Leaf Structure and Function Lecture Notes

Leaf Structure / Function Worksheet: 1. Explain the difference between an autotroph and a heterotroph: Autotrophs have to make their own food for energy and heterotrophs have to consume food to make energy. 2. What is the primary function of the mesophyll cells of leaves? They allow carbon dioxide to move freely 3. About how many chloroplast organelles does a typical mesophyll cell have? 80-120 4. About how many chloroplast organelles are there per square millimeter of leaf? Half a million 5. Write the simplified equation of photosynthesis by indicating only the net consumption of water: 6CO2+6H20+light --> C6H12O6 +6O2 The overall chemical change during photosynthesis is the reverse of the one that occurs during cellular respiration. Both of these metabolic processes occur in plant cells. The chloroplast organelle is the site of photosynthesis. 6. What specific organelle is the site of cellular respiration in plants and animal cells? The mitochondria 7. What microscopic pores on the surface of a leaf allow gases to enter and exit the leaf? Stoma 8. What gas needed for photosynthesis enters the leaf through these microscopic pores? Carbon dioxide 9. What photosynthetic end product gas escapes out of the leaf through these microscopic pores? Oxygen 10. Highlight the correct answer. The mesophyll region of a leaf is sandwiched between the upper and lower epidermal layers. Recall that the mesophyll layers contain parenchyma cells specialized for photosynthesis. The specific mesophyll layer that has air spaces between the irregularly shaped parenchyma cells which allow the gases to circulate throughout the interior of the leaf is called the ( spongy or palisade ) mesophyll. (Because of the irregular shapes of these cells, the leaf’s internal surface area may be 10 to 30 times greater than the external surface area.). The specific mesophyll layer that forms the upper half of the leaf and is made up of parenchyma cells that are columnar in shape is called the ( spongy or palisade ) mesophyll. 11. Water absorbed by the roots is delivered to the leaves in veins (also called vascular bundles). What specific tissue in the vascular bundle transports water to the leaf cells? Xylem 12. Leaves also use veins (vascular bundles) to export sugar to roots and other plant areas. What specific tissue in the vascular bundle transports the end product of glucose (as sucrose) away from the leaf (to be used as an energy source or for storage as starch)? Phloem 13. Highlight the correct answer. Leaves generally have a ( low or high ) surface area-tovolume ratio. In what ways does this ratio help to increase the rate of photosynthesis? This would help photosynthesis because it would help the leaves absorb maximum sunlight. 14. About what percent of a plant’s water loss occurs through the stomata? 50-90% 15. What specific cells flank the pore of a stoma and regulate the opening and closing of these pores? Guard cells 16. Highlight the correct answer. When these cells are turgid (full of water), the size of the pore ( decreases or increases ). 17. Discuss whether stomata are generally open during the night as well as the day and the reason why. Stomata open during the day to do the most photosynthesis and do the most CO2 diffusion and close at night to save water. 18. For any land plant, dehydration is always an issue. What layer is secreted by the epidermal cells that helps reduce the amount of water lost to evaporation? (pp. 620, 761) Plants develop a cuticle to help reduce water loss. 19. Name three cues that contribute to why stomata will open: a. Sunlight b. CO2 depletion c. Guard cells 20. What circumstances can cause stomata to close during the daytime when they are generally open? Drought