3. Plant Growth and Development

• Plant development is progressive and cumulative, influenced by plant regulators such as auxins, gibberellins, cytokinins, inhibitors, and ethylene
• Plant development has 3 aspects:

  • Growth: increase in cells/cell enlargement
  • Differentiation: transformation
  • Morphogenesis: 3-D shape/pattern
• There are 2 stages of plant development:

  • Fertilization to seed maturation
  • Seed germination to plant maturation
• Animal stages/phases of development include:

  • Pre-embryonic: gametogenesis
  • Embryonic: fertilization, cleavage, gastrulation, histological differentiation, organogenesis
  • Post-embryonic: maturation
• There are 2 types of plant growth:

  • Determinate/Close
  • Indeterminate/Open
• Development in flowering plants involves:

  A. Double fertilization to seed maturation:

  • Embryo (dicot, monocot)
  • Seed (dicot, monocot)

  B. Development from seed germination to maturation:

  • Primary growth
  • Development of the root
  • Development of the shoot
• Embryo consists of 2 cells:

  • Basal → suspensor
  • Terminal → embryo
• Dicot (C. bursa) has fruits with ovules containing developing and maturing embryos in 3 stages:

  • Globular
  • Heart-shaped
  • Torpedo/Y-shaped
• Globular embryo includes:

  • Endosperm
  • Integument
  • Suspensor
• Heart-shaped stage has 2 prominent mounds
• Torpedo-shaped stage includes:

  • Cotyledons
  • Epicotyl or plumule (embryonic shoot)
  • Plumule → shoot apex
  • Hypocotyl → radicle (embryonic root)
  • Seed coat/testa
• Monocot seed (Zea mays) consists of:

  • Endosperm: Aleurone, starchy layer
  • Embryo: Scutellum, Plumule, Coleoptile, Coleorhiza
• Dicot seed (Phaseolus sp.) outer part includes:

  • Seed coat, Hilum, Micropyle, Raphe
• Dicot seed (Phaseolus sp.) inner part includes:

  • Cotyledons, Plumule, Radicle
• Monocot seed (Z. mays) has endosperm in yellow color and embryo in a lighter color at the base
• Development of seed maturation involves:

  • Dormancy
  • Seed germination: imbibition, metabolic rate, assimilation and respiration, active cell division and growth, rupture of seed coat, sprouting of embryo
• There are 2 types of germination:

  • Epigeal
  • Hypogeal
• Primary growth includes the development of the root:

  • Z. mays root tip: Root cap, Quiescent center, Zonation (cell division/meristematic zone, cell elongation, cell maturation/differentiation)
• Meristematic zone consists of primary meristems:

  • Protoderm
  • Ground Meristem
  • Procambium
• Development of the shoot (Coleus sp. shoot apex) includes:

  • Apical meristem
  • Leaf primordia
  • Axillary buds
  • 3 zones: Zone of cell division, Zone of cell elongation, Zone of differentiation/maturation
• Apical meristem has tunica and corpus