B4. Plant Growth and Development

• Development 


  The attainment of size by virtue of growth and architectural style by morphogenesis (differentiation of cells into tissues, organs and organisms)

  Aspects

  1. Growth
  2. Differentiation
  3. Organization
• Growth 


  The irreversible increase of cell number, and essentially its dry mass or weight

  • increase in size does not mean an increase in growth.
• Growth Curve

  Cells/organs show a definite pattern of growth

  Stages of Growth

  1. Lag
  2. Logarithmic
  3. Stationary
• Differentiation

  • Reflects the orderly processes by which a genetically identical cells become different, forming specialized tissues and organs
  • The reflection of change in the cells biochemical program, controlled by developmental genes
• Dedifferentiation 


  The reversal of the cell specialization

  • Important in the repair of injury, where cell near damaged sites become TOTIPOTENT and reprogram their development
• Organization

  • orientation and integration of differentiated cells in space together with regulated growth of whole plant
• Morphogenesis

  • The orientation and integration of differentiated cells in space together with regulated growth, and the consequent attainment of form and structure of thr complete organism.
• Localization of Growth

  Essential Characteristics of organisms

  • take up relatively simple substances from environment and synthesize these to complex substances

  At Cellular level

  • increase in living material leads to increase in cell size and ultimately cells division of complex process in multicellular organisms
• Localization of Growth

  • Growth is restricted to certain embryonic regions called MERISTEMS
• Meristems

  • Where plant growth occurs
  • Site of repeated cell division unspecialised cells
  • Cells differentiate, and become specialised in relation to the function they will perform
• Basic Structures involve in Plant Growth and Development

  Embryo

  • Cotyledons, shoots and root apical meristems

  Meristems

  • Shoot
  • Axillary Root (Apical and Lateral)
  • Floral
  • Cambiums (cork, vascular)
• Types of Meristems 


  I. Apical

  • tips of roots and shoot
  • site of primary growth in plant

  II. Lateral

  • side portions, arising from cambium (base of nodes and stems)

  III. Intercalary

  • inserted between regions of differentiated tissues
• Types of Growth

  Indeterminate (Ricebean, winged bean)

  • apical meristems of the roots and stems remain permanently embryonic over long periods

  Determinate (corn, rice, mungbean)

  • other plant parts (leaves, flowers, fruits) are embryonic for limited period before the plant reaches maturity, have precise morphology and definite number of parts
• Internal Growth Mechanisms


  Correlation Effect

  • the regulatory effects exerted by one part of the plant on the growth or development in another part
• Internal Growth Mechanisms

  Organ Differentiation

  • As shoot increases in bulk, the size of the root system becomes proportionally larger
  • Reduction in vegetative growth when the plant is fruiting
  • Stimulation of fruit growth hormones produced in the developing seeds
  • Stimulating effects of buds/leaves on the rooting of stem cuttings