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Stomatal movement in succulents copy

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Stomatal movement in succulents copy

  1. 1. STOMATAL MOVEMENT IN SUCCULENTS
  2. 2. SUCCULENTS • Latin word- sucus, means juice or sap • Found in water arid climates or soil conditions • absent, reduced, or cylindrical-to-spherical leaves • reduction in the number of stomata
  3. 3. • stems as the main site of photosynthesis, rather than leaves • compact, reduced, cushion-like, columnar, or spherical growth form • ribs enabling rapid increases in plant volume and decreasing surface area exposed to the sun • waxy, hairy, or spiny outer surface to create a humid micro-habitat around the plant, which reduces air movement near the surface of the plant, and thereby reduces water loss and creates shade
  4. 4. • roots very near the surface of the soil, so they are able to take up moisture from very small showers or even from heavy dew • ability to remain plump and full of water even with high internal temperatures (e.g., 52 °C or 126 °F) • very impervious outer cuticle (skin) • mucilaginous substances, which retain water abundantly
  5. 5. Sunken stomata in succulents
  6. 6. Crassulacean Acid Metabolism (CAM) in succulents • Observed by Botanists Rason and Thomas in late 1940s • Its name refers to acid metabolism in Crassulaceae not the Crassulacean acid.
  7. 7. What is crassulacean Acid Metabolism? • It is a carbon pathway • Also known as CAM photosynthesis • These plants fix carbon dioxide (CO2) during the night, storing it as the four carbon acid malate • The CO2 is released during the day, where it is concentrated around the enzyme RuBisCO, increasing the efficiency of photosynthesis. • The CAM pathway allows stomata to remain shut during the day, reducing evapotranspiration; therefore it is espicially common in plants adapted to arid conditions.
  8. 8. • CAM plants is subset of C4 plants • The fixation now occurs in mesophyll cells so that they will be more exposed to the air & in order to take in more CO2. • The malate, which is the product of the fixation process is pumped deeper in the leaf so that it won’t be exposed to air and to oxygen. • This is to avoid photorespiration and the wasteful process since RuBisCo is used in the Calvin cycle • The process is a lot like the C4 pathway.
  9. 9. Overview of CAM A two part cycle
  10. 10. During night • CAM plant’s stomata are open ,allowing CO2 to enter and be fixated as organic acids that are stored in vacuoles. • The carbon dioxide is fixed in the mesophyll cell’s cytoplasm by PEP reaction • PEP- Phosphoenolpyruvic acid
  11. 11. During day • During the day the stomata are closed and the carbon is released to the Calvin cycle so that photosynthesis may take place. • The carbon is the organic acids is freed from the mesophyll cell’s vacuoles and enters the chloroplast’s stoma and into Calvin cycle .
  12. 12. Comparison chart Plant characters C3 pathway C4 pathway CAM pathway Photorespiration rate High Low/ negligible Very low/ negligible Leaf anatomy Typical Kranz Xeromorphic Typical environment All Tropical, elevated daytime temperature, drought Dry, arid Stoma open during the day? Yes Yes No No. of steps in pathway 1 2 2 First molecule produced in pathway 3-phosphoglyceric acid Malic acid or aspartic acid Malate Uses the Calvin cycle yes yes Yes

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