Before telling you what are the main functions of polysaccharides in plants, I would like to mention polysaccharides first. Polysaccharides are carbohydrates that mean hydrates of carbon. The simplest formula for carbohydrates is Cn(H2O)n, where n can be 3 or more than 3. The simplest carbohydrates are glyceraldehyde and dihydroxyacetone.
Glyceraldehyde and dihydroxyacetone, are triose but one is aldose and the next is ketose respectively. They are named according to the number of carbon and the type of carbonyl group present in the molecule. Such as triose, tetrose, pentose, and hexose. These are the simple sugar/carbohydrates that are the building blocks of complex carbohydrates such as polysaccharides.
Polysaccharides (poly + saccharides) are polymeric carbohydrates that are mainly composed of hexoses and some pentoses and their modified forms such as acids, amides, phosphorylated and sulfated forms. These subunits are linked to each other with glycosidic bonds (an ether bond that involves a central oxygen atom connecting two carom atoms).
Main functions of carbohydrates in plants
Now, let’s come to the main point. So, what are the main functions of polysaccharides in plants? The main functions of polysaccharides in plants are protection and energy. If you look carefully, plant cell walls are made up of cellulose and hemicellulose. These two are the major plant polysaccharides that provide rigidity and physical strength to the cell wall and the whole plant. In the same way, plants produce starch, a polysaccharide that is considered an energy reserve for them.
Starch is mainly used for energy production that fuels the growth and development of plants. Cellulose is a polymer of 1→4 linked β-D-Glucose units, in the same way, starch is a 1→4 linked α-D-Glucose with some branches at 2 (2→6 linkages).
Cellulose is a polymer of 1→4 linked β-D-Glucose units, in the same way, starch is a 1→4 linked α-D-Glucose with some branches at 2 (2→6 linkages). Hemicellulose is most similar to that cellulose but it has many side branches of some pentoses. To know more about hemicellulose visit the main post.
There are some other polysaccharides in plants that are less abundant but have some important functions such as protection against pathogens. Among those types of polysaccharides, the gum is the one that is secreted from the plant around the cut/wound area to prevent bacterial and fungal attacks.