Q.Describe the three phases of plant growth (meristematic, elongation and maturation) with reference to the cellular changes -- in cytoplasm density, vacuolation and cell wall -- that mark each phase.

[!TLDR]

Meristematic = dense cytoplasm, dividing; elongation = vacuolation and enlargement; maturation = reduced protoplasm, thickened/specialised wall.

[!ANSWER]

Meristematic phase: small, dense cytoplasm, thin wall, actively dividing. Elongation phase: increasing vacuolation, cell enlargement, new wall deposited. Maturation phase: enlargement stops, protoplasm proportionally reduced, wall often further thickened/specialised.

In the meristematic phase, located right at the root or shoot apex, cells are small, packed with dense cytoplasm relative to their size, possess thin cellulosic walls with abundant plasmodesmatal connections, and are actively dividing by mitosis -- vacuolation at this stage is minimal or absent. In the elongation phase, immediately behind the meristem, cells stop dividing and instead enlarge considerably, chiefly through the uptake of water into an expanding central vacuole (which comes to occupy an increasing proportion of the cell's volume), while new cell wall material is synthesised and deposited to accommodate this expanding volume. In the maturation phase, cell enlargement finally stops, the vacuole occupies most of the cell's volume so that the living protoplasm is now proportionally much reduced compared to the meristematic stage, and the cell wall is frequently further thickened and chemically modified (for example, lignified in the case of a tracheary element) as the cell settles into its final, specialised, functional form.

[!ANSWER]

Meristematic phase: small, dense cytoplasm, thin wall, actively dividing. Elongation phase: increasing vacuolation, cell enlargement, new wall deposited. Maturation phase: enlargement stops, protoplasm proportionally reduced, wall often further thickened/specialised.

Work through the three phases in sequence, describing for each the specific state of the cytoplasm, vacuole and cell wall that distinguishes it from the phase before and after.

Describing vacuolation as occurring in the meristematic phase -- extensive vacuolation is specifically the hallmark of the elongation phase, not the actively dividing meristematic phase.