It's some change in the conditions around the organism, which the organism can detect and respond to. A change in temperature, more light, or something physically poking the organism are examples.
Answer:
Carbohydrates may be defined as the polymers of the sugars and one of the most important biomolecule of the living organisms. Carbohydrates plays an important structural and functional role.
Carbohydrates are always present on the exoplasmic surface of the plasma membrane. The are present in the association with the proteins and lipids as glycoproteins and glycolipids. These carbohydrates acts as the signaling molecule that display information on cell surface.
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Hydrocarbons,polycyclic aromatic hydrocarbons
The root cap??? I think not for sure though.
