Xylem: This vascular tissue transports water throughout the plant, and its rigid structure also contributes to the plant's overall support.

* Sclerenchyma cells: These specialized cells have thick secondary cell walls and provide structural support, particularly in stems and leaves.

* Lignin: This complex polymer is deposited in the cell walls of certain plant tissues, providing additional strength and rigidity.

The combination of these factors gives plants their characteristic rigidity, allowing them to grow tall and support their weight.