Gravity
Plant roots always grow downward because specialized cells in root caps detect and respond to gravity. This is an example of a tropism. A tropism is a turning toward or away from a stimulus in the environment. Growing toward gravity is called geotropism.
Answer:
Proteins.
Explanation:
Protein is one of the most important biomolecule of the living organisms. Proteins are made up of the polymers of the amino acids. These are the primary building block of the body.
Proteins are involved in the assembly of different molecules. Proteins are involved in the immune response initiation, the enzymatic activity and the cell signalling of the molecules.
Thus, the correct answer is option (B).
XYLEM AND PHLOEM.................
