In plants, mucilages are substances that serve various functions such as lubrication, protection, and adherence. They are produced by specialized cells called mucilage cells. The correct answer for the given question is option 3: polysaccharides.

Polysaccharides are long chains of sugar molecules. Mucilages are primarily composed of polysaccharides such as pectin, hemicellulose, and cellulose. These polysaccharides form a gel-like substance when they come into contact with water. This gel-like property of mucilages helps plants in several ways.

Firstly, mucilages act as lubricants. They provide a slippery surface for plant parts such as roots to move easily through the soil. This reduces friction and allows roots to penetrate the soil efficiently.

Secondly, mucilages act as protective agents. They can form a coating around seeds, protecting them from desiccation, pathogens, and predators. This coating also helps seeds adhere to surfaces such as soil, ensuring better germination and establishment.

Therefore, polysaccharides are the main constituents of mucilages in plants. They play essential roles in plant growth, development, and survival.