Phases of Growth

Every actively growing zone of a root or shoot passes through three sequential cellular phases before the tissue reaches full maturity. In the formative phase, small, densely cytoplasmic meristematic cells near the very tip divide repeatedly by mitosis; some daughter cells stay in this dividing pool while others move on to the next phase. In the elongation phase, the newly produced daughter cells are pushed away from the meristem and expand rapidly in volume - a process that needs a steady auxin and food supply, along with new cell-wall material being laid down (intussusception) and a large central vacuole developing. In the maturation phase, cells stop enlarging altogether and instead thicken their walls and differentiate into their final specialised form and function; once differentiation is complete, the ce …