Maximal size in terms of wall thickening and protoplasmic modification are achieved by:

The cells of maturation zone, attain their maximal size in terms of wall thickening and protoplasmic modifications.Cells in meristematic phase of growth are rich in protoplasm, possess large conspicuous nuclei. Their cell walls are primary in nature, thin and cellulosic with abundant plasmodesmata connections. Increased vacuolation, cell enlargement and new cell wall deposition are the characteristics of the cells in elongation phase. There is no reductional phase in plant growth.