Plant Development

• Seed plants

  Classified into two major groups: gymnosperms and angiosperms
• Gymnosperms


  • Can be both male and female
  • Means "naked seeds", based on the unenclosed condition of the seeds
  • Examples: conifers, cycads, Ginkgo, gnetophytes
• Angiosperms


  • A plant that has flowers and produces seeds enclosed within a carpel
  • Large group that includes herbaceous plants, shrubs, grasses, most trees
• Seed structure


  Acts as the primary basis of angiosperm division/classification
• Monocotyledon


  • The seed is surrounded with a protective seed coat
  • Aleurone layer lies under the seed coat and functions as a kind of digestive organ in seed germination
  • Endosperm is a food storage tissue
  • Discards the primary parts after they have served their function, leaving behind only the radicle, the mesocotyl, and the shoot apex
  • Means "single leaf", referring to the single cotyledon that appears to be homologous with a leaf
  • Scutellum is a very large cotyledon that develops in grass embryos
• Dicotyledon


  • Have two cotyledons that function as actual leaves or as food storage organs
  • Plumule corresponds to the shoot apex in monocots
  • Undergoes a distinct fertilization process that produces an embryo from a zygote
  • Hypocotyl is the part of the axis below the point of attachment of the cotyledons
  • Epicotyl is the part of the axis above the point of attachment of the cotyledons
• Seed germination


  The embryonic plant is kept in a state of suspended development called dormancy which ends when germination takes place
• Breaking dormancy


  1. The embryo emits a hormone called gibberellin which diffuses through the seed

  2. In monocots, the hormone then triggers the production of digestive enzymes by the aleurone

  3. In dicots, the digestive enzymes are produced by the cotyledons

  4. Produced enzymes then proceed to break down the stored food in the endosperm of cotyledons
• Early Root and Emergence

  • Microscopic examination will disclose a cap consisting partly of dead or moribund cells at its apex
• Primary meristems


  • Give rise to differentiated tissues such as the phloem and the xylem
  • Some tissues derived remain undifferentiated and form cambium layers of the stem and the similar pericycle layer of the root
• Leaf growth


  1. Each leaf originates on the side of the meristem, growing upward as it enlarges and begins to differentiate

  2. Another group of cells next to it and somewhat above it begins to grow outward and upward
• Leaf fall


  Leaves age and die in all plants
• Abscission


  • The process by which plants shed one of their parts
• Secondary growth in dicots

  A process of differentiation must occur behind the growing tips of the stem and the root
• Secondary growth usually does not occur in monocots
• Monocot secondary growth


  • The trunk of a tree-like monocot such as bamboo or a palm tree remains roughly the same diameter from base to crown
  • Primary thickening meristem immediately behind the apical meristem lays down vascular and other differentiated tissues to form the stem of the palm tree
• Aleurone Layer

  • lies under the seed coat
  • Function: digestive organ in seed germination
• Provascular cylinder


  cylinder in the center or the apical bud that develops into the vascular tissues
• how do cork cambium age?

  they die and converted to cork
• (3) Early Root and Emergence

  1. Zone of Division
  2. Zone of Elongation
  3. Zone of Maturation
• Zone of Division 


  actual living tissue undergoes mitosis
• Zone of Elongation

  responsible for most of the lengthwise growth of the root tip
• Zone of Maturation 


  where tissue differentiation begins