BIO 13- 1st LE- STRUCTURE, GROWTH, AND DEVELOPMENT

• The typical plant body has a: root system, shoot system, vegetative leaf body, and embryogenesis
• • Root system (typical plant body)
  • Usually underground, anchors the plant in the soil
  • For food storage
• • Shoot system (typical plant body)
  • Above ground, elevates plant above the soil
  • Photosynthesis, reproduction, dispersal food and water conduction.
• • Vegetative leaf body
  • Leaf- photosynthesis
  • Stem- support
  • Roots- absorption of water, anchorage, absorption of minerals and nutrients.
• • Growth (in embryogenesis)- permanent increase in size
  • Takes place in meristemszones where totipotent  cells rapidly divide.
• • Differentiation (in embryogenesis)- process by which cells undergo biochemical and structural changes to perform specialized functions
• • Morphogenesis (in embryogenesis)- development of form or shape of cells and organs.
• Features of Plant Growth: Primary and Secondary Growth
• • Primary growth
  • Responsible for length increase. In apical meristems in root and shoot tips
• Secondary growth

  • Responsible for increase in girth or diameter
• • Lateral meristems- cylindrical meristems at mature regions of roots and shoots.
  • Example: Vascular cambium, and Cork cambium or phellogen.
• Embryogenesis

  • Initiates plant development
  • Transports a single cell zygote into multicellular microscopic embryonic plants. 
  • A completed embryo has a basic body plan of a mature plant.
  • Establishes the basic plant body plan, and forms the meristems that generate additional organs in the adult.
• TWO IMPORTANT THINGS ESTABLISHED BY EMBRYOGENESIS. 

  1. Two basic development patterns
  2. Primary meristems- [shoot and root apical meristem]
• 1. Two basic development patterns (IMPORTANT THINGS ESTABLISHED BY EMBRYOGENESIS)
  2. Apical-basal axial pattern- established during the first cell division of the zygote.
  3. Radial pattern of tissues found in stems and roots- first visible at the globular stage.
• Division of the Zygote- Unequal division.
• Unequal division of the smaller apical cell- Undergoes subsequent cell division. Gives rise to most of the embryo proper.
• Unequal division of the Larger Basal Cell- Undergoes a limited series of divisions to form a suspensor.
• • Suspensor (larger basal cell)- attaches the embryo to the surrounding nutritive tissue and functions in the absorption and transport of various nutrients to the developing embryo
• Stages of Embryo Development: Globular Stage, Heart Stage, Torpedo Stage, and Maturation Stage.
• • Globular Stage (stage of development)-  globular embryo
  • Has a protoderm that gives rise to the epidermis.
• • Heart Stage (stage of development)- cotyledons emerges at the apical meristem, giving the embryo a heart shape. 
  • The embryo establishes a bilateral symmetry.
  • The transitional meristematic zones that will give rise to the future major tissue systems. 
  • Has transitional primary meristems; protoderm, ground meristem, pro-cambium
• Torpedo Stage- forms as a result of the cell elongation throughout the embryo axis and further development of the cotyledons
• Maturation Stage- embryo and seeds lose water, and become metabolically quiescent (inactive) as they enter dormancy.
• The mature dicot embryo is distinguished by the organization of the shoot and root apical meristems at either end of its short axis.