Plant organs and transport and support system in plant

• Five organs of the Plant

  • Roots
  • Stem
  • Leaves
  • Flowers
  • Fruits
• Roots

  • Absorb water and minerals and act as anchors for plants
• Stem

  • Supports leaves and fruits, Transports substances from the roots to the tips of leaves
• Leaves


  • Photosynthesis
• Flowers


  • For reproduction, Have the male and female parts
• Fruits


  • They have the seeds
• Adaptations of the leaf

  • Large surface area, maximum absorption for sunlight
  • Xylem brings water to the leaf for photosynthesis
  • Phloem transports manufactured food
• Photosynthesis: large surface area, maximum absorption for sunlight
• Xylem


  • Brings water to the leaf for photosynthesis
• Phloem


  • Transports manufactured food
• Transparent cuticle and epidermis allows light into the leaf
• Stomata regulates O2, CO2 and H2O vapour
• Gaseous exchange

  • Large surface area, increased diffusion
  • Thin epidermis, allows for rapid diffusion
  • Palisade cells are closely packed, prevents excess loss of gases
  • Stomata allows for quick diffusion of gases (O2, CO2 and H2O vapour)
• Thick cuticle

  • Prevents excess gaseous exchange
• Guard cells

  • Control opening and closing of stomata
• Transpiration

  • Thick cuticle prevents water loss
  • Thin leaf allows for quick diffusion
  • Large surface area allows for quick diffusion
  • Intercellular spaces allow movement of water vapour from cells
• Transport system

  • Xylem transports water from the roots to the leaf
• Movement of substances in a leaf

  1. Carbon dioxide enters the leaf from the atmosphere through the stomata during the day, moves through intercellular spaces by diffusion

  2. Water enters the leaf by xylem in vascular bundles (Osmosis), leaves the plant during transpiration as water vapour

  3. Oxygen is given off during photosynthesis, leaves the leaf by diffusion from intercellular spaces through stomata into atmosphere

  4. Glucose made during photosynthesis in palisade cells, dissolved in water, transported in phloem to other parts of the plant
• Only green parts of plants can photosynthesize
• Functions of Roots


  • Absorption of water and nutrients
  • Anchorage of the plant
  • Support
  • Storage of food and nutrients
  • Transport
  • Reproduction
• Types of Root Systems

  • Tap roots found in Dicotyledons
  • Fibrous or adventitious roots found in Monocotyledons
• Guard cells control the opening and closing of stomata based on environmental conditions such as light intensity, humidity, and temperature.
• Stomata are small openings on the underside of leaves, surrounded by guard cells that regulate gas exchange between the leaf and atmosphere.
• Cortex


  Thin walled parenchyma cells that provide support when turgid
• Turgid


  When a cell has a vacuole full of water and provides support against cell wall
• Collenchyma cells


  Cells with thickened corners that provide support
• Vascular bundles


  Arranged in a ring, with cambium separating the xylem and phloem, surrounded by sclerenchyma tissues that provide support
• Pith


  Central pith made of parenchyma cells, where starch is stored
• Secondary thickening


  1. Increase in thickness of stems and roots in dicotyledonous plants as they grow older

  2. Vascular cambium forms complete rings in stems

  3. New xylem produced towards inside, new phloem towards outside

  4. New rings of secondary xylem and phloem produced each year by cambium

  5. New xylem closest to cambium transports water and minerals up stem, older xylem filled with waste products near centre

  6. Cambium and phloem pushed out to form narrow inner bark, outer bark produced by cortex
• Herbaceous stems


  • Usually soft but strengthened by secondary thickening
  • Mature stems resemble young woody plants
• Difference between woody and herbaceous dicotyledons


  Activity of vascular cambium - in woody stems it is highly active and produces large amounts of secondary tissue, in herbaceous stems it is less active and produces less wood
• Annual rings


  • Concentric rings in stems of woody dicotyledonous plants, found in secondary xylem
  • Form due to cambium having different rates of development during the year
  • Spring wood is light in colour with large, thin walled vessels
  • Autumn wood is dark in colour with smaller diameter, thicker walled vessels
• Annual rings help determine age of plant and provide information about environmental conditions during each year
• Transpiration


  Loss of water in the form of water vapour by evaporation from leaves of plants
• Transpiration pull


  The force that pulls water up the plant from the roots, as water moves into leaf cells to replace that lost by transpiration
• Wilting


  Non-woody parts of plant become limp and droop due to water loss
• Guttation


  Appearance of drops of xylem sap on leaf edges due to root pressure when water absorption exceeds transpiration loss
• Plant growth forms


  • Herbs
  • Shrubs
  • Vines
  • Trees
• Annuals have a life cycle that lasts one year, biennials two years, perennials many years
• Secondary thickening in plant stems

  1. Procambium in vascular bundles forms vascular cambium

  2. Interfascicular cambium forms between xylem and phloem

  3. Vascular cambium forms complete ring

  4. Secondary xylem and phloem produced by division of cambium ring

  5. Annual rings form in secondary xylem