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NEET Biology Plant Growth and Development

Plant Growth and Development PDF Notes, Important Questions and Synopsis


  • Growth is an increase in the size of an organism or part of an organism, usually as a result of an increase in the number of cells.
  • An auxanometer is used to measure the rate of growth in terms of shoot length.
  • Phases of Growth

  • Growth rate is the number of individuals added per thousand individuals which is represented by a growth curve.
  • The population growth curve is of two types—arithmetic growth and geometrical growth [sigmoid growth curve (S-shaped)]
  • Totipotency is the ability of a single cell to divide and develop into a new organism.
  • A growth regulator or phytohormone is an organic substance produced naturally in plants controlling growth and other functions.

  • Physiological Effects of Plant Growth Regulators




    • Promotes the elongation and the growth of stems and roots.

    • Promotes cell division in vascular cambium.


    • Cause stem elongation and leaf expansion but have no effect on roots.

    • Break dormancy of buds and tubers.

    • Used to promote elongation of internodes in sugarcane.


    • Stimulate cell division and prevent the onset of senescence in tissues.

    • Promote the growth of lateral buds.

    • Break dormancy of seeds.




    • Inhibits the growth of lateral buds and causes apical dominance.

    • Breaks the dormancy of buds and seeds.

    Abscisic Acid

    • Induces and maintains dormancy in many seeds.

    • Inhibits cell division and cell elongation.

  • The response of plants to the relative lengths and alternations of light and dark periods with respect to the initiation of flowering is called photoperiodism.

  • Vernalisation is a method of inducing early flowering in plants by pre-treatment of their seeds at low temperature.