Botany B/C [TRIAL]

[dankdecidueye]

Hey everyone!

I hope everyone is having a great season so far. Here are two questions to get this thread started.

1. Describe the nitrogen cycle and each step.
2. What is the purpose for the central vacuole in a plant cell?

[RiverWalker88]

I need to touch up on my plant skills...

Click to Show Answer

[list=1]
[*] The Nitrogen Cycle describes the cycle through which nitrogen changes and cycles through the environment.
 Step 1: Nitrogen Fixation In this step, nitrogen gas from the atmosphere is turned into ammonia.
 Step 2: Nitrification In this step, ammonia is turned into nitrate, with soil bacteria.
 Step 3: Assimilation In this step, plants' roots take in nitrates and turn use them in amino acids and nucleic acids.
 Step 4: Ammonification In this step, soil bacteria decompose dead plants' and animals' amino acids and nucleic acids to release the nitrates and ammonia back into the soil.
 Step 5: Denitrification In this step, anaerobic bacteria turn nitrates back into nitrogen gas, which gets released back into the atmosphere.

[*] To maintain turgor pressure, which will keep the plant cell rigid.
[/list]

[RiverWalker88]

Say we discover a planet that is completely covered with plant life (like, completely covered) that happens to exactly resemble plant life on Earth. Additionally, said planet also has life forms that can turn CO₂ into oxygen to keep the planet habitable for these plants. By taking measurements of its atmosphere, we are able to determine something strange: at night the CO₂ levels decrease, but during the day, they increase.

1. What might this tell us about the nature of the photosynthesis completed by plants on this planet?
2. Furthering, what might we be able to conclude about the climate of this planet?

Edit: There are some assumptions you have to make...

[Krish2007]

Say we discover a planet that is completely covered with plant life (like, completely covered) that happens to exactly resemble plant life on Earth. Additionally, said planet also has life forms that can turn CO₂ into oxygen to keep the planet habitable for these plants. By taking measurements of its atmosphere, we are able to determine something strange: at night the CO₂ levels decrease, but during the day, they increase.

1. What might this tell us about the nature of the photosynthesis completed by plants on this planet?
2. Furthering, what might we be able to conclude about the climate of this planet?

Edit: There are some assumptions you have to make...

I love your idea for this question!
1)I can assume that they are CAM plants, or crassulacean acid metabolism plants. Since the CO2₂ levels decrease at night, we know that the stomata must be opening at night (a characteristic of CAM plants). CAM plants store CO₂ in organic acids until the day, where they are broken down for photosynthesis, and in that time, the other organisms increase the CO₂ levels
2)We can assume that the climate of the planet is hot and/or dry, like a desert on Earth, since CAM plants are adapted to reduce water loss.

[RiverWalker88]

Say we discover a planet that is completely covered with plant life (like, completely covered) that happens to exactly resemble plant life on Earth. Additionally, said planet also has life forms that can turn CO₂ into oxygen to keep the planet habitable for these plants. By taking measurements of its atmosphere, we are able to determine something strange: at night the CO₂ levels decrease, but during the day, they increase.

1. What might this tell us about the nature of the photosynthesis completed by plants on this planet?
2. Furthering, what might we be able to conclude about the climate of this planet?

Edit: There are some assumptions you have to make...

I love your idea for this question!
1)I can assume that they are CAM plants, or crassulacean acid metabolism plants. Since the CO2₂ levels decrease at night, we know that the stomata must be opening at night (a characteristic of CAM plants). CAM plants store CO₂ in organic acids until the day, where they are broken down for photosynthesis, and in that time, the other organisms increase the CO₂ levels
2)We can assume that the climate of the planet is hot and/or dry, like a desert on Earth, since CAM plants are adapted to reduce water loss.

Yep! All correct! Glad you liked the question.

[Krish2007]

1) What 2 types of cells make up the xylem of a vascular plant? Are they dead or alive at maturity?
2) What are companion cells?
3) What is the Casparian strip and what is its purpose?
If you don't realize from my questions, I really like plant anatomy.

[Mayur917]

1) What 2 types of cells make up the xylem of a vascular plant? Are they dead or alive at maturity?
2) What are companion cells?
3) What is the Casparian strip and what is its purpose?
If you don't realize from my questions, I really like plant anatomy.

Click to Show Answer

1. Tracheids and Vessel Elements. Tracheids, at functional maturity, are still "alive". In other words the cells are dead but their function as supporting structures (thickened walls) are still alive. The organelles inside of the dead cells have disintegrated, allowing for more water and mineral transportation. Same goes with vessel elements; their functions remains intact and they are dead at maturity.

2. Companion cells are found in sieve-tube elemental structures. They are parenchyma cells which load starches and unload them to neighboring sieve-tube members via plasmodesmata.

3. Casparian strips are bands of cells walls made out of suberin that are radially and transversally located in each endodermal cell. It acts as a barrier to keep many toxic and unneeded substances out of the endodermis transport. The apoplastic pathway directly uptakes soil solutions  into the apoplast whereby water and minerals cross the selectively permeable membrane of an endodermal cell. Water and minerals entering the symplast is known as the symplastic pathway. The Casparian strips block any water and dissolved minerals that haven't entered the symplast. It's like a check to protect plants. Be sure to look into how Casparian strips also play a role in root pressure- prevents ions from leaking back out into the root cortex and soil.

[Krish2007]

1) What 2 types of cells make up the xylem of a vascular plant? Are they dead or alive at maturity?
2) What are companion cells?
3) What is the Casparian strip and what is its purpose?
If you don't realize from my questions, I really like plant anatomy.

1. Tracheids and Vessel Elements. Tracheids, at functional maturity, are still "alive". In other words the cells are dead but their function as supporting structures (thickened walls) are still alive. The organelles inside of the dead cells have disintegrated, allowing for more water and mineral transportation. Same goes with vessel elements; their functions remains intact and they are dead at maturity.

2. Companion cells are found in sieve-tube elemental structures. They are parenchyma cells which load starches and unload them to neighboring sieve-tube members via plasmodesmata.

3. Casparian strips are bands of cells walls made out of suberin that are radially and transversally located in each endodermal cell. It acts as a barrier to keep many toxic and unneeded substances out of the endodermis transport. The apoplastic pathway directly uptakes soil solutions into the apoplast whereby water and minerals cross the selectively permeable membrane of an endodermal cell. Water and minerals entering the symplast is known as the symplastic pathway. The Casparian strips block any water and dissolved minerals that haven't entered the symplast. It's like a check to protect plants. Be sure to look into how Casparian strips also play a role in root pressure- prevents ions from leaking back out into the root cortex and soil.

All correct.
Your turn!

[Mayur917]

I won't ask anything too difficult.
Also, for those who took my UT Invitational Examination, I **think** it would be fine to discuss some of the questions here since I'll be publishing the exam here and so will ATX SciOly on their website!

1. What is the general trend behind altitude and % of C3 and C4 species, respectively?
2. Do some C4 plants grow in tundras?
3. One of the answers to my exam was "Facultative CAM". Someone please explain what that is? I'd love to hear from anyone here.