Class 11 Biology Chapter 13 Plant Growth and Development – Revision Notes

Plant growth follows a sigmoid curve through lag, log, and stationary phases in this chapter, which also covers the five major hormones and how day length and cold exposure affect flowering.

Last Updated: September 23, 2026

Growth Characteristics

• Indeterminate, open growth; sigmoid curve: lag, log, stationary phases.
• Phases: meristematic, elongation, maturation.

Plant Hormones

• Auxin: elongation, apical dominance.
• Gibberellin: stem elongation, germination.
• Cytokinin: cell division, delays senescence.
• Ethylene: fruit ripening (only gaseous hormone).
• ABA: stress hormone, dormancy, stomatal closure.

Photoperiodism & Vernalisation

• Flowering response to day/night length (short-day, long-day, day-neutral).
• Vernalisation: flowering promoted by cold exposure.

One-Line Summary

Plant growth is indeterminate and follows a sigmoid pattern, regulated by five major phytohormones (auxin, gibberellin, cytokinin, ethylene, ABA) along with photoperiod and temperature cues controlling flowering.

Frequently Asked Questions

What are plant growth hormones, and why are they important?
Plant growth hormones, or phytohormones, are naturally occurring chemical substances that regulate growth and development, such as cell division, elongation, flowering, and stress response, even in extremely small concentrations.

What is the difference between growth and differentiation in plants?
Growth refers to an irreversible increase in size or mass due to cell division and elongation, while differentiation refers to the process by which cells become structurally and functionally specialised for specific roles.

Written by Satish

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