Gen Bio 2

• Main parts of a plant: roots, leaves, stem, flower
• shoot system - above the ground system (stems and leaves)
• root system - underground system (roots)
• responsible for the transport in plants

  *Xylem

  *Phloem
• xylem is responsible for water transportation from root to shoot
• xylem transport water and minerals in an upward direction from the roots to the leaves
• xylem consists of vessel elements, tracheids, and parenchyma cells
• Vessel element - wide, thin wallowed, hollow cells; dead at maturity
• Tracheids - narrower, tapered cells, thinner; have pits at ends which allow water transport
• Water is still "collected" by the roots at night, when transpiration is not occurring as much
• root pressure - upward push of xylem sap
• guttation - exuding water from leaf margin, not through stomata
• Osmosis - movement of water through the roots
• Cappilary action - tendency of a liquid to move up against gravity when confined within a capillary (a narrow tube).
• 3 properties of water:

  1. Surface tension
  2. Adhesion
  3. Cohesion
• Cohesion tension hypothesis - pulls water up the xylem
• Phloem -  transports sugars made by the leaves and other items to the rest of the plant (bidirectional)
• Components of phloem:

  1. Sieve-tube elements
  2. Companion cells
• Sieve tube elements - maintain cells and transport necessary molecules with the help of companion cells
• Sugar source - an organ where sugar is being produced usually in leaves
• Sugar sink - consumes or stores sugar usually in roots, growing stems, buds, and fruits
• Pressure is created at source as sugar is produced
• Pressure decreases in sink as sugar is used
• vascular tissue -  is arranged into bundles of xylem and phloem that are scattered throughout the ground tissue.
• dicot - arranged in a ring-like fashion
• monocot - scattered bundles
• Macronutrients from air and water: carbon, hydrogen, oxygen
• Macronutrients from soil: nitrogen, phosporus, potassium, calcium, magnesium, sodium
• Micronutrients: boron, chloride, copper, iron, manganese, molybdenum, nickel, zinc
• Nitrogen - affects leaf growth and growth 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
• Growth promoters:

  1. Auxin
  2. Cytokinin (CK)
  3. Gibberellins (GA)
  4. Salicylic acid (SA)
• Growth inhibitors:

  1. Abscisic acid (ABA)
  2. Brassinosteroids (BR)
  3. Ethylene (ET)
  4. Jasmonic acid (JA)
• • Auxin promotes cell growth and elongation of the plant
• • Cytokinin (CK) - promotes seed development, cell expansion, cell differentiation, and N assimilation
• Gibberellins (GA) stimulate cell elongation and response to nutritional limitation
• Salicylic acid (SA) - defense against a variety of biotic and abiotic stresses; inhibits seed germination
• • Abscisic acid (ABA) - regulates plant growth, development, and stress responses