हिंदी
Tamil Nadu Board of Secondary EducationHSC Science Class 11

Plant Growth Regulators

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Topics

Estimated time: 3 minutes
  • Auxins
  • Gibberellins
  • Cytokinins (Cytos – cell, Kinesis – division)
  • Ethylene (Gaseous Phytohormone)
  • Abscisic Acid (ABA) (Stress Phyto hormone)
CBSE: Class 12

Key Points: Plant Growth Regulators

  • PGRs (phytohormones) are classified into two groups - growth promoters (auxins, gibberellins, cytokinins) and growth inhibitors (abscisic acid, ethylene).
  • Growth promoters help in cell division, enlargement, flowering, fruiting and seed formation; growth inhibitors respond to stress and control dormancy and abscission.
  • Auxin - discovered by Charles & Francis Darwin (phototropism in coleoptiles), isolated by F.W. Went. Gibberellins - discovered from "bakanae" disease in rice by E. Kurosawa.
  • Cytokinins - discovered by F. Skoog through tobacco stem callus, identified as kinetin. ABA - identified in the mid-1960s from inhibitors by independent researchers.
  • Ethylene - discovered by H.H. Cousins, the only gaseous PGR
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