Lesson 3 of 13 · 6 min
Phases of growth
NCERT §13.1.3
Kavya grows a bean seedling on wet tissue and draws ink lines along its root. Two days later the lines have moved apart, but not evenly. Where did the root actually grow?
The lesson in notes
In short
Growth is divided into three phases: meristematic, elongation and maturation. A root tip shows all three in order from the apex backwards.
Meristematic phase: the constantly dividing cells at the root apex and shoot apex. They are rich in protoplasm, have large conspicuous nuclei, and thin primary cellulose walls with plenty of plasmodesmata.
Elongation phase: the cells just behind the meristematic zone. They show increased vacuolation, cell enlargement and deposition of new cell wall.
Maturation phase: further from the apex, behind the elongation zone. The cells reach their maximum size in wall thickening and protoplasmic change; most familiar tissue types belong here.
The zone of elongation can be found with the parallel line technique: marks drawn at equal spacing on a root tip spread apart most in the zones just behind the apex.