Plants are some of the most important organisms on the planet; they form the foundation of numerous ecosystems and environments. Although they appear as relatively simple organisms, there are many complex processes occurring within all plants. Many of these processes involve the application of physical laws and principles. Plants rely on light absorption as well as electron excitation to produce chemical energy and use osmosis to transport the products.
A plant’s source of chemical energy is glucose formed through photosynthesis (Lambers, Chapin and Pons, 2008). Photosynthesis is carried out within chloroplasts, which are specialized organelles containing chlorophyll (Palta, 1990). There are two types of the pigment: chlorophyll a and b. Chlorophyll a is a blue-green colour, while chlorophyll b is a yellow-green colour. Chlorophyll a and b have characteristic wavelengths of 660 nm (red light) and 450 nm (blue light), respectively, while both transmitting green light (Palta, 1990). The basis of photosynthesis is connected with two photosystems within chloroplasts where chlorophyll is found (Lambers, Chapin and Pons, 2008). The pigments absorb incoming photons of light and become excited in the reaction center (Figure 1), (Krause and Weis, 1991). The excited chlorophyll molecules are then in an unstable state of higher energy. This energy from the photon then moves through the two photosystems in the form of electron movement. This movement occurs along an electron transport chain in order to develop an electrochemical gradient (Wege, 2020). This electrochemical gradient is used by the enzyme ATP synthase to produce ATP (Wege, 2020). ATP is then used as one of the sources of energy for further cellular processes to turn carbon dioxide in the atmosphere into glucose to be used by the plant as nutrition (Wege, 2020).
The movement and distribution of substances within plants is accomplished by yet another set of physical mechanisms. The glucose formed using the energy from photosynthesis must be transported to other locations of the plant; this is done through bulk liquid flow via phloem (Jensen, 2018). Phloem is a type of vascular tissue that is responsible for the movement of materials and fluid dynamics throughout plants. Phloem tubes compose the system responsible for glucose transport and is driven by pressure differences (Jensen, 2018). Osmosis is responsible for generating the motile force of phloem pressure. The accumulation of glucose areas with high rates of photosynthesis causes an increase in turgor pressure (Jensen, 2018). Turgor pressure is a measure of the water volume and osmotic pressure of a cell (Sheng-Xu, Zhao-Hui and Stewart, 2013). A pressure of 1 megapascal is enough to allow the transport of glucose in small plants (Jensen, 2018). However, as the size of the organism increases, so does the required amount of pressure to force glucose transport. The glucose molecules are moved into the vascular tissue via membrane transporters (Jensen, 2018). This process requires energy since the phloem may have a higher glucose concentration than the photosynthetic cells. The glucose is then moved through the plant in the phloem tubes to be used by other cells as nutrients (Jensen, 2018).
The use of physical phenomenon, such as light absorption and osmosis, for natural purposes is extensively displayed in plants. The mechanics of energetically exciting chlorophyll in photosystems and osmotic transport of the resulting energy product is vital to a plant’s proper functioning. The multifaceted processes that plants make use of is a demonstration of their, at first unapparent, complexity.
References
Jensen, K.H., 2018. Phloem physics: mechanisms, constraints, and perspectives. Current Opinion in Plant Biology, 43, pp.96–100. https://doi.org/10.1016/j.pbi.2018.03.005.
Krause, G. and Weis, E., 1991. Chlorophyll Fluorescence and Photosynthesis: The Basics. Annual Review of Plant Physiology and Plant Molecular Biology, 42(1), pp.313–349. https://www.annualreviews.org/doi/abs/10.1146/annurev.pp.42.060191.001525.
Lambers, H., Chapin, F.S. and Pons, T.L., 2008. Photosynthesis. In: H. Lambers, F.S. Chapin and T.L. Pons, eds. Plant Physiological Ecology. [online] New York, NY: Springer. pp.11–99. https://doi.org/10.1007/978-0-387-78341-3_2.
Palta, J.P., 1990. Leaf chlorophyll content. Remote Sensing Reviews, 5(1), pp.207–213. https://doi.org/10.1080/02757259009532129.
Photosystem. 2006 [image online] Available at: <https://commons.wikimedia.org/wiki/File:Schema-photosysteme.svg> [Accessed 20 November 2022]
Sheng-Xu, L., Zhao-Hui, W. and Stewart, B., 2013. Responses of Crop Plants to Ammonium and Nitrate N. 118. In: Advances in Agronomy. pp.205–397. Available from> https://doi.org/10.1016/B978-0-12-405942-9.00005-0.
Sujatha, B., 2015. Photosynthesis. In: B. Bahadur, M. Venkat Rajam, L. Sahijram and K.V. Krishnamurthy, eds. Plant Biology and Biotechnology: Volume I: Plant Diversity, Organization, Function and Improvement. [online] New Delhi: Springer India. pp.569–591. https://doi.org/10.1007/978-81-322-2286-6_22.
Wege, S., 2020. Plants Increase Photosynthesis Efficiency by Lowering the Proton Gradient across the Thylakoid Membrane. Plant Physiology, 182(4), pp.1812–1813. https://doi.org/10.1104/pp.20.00273.
Comments
7 Responses to “The Physics of Photosynthesis”
Hello everyone!
