Plants

• Basic Principles:

  • Photosynthesis requires: light, CO2, H2O
  • Growth requires: N, P, K, Mg, and other nutrients
  • Plant structure is dynamic
  • Indeterminate growth: continues to grow with the right conditions
  • Phenotypic plasticity: influenced by their environment
• Shoot system:

  • Mostly above ground
  • Role: to absorb sunlight, gas exchange, reproduction
• Root system:

  • Below ground
  • Role: anchor plant, absorb H2O and nutrients, store energy, symbiotic relationships (fungi, bacteria)
• Roots:

  • Tap root --) eudicot plants
  • Fibrous roots --) monocot plants
  • Phenotypic plasticity --) grow deeper in drier soil
  • Longer roots --) plant is more likely to continue growing in a drought
• Modified roots:

  • Anchor roots
  • Prop roots
  • Pheumatophores
  • Storage roots
• Anchor roots:

  • Function: stem to walls and other plants
  • Example: ivy
• Prop roots:

  • Function: stabilize the stem
  • Example: corn
• Pneumatophores:

  • Function: allows gas exchange by emerging out of water
  • Example: Mangrove tree
• Storage roots:

  • Function: store carbohydrates and other nutrients for future use
  • Example: Sugar beet
• Shoots/Stems:

  • Grow taller to access light
  • Dry + windy environment --) shorter plant
  • Modified shoots/stems:
  • Water-storage structures
  • Stolons
  • Rhizomes
  • Tubers
  • Thorns
• Water-storage structures (shoots/stems):

  • Function: stems store water in dry environments
  • Example: cactus
• Stolons:

  • Functions:
  • Horizontal runner (growth)
  • Adventitious roots + leaves
  • Produces new individuals at nodes above ground
  • Example: strawberry plant
• Rhizomes:

  • Functions:
  • Horizontal stems
  • Asexual reproduction
  • Produces new individuals at nodes belowground
  • Stores carbohydrates
• Tubers:

  • Functions:
  • Underground stem
  • Store carbohydrates
  • Example: potatoes
• Thorns:

  • Function: provide protection from herbivores
• Simple leaf: petiole and single blade
• Compound leaf: blade is divided into leaflets
• Double compound leaf: large, but rarely damaged by wind or rain
• Needle-like leaf: characteristic of species adapted to cold or hot, minimizes water loss by transpiration and wind
• Larger surface area of leaf maximizes light capture
• Smaller surface area of leaf minimizes water loss
• Modified Leaves:

  • Bulbs
  • Suculent leaves
  • Tendrils
  • Floral mimics
  • Traps
• Bulbs:

  • Functions:
  • Stores food
  • Underground (no light --) no chlorophyll)
  • Example: onions
• Succulent leaves:

  • Function: stores water
  • Example: aloe vera
• Tendrils:

  • Function: aids in climbing/movement
  • Example: pea tendrils
• Floral mimics:

  • Function: attracts pollinators
  • Example: red poinsettia
• Traps:

  • Functions:
  • Hood discourages bugs from flying out
  • Digestive enzymes/bacteria digest
  • Example: pitcher plant
• Cellulose:

  • Most abundant compound on Earth
  • Humans can't digest it (we don't have the enzyme for it)
  • Some animals have symbiotic relationships with microbes that can digest cellulose
• Amylase breaks 1-4 glycosidic bonds, but it can't break down cellulose
• The Plant Cell Componants:

  • Middle lamella
  • Primary wall
  • Secondary wall
  • Simple pits
  • Plasmodesmata
• Middle lamella: pectin glues cells together to form tissues and organs
• Primary wall:

  • Create first
  • Made of cellulose
  • Resists internal pressure
  • Allows plants to stay upright
  • Prevents cells from lysing
• Secondary wall:

  • Only in specialized cells (xylem)
  • Thick and made of cellulose and lignin (cross-linked polyphenols)
  • Provides strength
  • Important for water transport
• Simple Pits:

  • Thin areas of secondary wall that connects adjacent cells
  • Allows movement of fluids between cells
• Plasmodesmata:

  • Smaller channels in cell wall
  • Allows movement of small molecules
• Plastids:

  • Chloroplasts
  • Amyloplasts
  • Chromoplasts
• Chloroplasts: photosynthesis and gas exchange
• Amyloplasts: roots and carbohydrate storage
• Chromoplasts: attracts pollinators, in fruits and flowers
• Tissue Systems:

  • Simple tissues: single cell type
  • Complex tissues: > 1 cell type