BIOLOGY midterm

• Stems


  • Support the leaves
  • Function in transporting materials
  • Function in providing storage
• Types of Stems

  • Stolon (Runners): horizontal stems that grow along the soil's surface (ex: Strawberry)
  • Rhizomes: Underground horizontal stems, food storage (ex: Iris flower)
  • Tuber: a swollen, underground stem, food storage (ex: Potato)
  • Fleshy – green stems: water storage, Photosynthesis (ex: Cactus)
  • Bulb: shortened compressed stem surrounded by fleshy leaves
  • Corm: stem tissues with scaly leaves on top
• Monocot stem


  The vascular bundles are scattered
• Dicot stem


  Have one ring or concentric rings of vascular bundles
• Growth Of The Stem


  1. Cells produced by the apical meristem result in an increase in the length of the stem

  2. Plant grows taller, increase in stem diameter provides additional support

  3. The production of xylem and phloem throughout the year can produce annual rings (circles that look like rings)
• Heart wood


  The darker wood in the center of a tree
• Sap wood


  The lighter – colored wood near the outside of the trunk
• Bark


  The protective outside covering of woody plants, made of dead cork cells, cork cambium, phloem
• Node


  Each leaf is attached to the stem at a location called the node
• Internode


  The space between nodes
• Petiole


  Attaches leaf to stem
• Bud


  It grows into a new shoot system (above ground part of a plant, consisting of stems and leaves), enclosed by bud scales
• Types of Buds


  • Terminal bud
  • Lateral bud (Axillary bud)
• Translocation


  Movement of sugars from source to sink through the plant
• Source


  Leaves, sometimes stems
• Sink


  Stems, roots, flowers, and fruits
• Cohesion


  The strong attraction of water molecules to each other
• Tension


  The strong attraction of water molecules to the xylem walls
• As water is pulled up the xylem, more water enters the roots from the soil
• Simple leaf


  Single blade, Venation: Palmate (network venation), Arrangement: Opposite
• Compound leaf


  The blade is divided into leaflet, Venation: Pinnate or Parallel, Arrangement: Alternate or Whorled
• Cuticle


  A thin waxy layer covering the two outer layers of cells (upper epidermis and lower epidermis), reduces water loss by evaporation and acts as a barrier to invading microorganisms
• Stomata


  Pores in the lower epidermis that allow carbon dioxide to diffuse into the leaf and allow oxygen and water vapor to diffuse out
• Guard cells


  Regulate gas and water exchange
• Transpiration


  Water loss from the plant through the stomata
• Palisade mesophyll


  Below the upper epidermis, made of elongated cells each containing hundreds of chloroplasts, main site of photosynthesis
• Spongy mesophyll


  Found below the palisade mesophyll, made of rounded, loosely packed cells having fewer chloroplasts than the palisade mesophyll, air spaces between the cells forming the main gas exchange surface of the leaf
• Xylem


  The water – carrying vascular tissue (with minerals and nutrients)
• Phloem


  The food – carrying vascular tissue (sugar, inorganic compounds)
• Monocot leaf


  Shows parallel venation
• Dicot leaf


  Shows palmate (net) venation
• Photosynthesis


  The process of using light energy, carbon dioxide, and water to produce sugar (glucose) and oxygen
• Leaf Modifications


  • Succulents (ex: Cacti) have modified leaves called spines, which reduce water loss and protect the plant
  • Poinsettias have leaves called bracts that change color to attract pollinators
  • Sundew plant have leaves that produce sticky substances to trap insects
  • Pitcher plant have cylinder-like modified leaves that fill with water to trap and drown insects and animals
  • Leaves that contain toxic chemicals to deter organisms from touching them (ex: poison ivy, poison oak)
  • Leaves that deter herbivores from eating them (ex: tomato and squash leaves have tiny hairs with glands called trichomes that contain substances to repel insects and other herbivores)
  • A bulb's leaves are food storage structures