kei

• Plant transport


  Transport of food, water, and minerals through the shoot system
• Plant transport systems

  • Shoot system
  • Root system
• Materials need to be transported between the root and shoot system
• Xylem


  Transports water and minerals, upward one-way movement, consists of tracheary elements like tracheids and vessel members
• Vessel elements


  • Wide, thin-walled, and hollow cells, dead at maturity, transport and support
• Tracheids


  • Narrower, tapered cells, have pits at the end to allow water transport
• Water is still collected by the roots at night when transpiration is not occurring as much
• Transpiration


  Plants take up liquid water from the soil and release water vapor into the air from their leaves
• As water flows in

  Pressure is generated which forces the fluid to go up the xylem
• Root pressure


  A force that helps to drive fluids upward into the xylem, buildup of water pressure in the roots
• Root pressure can result in guttation, which means exuding water from margins of the leaf, not through stomata
• Plasmolyze - too much water evaporates from the plant
• Capillary action


  Tendency of a liquid to move up against gravity when confined within a capillary (a narrow tube)
• Properties of water


  • Surface tension
  • Adhesion
  • Cohesion
• Cohesion-tension hypothesis


  Widely accepted model for movement of water, caused by combination of processes like capillary action and transpiration
• Phloem


  Transports sugar and other items, direction of movement is either upwards or downwards (bi-directional), found in shoot system next to xylem, composed of sieve tubes with companion cells and various support cells
• Sieve tube elements


  • Alive at maturity, long narrow with sieve plates at ends, no nucleus, ribosomes and vacuole

  
• Companion cells


  • Attached to the side of the sieve-tube element, organelles serve both cells, does not transport
• Sugar source


  An organ where sugar is being produced, usually leaves
• Sugar sink


  An organ that consumes or stores sugar, usually roots, growing stems, buds, and fruits
• Pressure is created at source as sugar is produced


  Pressure decreases in sink as sugar is used
• Water diffuses into phloem from xylem


  Due to decreased water potential, pushes the sugar from source to sink
• Sugar sink can become a sugar source in the middle of a growing season, and leaves and stems are considered the sugar source as they are actively photosynthesizing
• Pressure flow model


  High concentration of sugar at the source and low solute potential will attract water from the xylem, creating high pressure potential or high turgor pressure in the phloem, which forces the movement of the phloem sap containing sugar from the source to the sink through bulk flow
• Bulk flow


  Movement of a mass of fluid due to the presence of a pressure gradient
• Sugar is rapidly removed from the phloem at the sink


  Increases solute potential, water is forced to move from phloem back to xylem, pressure potential goes down
• The vascular tissue is arranged into bundles of xylem and phloem that are scattered throughout the ground tissue
• Monocot


  Scattered vascular bundles
• Dicot


  Vascular bundles arranged in a ring-like fashion
• Plant nutrients


  • Macronutrients from air and water: Carbon, Hydrogen, Oxygen
  • Macronutrients from soil: Nitrogen, Phosphorus, Potassium, Calcium, Magnesium, Sodium
  • Micronutrients from soil: Boron, Chloride, Copper, Iron, Manganese, Molybdenum, Nickel, Zinc
• Nitrogen


  Affects leaf growth and development for healthy green foliage
• Phosphorus


  Improves the roots, stems, flowers, and fruits
• Potassium


  Promotes photosynthesis and improves plant resistance
• Plant hormones (phytohormones)


  Organic substances that regulate plant growth and development, needed to regulate signal networks of plants, increase defense against pathogens and adapt to environmental stress
• Growth promoters


  • Auxin
  • Cytokinin
  • Gibberellins
  • Salicylic acid
• Growth inhibitors


  • Abscisic acid
  • Brassinosteroids
  • Ethylene
  • Jasmonic acid
• Asexual reproduction


  Produces individuals that are genetically identical to the parent plant, without the involvement of gametes or fertilization
• Advantages of asexual reproduction

  • Increased rate of maturity
  • Sturdier adult plant
  • Can take place naturally or artificially
  • Quicker and more efficient than sexual reproduction
• Disadvantages of asexual reproduction

  • Lack of genetic diversity
  • Accumulation of mutations
• Types of asexual reproduction

  • Vegetative propagation
  • Apomixis