BOT3015 Test 02 Study Guide Lecture 11 Plastids all cells have them specialized organelles within plant cell Proplastid present in meristems early stage of plastid Chloroplasts photosynthesis Granum stacks of thylakoid membrane surrounded by stroma Amyloplasts starch storage amyloplast is response in gravitropic response Chromoplasts storage of carotenoid pigments Etioplast plastid in the dark Cell wall structural support for plant cells Primary permit cell growth in growing plants cellulose semicellulose pectin usually thin no lignin Secondary second layer after plant growth has ceased limit cell growth usually thick have lignin EX cotton fibers secondary xylem hemp Cellulose microfibrils found in cell walls give support strength stiffness to primary cell wall Matrix shot chain polysaccharides contributing to the cell wall Lignin made of phenolic compounds forms a stiff glue surrounding the cellulose microfibrils Central vacuole generates turgor pressure within the cell contains solution of potassium salts used to create concentration gradients for water movement membrane bound high osmotic Osmotic driven H2O uptake turgor pressure cell growth Plasmodesmata cytoplasmic connections between neighboring plant cells permit movement of small molecules MW 800 can diffuse communication exchange Vacuoles in meristem cells are small Lecture 12 Photosynthesis Light H2O CO2 O2 C3H6O3 NADPH occurs in the grana 1 Light reaction light energy is converted into chemical energy in the form of ATP and 2 Dark Reaction Calvin Cycle CO2 is converted to sugar using the chemical energy from the light reactions occurs in the stroma Antenna complex located at the periphery capture photons chlorophyll b carotenoids and chlorophyll are main absorbers of light pass energy to reaction center Reaction center located at the center splits H2O into H and O2 Photosystem II 680 nm splits H2O Photosystem I 700nm collects electrons from PSII ATP is formed as a result of the formation of a proton gradient and ATPase complex Rubisco carries out CO2 fixation 5 carbonRuBP sugar into two 3 carbon sugars PGA Has dual activity carboxylase and oxygenase oxygenase is unwanted Photorespiration when CO2 is low Rubisco binds to O2 and breaks down RuBP to glycolate and then eventually to CO2 reduces photosynthetic activity by 30 40 C3 plants fix CO2 normally into 3 carbon compound suffer under high temperature conditions C4 plants fix CO2 into a 4 carbon compound called malate CAM plants modification in C4 plants temporal separation of CO2 fixation between day and night save H2O and grow in hot dry areas Lecture 13 Plant nutrition involves the uptake from the environment of raw materials required for growth Essential Elements C H O MG P N S Iron deficiency chlorosis in leaves Macronutrients 9 C H O N P K Ca Micronutrients 8 Uptake Nutrients come from both the soil and air carbon Most minerals in the soil are negatively charged Nitrogen in the soil is found mostly in the form of nitrate Most mineral water enter through active transport in youngest parts of roots root hairs increase surface area Apoplastic diffusion through cell walls Symplastic uptake in the cytoplasm of cell Transcellular movement of nutrients through plasmodesmata in cytoplasm Casparian strip band of hydrophobic material forcing water to go through the cells Endodermis allows plants to maintain mineral ion concentrations in the xylem Rhizobium nitrogen fixing bacterium forms symbiotic relationship Mycorrhizae mutualistic fungi in roots of plants critical for phosphate uptake can increase root surface area Nitrogen Cycle 1 Nitrogen fixation N2 NH4 energy requiring reaction anaerobic process nitrogenase catalyzes fixation of nitrogen inhibited by oxygen 2 Nitrification NH4 NO3 carried out only by bacteria energy yielding reactions 3 Ammonification organic compounds NH4 4 Denitrification NH4 N2 Carbon cycle CO2 used from atmosphere Replaced by combustion and animal respiration Phosphate is not recyclable Lecture 14 Sugar and amino acids to non photosynthetic organs Water and minerals to leaves for photosynthesis Transpiration water loss in plants primarily lost through stomata evaporation occurs as CO2 must be in a water solution to enter the cells Transpiration stream flow of water through the xylem Embolism air bubble embolized xylem cannot conduct water Cuticle waxy covering on leaf to prevent water loss Guard cells apply tugor pressure around stomata causing closure or opening occurs when K and Cl solute actively accumulate in the guard cells Turgor pressure increases pore opens Stomata openings primary control of transpiration rates respond to water availability light CO2 concentration Cohesion tension theory evaporation at the plant s surface produces a pull tension that is transmitted to the roots by the cohesiveness of water molecules because of their hydrogen bond interactions Driving force is the difference in relative humidity between the inside of the leaf and the air Less solute higher water osmotic potential When the transpiration rate exceeds the water transport capacity from soil a negative pressure is formed Evidence stem diameter shrink during the day and expand at night Humidity increases lower transpiration rate Temperature increases higher transpiration rate Tracheids long and narrow Vessel short and wide Sugars move from source to sink Pressure flow hypothesis claims sugars are transported from sources to sinks by osmotically generated turgor pressure Lecture 15 Hormone substance or chemical that is transported and cause specific physiological effects Auxin 1 Promotes leaf growth branching vascular differentiation root growth fruit growth cell division cell elongation 2 Synthesized in the shoot tip young leaves and seeds 3 Controls plant development 4 Inhibits outgrowth of lateral buds Cytokinins 1 Synthesized in the root tips 2 Stimulate cell division shoot bud initiation leaf expansion 3 Delays leaf senescence 4 Transports through xylem Ethylene 1 Gas hormone made in all parts of the plant 2 Promotes fruit ripening 3 Moves through diffusion Abscisic Acid ABA 1 Synthesized in mature leaves roots developing seeds 2 Transports through xylem and phloem 3 4 Stimulates stomata closure and reduces stress Inhibits premature germination Gibberellic Acid GA 1 Synthesized in young tissue of the shoot and developing seeds 2 Promotes seed germination cell elongation flowering fruit development 3 Was isolated from fungal strains Efflux out of cell
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