The Genetic Basis of Growth and Development

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The Genetic Basis of Growth and Development
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Plants are made up of

• cells
• tissues
• organs

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Plants have specialized tissues called meristems

• Shoot apical meristem (SAM)
• Intercalary meristem
• Root apical meristem (RAM)
• Lateral meristems pericycle, vascular cambium

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Plants grow by cell

• division
• expansion
• differentiation

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Plant development is controlled by hormones

• Auxinstimulates growth and cell division
• Gibberellinsstimulates stem growth and seed
  germination
• Cytokininsregulates cell division and senescence
• Abscisic Acidresponds to osmotic stress,
  inhibits germination, closes guard cells

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More Hormones

• Ethyleneregulates fruit ripening and flowering,
  responds to stress
• Jasmonic Acidresponds to insect attacks turning
  on plant defenses
• Brassinosteroids affect stem elongation, pollen
  tube growth, leaf bending and xylem
  differentiation

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Plant development is affected by the environment

• Phototropism (light)
• Gravitropism (gravity)
• Thigmotropism (touch)
• Nyctinastic movement (light)
• Thigmonastic movement (mechanical)

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Environmental Influences

• Circadian Rhythms (biological clocks set by
  light)
• Dormancy (temperature, light water)
• Vernalization (cold induction of flowering)
• Stratification (cold induction of germination)
• Photoperiodism (germination and flowering)

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Photoperiodic regulation of flowering
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Genetic control of flowering
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Signal transduction by hormones or environmental
signals
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Genetic modification can redirect developmental
processes

• Male sterility for hybrid seed production
• Fruit ripening
• Senescence
• Delaying seed pod splitting
• Flowering