I decided to do my blog post based on the integration of physics in the natural world of plant biology because this topic has always been of interest to me. We have discussed photosynthesis is first year and other physical aspects of plants this year as well. So I decided to link the topic with the concepts discussing light from our neuroscience lectures. The physics of light absorption as well as the physical movement of molecules within liquid are closely related in plants, which is what I describe in my post.
I hope you enjoy!
-Aunika
Hi Aunika,
I really enjoyed reading your blog post and I liked how you brought physics in to explain photosynthesis. I have a few suggestions for you:
– In your first paragraph second sentence I think you should change your phrasing from “Although they appearance as relatively simple organisms” to maybe say “Although they appear to be relatively simple organisms”
– In the third sentence of your first paragraph I think you should change the word integration or reword the sentence maybe it was just me but when I see integrate I think that you are referring to integrating different subjects to explain the process, maybe say application instead of integration
– In your next sentence of your introduction you mentioned “those organic products” but I think you should clarify what organic product you are referring to
– Just a small thing but the beginning of the second sentence of your second paragraph has two spaces after the period. Same thing with sentence 8 of paragraph 3
– In the second sentence of your third paragraph I think you should consider removing the word then
Looking forward to reading the final version,
Kiran
Hi Aunika,
Great post! I really like how you showed the complete process of both glucose synthesis and transport.
I just have a few suggestions:
1. In the first sentence you say “Plants are perhaps the most important organism” this reads a little awkward since plants is plural and organism is singular. To fix this I would says “organisms” or even “system of organisms”.
2. In the next sentence I believe “appearance” should be “appear”
3. In your final sentence, I think you want a comma before “at” since this part of the sentence could be removed and you would still have a functional sentence.
4. Make sure you have citations whenever you claim something; the ending of both body paragraphs seem to be missing citations.
Happy editing,
– Lily
Hi Aunika,
This was a really interesting blog post! It is clear you have made this post very integrated by combining plant ecology with physics concepts and still made the writing very engaging. After reading your draft, I do have a few suggestions that I believe you can use for your final draft:
1. The pressure measurement of 1megapascal for smaller plants was really interesting, but could you provide some more context as to what plants have this pressure value? That would help the reader understand the value a bit more.
2. You have a lot of great information in this post but I think adding a Figure would help you explain the electron transport chain in photosynthesis. This concept is a bit hard to visualize so one Figure would be a great addition there.
3. In your final sentence, I think a better word choice for “at first” would be “originally”.
4. A small edit: in the final sentence of your second paragraph, I think you forgot to add a space before the word “ATP”. You can easily correct this when you get a moment.
In summary, I thought this blog post was very good. You brought up a completely original topic, researched well, and communicated your ideas in an orderly manner. I hope the comments I provided give you some idea as to what you can improve for your final draft, and I cannot wait to read what you post next.
Happy editing,
Rith
Hi Aunika,
This was a really cool post, you took the reader through these applications in a very clear and thorough manner and it was highly captivating. Great work! Here are a few notes to consider:
1) I think you should add a “For instance,” to the beginning of the last sentence of your first paragraph just to increase flow.
2) This may be personal preference, but to me it seems like you may be missing a few commas throughout. For example, I’ll use the first few sentences of the second paragraph, I think you should add commas separating the words (i.e., glucose, chloroplasts) and their definitions/explanations.
3) Also there is a double space before the start of your second sentence in paragraph two and After your (Sheng-Xu, Zhao-Hui and Stewart, 2013) citation in paragraph three.
4) As Rith said above, I think a figure would really help tie the post together. Maybe consider adding a picture of a plant and these plant systems or even show a diagram of the pigment and energy (ATP) movement.
Overall great work. Your post was well researched, flowed nicely and with a few minor edits I’m sure it’ll be amazing! I can’t wait to read your final draft.
Happy editing,
Sarah
Hi Aunika,
I was very excited to see that you wrote about physics! What a wonderful blog post!
Here are a few suggestions I have:
– I agree with all of the above comments!
– The content is relevant to physics, but I would love it if you expanded the physics further and stated the specific physics concepts that are within your topics:
– For the light absorption, the photoelectric effect is very relevant. Here is a paper that explains it in regards to photosynthesis (https://www.sciencedirect.com/science/article/abs/pii/S0376738800801702) and you can also find the photoelectric effect in our old physics notes- check the modern physics section:)
– As well, using the key term fluid dynamics when describing the phloem will make it more “physics.” Here is a paper that explains fluid dynamics in plants (https://academic-oup-com.libaccess.lib.mcmaster.ca/jxb/article/70/14/3533/5518960)
– If you’re struggling to find a figure (although I think the photosynthesis and the chlorophyll would be a great figure!) you could always use an equation and then describe this, which would also make your blog more visually “physics,” possibly an equation or schematic for osmosis.
Overall terrific work!
– Clara
Hello everyone,
Thank you for all your suggestions! I have made all the grammatical changes you have suggested as well as added a figure. I decided to add a figure of the absorption of the photon into the photosystem rather that the electron transport chain. This is because the absorption of the photon was the main focus of that paragraph since it is most relevant to the physics portion of how glucose is made. I did not have the word count to add more about the electron transport chain and a figure concerning this would show more than I discussed since the electron transport chain is complex.
Thanks again for your comments!
-Aunika