121 LAB - FIRST EXAM

• Seed dormancy


  A period of inactivity or extremely low metabolic activity in mature seeds, which may last for months, years or even centuries
• Germination


  The process where the embryo within a mature seed resumes growth upon return to favorable conditions, becoming a young seedling
• Seed coat


  • Can inhibit germination through: 1) Embryo unable to break through 2) Contains chemical inhibitors 3) Prevents access to water and oxygen
• Environmental requirements for germination

  Light, proper temperature, presence of oxygen, presence of water
• Small-seeded species usually require light as a germination cue to ensure seeds only germinate at or near the soil surface</b>
• Some species require a prolonged cold period prior to germination to break down a chemical germination inhibitor
• Plants growing in hot climates may have seeds that need a hot period in order to germinate, to avoid germination in hot, dry summers
• Imbibition

  The initial uptake of water that starts the germination process
• Mechanism of germination

  1. Imbibition

  2. Enzyme activation to break down starch

  3. Radicle swelling

  4. Hypocotyl/epicotyl elongation

  5. Cotyledon extension
• Epigeous germination


  Hypocotyl elongates, cotyledons extend above ground
• Hypogeous germination


  Epicotyl elongates, cotyledons remain belowground
• Seed parts

  • Seed coat
  • Seed leaves/cotyledons
  • Embryo/baby plant
• Conditions necessary for seed germination

  • Air
  • Water
  • Warmth
• Stages of seed germination

  1. Seed absorbs water

  2. Root sprouts and grows downward

  3. Shoot sprouts and grows upward

  4. Seedling develops green leaves and makes own food

  5. Cotyledons dry up and fall off
• Water in plants


  Comprises 80-90% of plant's total weight, used to support cell structure, metabolic functions, nutrient transport, and photosynthesis
• Organic compounds


  Chemical compounds containing carbon, such as carbon dioxide from the atmosphere
• Inorganic compounds


  Compounds that do not contain carbon, such as nitrogen and potassium
• Fresh weight


  Weight recorded immediately after harvest, includes water content
• Dry weight


  Weight recorded after drying plant tissue, eliminates water content
• Ash


  Mineral component of a dried plant sample that remains after burning off organic matter
• Dry matter


  True dried component of a plant sample, excluding any residual moisture
• Photosynthesis converts carbon dioxide and water into oxygen and glucose
• Dry Matter Percentage


  Divide dry weight by fresh weight and multiply by 100
• Ash Percentage


  Divide ash weight by fresh weight and multiply by 100
• Organic Matter Percentage


  Subtract ash weight from dry weight, divide by fresh weight, and multiply by 100
• Different temperature treatments

  • Can have varied effects on seed germination depending on the species and their temperature requirements
  • Optimal temperatures promote enzymatic activity and metabolic processes necessary for germination, resulting in higher germination rates and healthy seedling growth
  • Low temperatures may inhibit germination or delay it due to slower metabolic rates
  • High temperatures can denature enzymes and damage cellular structures, leading to reduced germination rates or abnormal seedling development
• Photosynthesis


  1. Converts carbon dioxide and water into oxygen and glucose

  2. Glucose is used as food by the plant

  3. Oxygen is a by-product
• Cellular Respiration


  Converts oxygen and glucose into water and carbon dioxide
• Photosynthesis and cellular respiration


  • Are connected through an important relationship
  • The products of one process are the reactants of the other
• The equation for cellular respiration is the direct opposite of photosynthesis
• • Photosynthesis makes the glucose that is used in cellular respiration to make ATP
  • The glucose is then turned back into carbon dioxide, which is used in photosynthesis
  • While water is broken down to form oxygen during photosynthesis, in cellular respiration oxygen is combined with hydrogen to form water
  • While photosynthesis requires carbon dioxide and releases oxygen, cellular respiration requires oxygen and releases carbon dioxide
  • The released oxygen is used by us and most other organisms for cellular respiration
• • Cellular respiration works best in the presence of oxygen
  • Without oxygen, much less ATP would be produced
• The exchange of carbon dioxide and oxygen through photosynthesis or cellular respiration worldwide helps to keep atmospheric oxygen and carbon dioxide at stable levels
• Most life on Earth is possible because the sun provides a continuous supply of energy to ecosystems
• Photosynthesis


  The process in which light energy is converted to chemical energy in the form of sugars
• Photosynthesis


  • In a process driven by light energy, glucose molecules (or other sugars) are constructed from water and carbon dioxide, and oxygen is released as a byproduct
  • The glucose molecules provide organisms with energy and fixed—organic—carbon
• Leaves are the sites of photosynthesis in most plants
• Chloroplasts


  • Specialized organelles in leaf cells that carry out the reactions of photosynthesis
  • Contain disc-like structures called thylakoids arranged in piles like stacks of pancakes that are known as grana
  • The membrane of each thylakoid contains green-colored pigments called chlorophylls that absorb light
• Photosynthesis


  1. Light-dependent reactions

  2. Calvin cycle
• • The light-dependent reactions capture light energy and store it temporarily in the chemical forms of ATP and NADPH
  • The Calvin cycle uses ATP and NADPH to fix carbon dioxide and produce three-carbon sugars