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botany exam 2
| What kind of modified stem is a stolon (runner?) | Stolons are above-ground, horizontal stems (ex. strawberries) |
| What kind of modified stem is a rhizome? | Below-ground stems (ex ginger, iris) |
| What kind of modified stem is a tuber? | A stem for underground storage (ex. potato. Hint: eyes are axillary buds) |
| What kind of modified stem is a bulb? | A below-ground stem with fleshy leaves, used for food storage. (ex. onion) |
| What kind of modified stem is a corm? | A below-ground stem with dry leaves |
| What kind of modified stem is a cladophyll? | A photosynthetic stem (ex. cacti) |
| What kind of modified stem is a tendril? | A stem used for support and latching on (ex. grapes) |
| What is transpiration? | The loss of water through stomata |
| How can stomatal control and position reduce transpiration? | Stomata can be located on the bottom surface of leaves to reduce respiration, because they aren't being hit with direct sun and dry wind. They can also close when conditions are causing them to lose too much water, such as the hot noon sun. |
| How can leaf size and shape reduce transpiration? | A smaller leaf means less exposure to the sun. Cylindrical leaves (ie pine needle) reduce the surface area : volume ratio. Thicker leaves (ie succulents) also reduce the surface area: volume ratio. |
| What does having a smaller surface area : volume ration mean for leaves? How does it help reduce transpiration? | Smaller sa/v means that there is less leaf surface being exposed to hot/dry conditions compared to the amount of internal volume. This means the barrier for water vapor to escape through is smaller. |
| Name three types of modified epidermis which help regulate transpiration by minimizing water loss. | Trichomes (trapping moisture), extracuticular wax (keeping in moisture), multilayered epidermis (keeping in moisture) |
| How do plants with a multilayered epidermis photosynthesize and perform gas exchange through the thick layers? | They have sunken stomata and/or stomatal crypts |
| Do sun leaves or shade leaves have a smaller surface area to volume ratio? Why? Which leaves are smaller in size? | Sun leaves have a smaller sa/v ratio, because they're towards the top of the plant and are more exposed to sun. This means they want less surface area to lose water through. Sun leaves are also smaller than shade leaves for the same reason. |
| What pigment do all plants have? What are the two common accessory pigments? | All plants have chlorophyll a for photosynthesis. Common accessory pigments are chlorophyll b and carotenoids. |
| What is the chemical reaction of photosynthesis? | CO2 + H2O --> C6H12O6 + O2 (carbon dioxide + water --> glucose + oxygen) |
| Briefly describe the movement of energy in light dependent reactions. | Starting in Photosystem II, bouncing around the antenna complex to the reaction center. From there, electrons are passed on to an electron acceptor, which passes the energy on to PS I where the same process happens. Then, it's passed into the stroma. |
| What are the three stages of the Calvin Cycle (aka C3 Path) in Photosynthesis? | Carbon fixation, Reduction, Regeneration |
| What happens during the Carbon Fixation stage of the Calvin Cycle? | CO2 and RUBP are catalyzed by the RUBISCO enzyme to form PGA (a 3 carbon compound). |
| What happens during the Reduction stage of the Calvin Cycle? | ATP and NADH from the light dependent reactions are reduced. PGA is reduced into PGAL, which can be used to continue the cycle or to create photosynthetic products like sugars. |
| What happens during the Regeneration Phase of the Calvin Cycle? | ATP is used to make RUBP from PGAL, and the cycle begins anew. |
| How can the RUBISCO enzyme cause photorespiration, under certain conditions? | RUBISCO will use CO2 as a substrate to begin the Calvin Cycle when there are high amounts of CO2 in the environment. But when supplies are low, it will start reacting with O2 instead-- performing photorespiration instead of helpful photosynthesis. |
| What are two alternate paths that plants use instead of the C3 path to reduce the risk of photorespiration? How do the two paths differ from one another? | Two alternate paths are the C4 pathway (which is spatially separated) and the CAM pathway (which is temporally separated) |
| Describe the process of the alternate photosynthesis C4 Pathway. | In the mesophyll cell, CO2 and PEP are catalyzed by PEP carboxylase . ATP is used to create malate, which passes to the bundle sheath cell. From there malate can start the Calvin cycle, or turn into pyruvate to and go back to the mesophyll to restart C4. |
| Describe the process of the alternate photosynthesis CAM Pathway. | At night, the CAM plant opens stomata to get CO3 to fixate using PEP carboxylase, and turns it into malate to store. During the day, the stomata are closed, and the stored malate is used to go through the C3 process. |
| What are the pros and cons of the C3 pathway of photosynthesis? | Adapted to cool temperatures, but photorespiration at high temperatures because of RUBISCO. |
| What are the pros and cons of the C4 pathway of photosynthesis? | Avoid photorespiration at high temperatures by using PEP carboxylase, but sensitive to cold temps. |
| What are the pros and cons of the CAM pathway of photosynthesis? | Avoid photorespiration at high temperatures by using PEP carboxylase and closing the stomata during the day, but lower photosynthetic rates because they're limited to how much they stockpiled during the night. |
| What is the functional significance of spongy mesophyll? | The extra air space allows carbon dioxide to diffuse more easily. |
| How does the shape of palisade mesophyll help reduce transpiration? | They are tightly packed, which helps prevent water loss. |
| Where does the majority of photosynthesis occur in a leaf? | In the mesophyll |
| In which climates or conditions would you find each of the following type of plant: Mesophytes, xerophytes, hydrophytes | Mesophytes in moderate climates. Xerophytes in dry climates (or periods of low moisture). Hydrophytes in or near water. |
| Why do leaves change color in the fall? | As winter arrives, there is less light, so plants no longer invest energy in maintaining leafy photosynthesis. As the green chlorophyll pigments for photosynthesis disappear, it leaves behind only the orange-yellow-brown accessory pigments. |
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clownestate
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