Why is the leaf called the main organ of the plant? What is the role of the layered arrangement of leaves on the stem?

The leaf is the main organ of the plant due to the fact that it is there that the synthesis of the necessary organic substances occurs. This is possible thanks to chloroplasts. They create complex organic glucose molecules from inorganic substances under the influence of sunlight. Further, these substances diverge along the sieve tubes to those parts of the plant where the cells do not have chloroplasts. Also, organic matter can be stored in the root or stem of the plant. This is how a plant can live when photosynthesis is impossible or is slow.