Embryogenesis

• Embryogenesis – transformation of a single-celled zygote into a considerably more complex individual contained in the mature seed
• Embryogenesis is the transformation of single-celed zygote
• 3 main growths a plant undergo:

  • Morphogenesis
  • Organogenesis
  • Histogenesis
• Histogenesis - undifferentiated cells waiting for signal for differentiation
• Organogenesis - creation of different organs from tissues
• Morphogenesis - plants finalize shape formation
• Meristematic tissues are stem cells that has two 2 main: SAM and RAM
• Embryogenesis > Vegetative Dev. > Reproductive Dev.
• Vegetative Development reproduce photosynthetically active organ
• Reproductive Development - organs that can reproduce
• Seed Phase: Dormancy and Germination
• Dormancy - capability of a plant to be inactive utilizing its nutrient; cant be intrinsically, extrinsically, or mechano
• Naturally inducing effect of dormancy are:

  • is the soil nutritious?
  • air suitable?
  • water resources
• Germination - the differentiation of cells; especially creation of shoot and fruit
• Secondary growth as early as 8 stage occurs
• 3 main reason why Arabidopsis is used as model organism:

  • small genome size
  • small size cultivated in laboratory setting
  • rapid life cycle
• 2 axis:

  • Apical-Basal axis - primary growth
  • Radial axis - secondary growth
• In the first division, the apical cell gives rise to SAM, while the basal cell creates roots and the connection of the embryo to the mother seed is formed giving nutrient to apical cell.
• protoderm gave rise to ectoderm of plant
• hyphophysis creates the RAM while suspensor cells are the derivatives of basal cells
• Heart form is due to the rise of cotyledon because of auxin
• Later on the seed established the shoot apical and root apical
• In mature seed, the embryo is the only one bending
• In 8th cell stage is the start of secondary growth
• Small proteins appear to move readily in all stages of embryogenesis (B, H, N), but the mobility of larger proteins is lower and becomes more restricted in older embryos.
• Plasmolemma - gated channel which helps in communication between cells of plant
• The older the plant embryo, the smaller and more discreet the size of plasmolemma
• Gnom genes control apical-basal polarity
• Monopteros genes control formation of primary root
• Gurke creation of apical part; cucumber in French
• Fackel responsible for central region; torch in German
• Monopteros responsible for basal part; one pair of wings
• Gnom responsible for terminal ends; shrinking of cell plants
• Auxin or indole-3-acetic acid that regulates cell divison and growth
• Seed has no regulatory center when auxin is absent;
• Procambial precursors for the vascular stele lie at the center of the radial axis
• Wooden Leg (WOL) gene is required for normal phloem development.
• Differentiation of cortical and endodermal cells involves the intercellular movement of transcription factor
• Mutants with reduced SCR or SHR fail to undergo a round of cell division that produces the cell layers for both cortex and endodermi
• scarecrow (scr) gene responsible for asymmetric division of cortex/endodermis; and maintenance of quiescent center