PLANT BIO LONG Q

• Plants are among the most successful organisms on the planet. Their success can be attributed to various biological adaptations that let them thrive many habitats.
• Ability of plants to alter between reproduction and development


  Allowed them to colonize environments with diverse conditions
• Plants have also evolved various reproductive structures to allow them to increase their chances of successful fertilization and development.
• Plants


  • Multicellular organisms
  • Photosynthetic capacity
  • Cellulosic cell wall
  • Plastids in cytoplasm
  • Life cycle with alternation of generations

  
• Major plant groups


  • Non-Vascular Plants (Hornworts, Liverworts, Mosses)
  • Vascular Plants (Pteridophytes, Spermatophytes (Gymnosperms, Angiosperms))
• Bryophytes


  Spore-bearing non-vascular plants
• Pteridophytes


  Spore-bearing vascular plants
• Spermatophytes


  Seed-bearing vascular plants
• Alternation of generations


  Common life cycle pattern for green plants, with alternation of haploid and diploid phases
• Floral anatomy


  • Pistil (stigma, style, ovary)
  • Stamen (anther, filament)
  • Petals
  • Sepals
  • Receptacle
  • Pedicel

  
• Angiosperm life cycle


  1. Seeds contain developing embryos (first sporophyte stage)

  2. Embryos undergo development and differentiation to become seedlings

  3. Continuous growth and development allows seedling to reach maturity

  4. Adult stage becomes sexually mature

  5. Adults produce gametophytes in pollens and ovules

  6. Fusion of gametes occurs during pollination

  7. Ovary develops into fruit, ovules become seeds
• Gymnosperm life cycle


  1. Female cones

  2. Male cones
• Fern life cycle


  1. Spores at underside of fertile fronds (sporophyte) develop into gametophytes

  2. Gametophyte produces eggs and sperms

  3. Fertilization forms diploid zygote that develops into young sporophyte

  
• Comparison of reproductive structures and processes

  • Angiosperms: Floral structures, seeds, pollination, fruit formation, dominant sporophyte
  • Gymnosperms: Cones, seeds, pollination, fruit formation, dominant sporophyte
  • Pteridophytes and Bryophytes: No floral structures, spores, no pollination, no fruit, some sporophyte and some gametophyte dominant

  
• Forms of reproduction in angiosperms

  • Asexual reproduction (requires single parent, no gamete fusion, genetically identical offspring)
  • Sexual reproduction (requires fusion of sperm and egg, enhances genetic variation)
• Apomixis


  Allows production of embryos from unfertilized eggs in ovules
• Vegetative propagation


  Allows plant parts to produce buds that can develop into new individuals
• Pollen grains


  Contain male gametophytes in angiosperms, with two sperm nuclei and a tube nucleus
• Ovules


  Contain the egg nucleus and polar nuclei that will be fertilized
• Double fertilization


  One sperm nucleus fertilizes egg nucleus, other fertilizes polar nuclei, producing diploid embryo and triploid endosperm
• Plant development


  • Shoot apical meristem allows continuous upward growth
  • Cambium allows further growth of stems and roots by increasing thickness
  • Root apical meristem allows continuous downward growth of roots
• Embryogenesis


  Ovary wall differentiates into exocarp, mesocarp, and endocarp in different fruit types
• Organogenesis


  Plumule, hypocotyl, cotyledons, radicle, and epicotyl develop during seedling growth

  
• The life cycle of plants is characterized by alternation of generations between diploid sporophyte and haploid gametophyte stages.

  
• In a generalized angiosperm life cycle, a plant starts as a seed, develops into a seedling, reaches maturity, produces flowers for fertilization, and forms fruits containing new seeds.

  
• Fertilization happens when pollen penetrates the ovary of the flower, and the fertilized ovule develops into a fruit containing seeds for dispersal.
• Embryogenesis and organogenesis are important processes that take place after seed formation, leading to the formation of functional plant organs.
• The general pattern of the plant life cycle involves reproductive and developmental phases alternating between generations.