Question

What are lignins , cellulose in simple permanent tissue ?

Answer 1

Animals can easily digest the contents of plant cells, but not their cell walls. All plant cells have an outer cell wall composed of cellulose or lignin.. This reduces the amount of energy animals can extract from plants, because most animals lack the specific enzymes that would allow them to digest cellulose.

Fibre is the amount of cellulose and lignin present in the plant. In general, older and woodier plants have higher levels of cellulose and lignin. Lignin cannot be digested no matter how long it remains in the digestive system. In addition, lignin interferes with gut microbes that do have the necessary enzymes to digest cellulose, because it both acts as a physical barrier to digestion, and contains chemical bonds that cannot be broken down by normal stomach microbial flora.

'Digestibility" describes how readily the plant can be digested and its energy released for use by an animal. The digestible part of a plant includes the cell contents and the small amount of fibre that can be broken down. The amount of energy available to an animal eating a plant is determined by the proportion of fibre to cell contents in that plant.