An understanding of the 3 Carbon Fixation Plant Categories.
As we found out in the previous chapter, we discovered an idea that this whole C02 thing and all that goes with it is simply life on this planet. Is an ongoing process. However, in this chapter, we will pick up in the area where we left off in the last chapter and go into specific details of each of the 3 main plant types and their relationship to providing the necessary elements for life. In later chapters, we will look into some interesting concepts of applications for us as individuals as well as how it all affects the quality of the plants as well as animal life forms.
The 3 main plant types are the C-3, the C-4, and the CAM types of plants. This nomenclature is of a scientific nature when referencing how the plants take in and process C02, generally into Carbon and Oxygen. This specific naming process and the identification of the Carbon fixing pathways were discovered in the early '60s. Outside of this specific scientific identification process, the plants are sometimes referred to this family name as follows; Mesophytes. For the most part, most C-4 plants fit into this category. When I say most, there are some C-3 plants that have adapted or have developed the ability to function as a C-4 plant or in the conditions of a Mesophyte plant. So as a general rule for understanding we usually refer to Mesophytes as a C-4 type of plant. The Hydrophytes plants or family of plant types are for the most part C-3 type plants. Although the descriptions are not exactly the same in a cross over type of identification, it does help to view them in this aspect in an effort to get your head around the idea for plant identification. Lastly, we have Xerophytes. These can be viewed as a CAM type of plant. I use the term "Generally" as the 3 names and the 3 Carbon fixation pathway plants do not fit hand in glove with each other in the 3 groups on each side, but overall, it does get you into the neighborhood. One must keep in mind that the C-3 type plants cover about 90% of the pants on this planet while the CAM types take in about 3% of the plants on this planet. In some circles, it is claimed that the C-4 plants make up about 3% of the plants as well. But since most groups are in agreement that 90% for C-3 is correct and the 3% for CAM is correct, I fail to see how the C-4 accounts for 3% of the plants. According to my math, the C-4 should be at 7% of the plants worldwide, so we shall go with the C-4 being 7% of the plants worldwide. So, remember, C-3 at 90%, C-4 at 7% of the plants, and CAM at 3%. So those figures should account for 100% of the plants on this planet. Of course, some of these plants within each group have the ability to adapt to a different pathway when conditions require them to do so, but not all plants have this ability.
C-3 type plants;
The C-3 plants do well in the 50, 60 degrees F. range. As the temperature goes down into the '40s and even down to freezing at 32 degrees F., they will grow but will do so very slowly until they freeze. Now on the upper end when the temperature gets up to the 77-degree range, they will grow very well. But at about that 77-degree point, they start slowing their growth and begin to go into dormancy. Most of the time, once they get to the 85-degree range, they will outright just die or be into full dormancy. Now one must keep in mind that we are talking about the temperature at the leaf. If they have any kind of water around the plant or the plant is hydrated sufficiently, then a cooling effect will take place functioning much like an evaporator cooling system might cool the air, and essentially the leaf. But if it is dry, as in no water, then when these plants hit that 86 range, they will die. An example of this is when people try to grow a C-3 type plant in the dry deserts. For example Kentucky Bluegrass. Have you noticed that when you visit an area or even live in one of these full-blown deserts, that a patch of grass will be thriving during the winter months, yet when you see that same patch of grass in the middle of the soaring summer heat these desert environments, by all accounts it looks like someone forgot to water the grass and let it die? The grass isn't dead, as long as there is some moisture in the soil, but rather these C-3 plants, in this case, the grass, has gone dormant. Once the temperatures drop and there is enough moisture in the soil, these plants will come out of dormancy and once again thrive. The only way to keep these plants from going into dormancy in the upper heat range is to water the daylights out of them, or water them enough to keep the leaf temperature down in the 77 degrees or lower range by basically turning the blades of the grass, ie; the leaves into a form of an evaporate cooler. But this is extremely costly by way of resources and at the same time running the risk of creating a disease haven for numerous plant pathogens to thrive and actually kill the plants. This is an illustration of why you need to know this aspect so that you can make the right types of decisions as to what plants to plant for your specific local. In simple terms, a C-3 plant will really struggle in the C- 4 dominant environment during hot summer months. But you can have the C-3 plants during the cooler season in the C-4 environment and do very well with them. You can do well with C-3 type annuals in the cool season of the hot deserts by planting them in the fall when temperatures cool down, if you are in the lower elevations within the southern latitudes of the US, for example. All plants are basically the C-3 type with 2 variations. Those are the CAM and C-4 types. Those will be discussed within the next 2 paragraphs.
C-4 type plants;
The C-4 plants are a type of plant that will do well in the 60 to 100-degree leaf temperature range. They achieve their peak production at about the 90-degree leaf temperature point. Whereas on the lower range, these plants pretty much call it quits at about the 55-degree range. A good example of this the Corn plant. Corn grows well in places like the American Midwest. It gets quite warm and lots of sunlight and at the same time a great deal of water is found there, in the form of high humidity and either natural rain or artificial rain, AKA irrigation. Not to mention the great soils with good electrical conductivity. A C-4 plant is basically a C-3 adapting to a high humidity/hotter and more C02 saturated environment. Unlike a CAM plant, the C-4 plant operates during the daylight hours as does the C-3 plant, but it's internal operational procedural processes are quite different from the C-3's operational processes.
CAM type plants;
When it comes to this type of plant, everything kind of appears in the mirror form of the two previously mentioned plant types, kind of... or well, sort of... or something like that. I say t that way because it is totally different. A CAM plant opens up to take in C02 during the night time. When the sun comes out, it closes up and holds everything in. Since the plant opens up when it gets dark and takes in the C02 and it closes up as the sun shines, the C02 conversion takes place during an overlap period of the darkness and light periods. A CAM plant is a C-3 plant in some ways and a C-4 in other ways, that has adapted to a more hot, less humidity/dryer type environment with lower C02 levels. However, it can adapt to a higher C02 level and/or a higher humidity level with ease. Since most CAM plants are found in desert conditions, they can be found in various other settings. A Pineapple plant is an example of a CAM plant in a higher humidity yet dry soil or lack of soil water holding capacity. The man difference between a CAM plant and a C-3 plant is that the CAM plant's activities primarily take place in the dark. The C-3 activities take place during daylight hours. Their internal operational processes are more similar than dissimilar.
Explanation of operational processes of the 3 Carbon fixation types of plants;
We are focusing on these 3 terms for sake of simplification and in comparing and contrasting. Of course, there are many processes and various cycles, enzymes, and so on in the whole photosynthesis deal. But for this discussion, these are the terms that we are looking at. These ideas with different terms are generalities. Many plants sort of tweak the processes, so let's not get bogged down in technicalities, just keep in mind, the general idea is what our focus is here.
In this section, we will be learning a few new terms. One is RuBisCo. This is the short version of the word, Ribulose 1,5-bisphosphate carboxylase oxygenase. Can you say that word without taking a break to take a breath? That is why it is referred to as RuBisCo. It is an enzyme and it makes up around 50% of the protein in a leaf. It is perhaps the oldest enzyme on earth. It developed long before there was any oxygen in the environment. IE; it works best and most effectively in an Oxygen-free setting. You need to remember this aspect as it is important for what comes along later in this discussion. This enzyme is widely used in the C-3 and CAM plants. But RuBisCo is attracted to Oxygen. As long as Oxygen is not present it works its little hind end off. But when Oxygen shows up, it focuses on the Oxygen and all else does not exist. Think of, in this illustration, as the typical teenage boy jock. He stays focused until that hot looking girl cheerleader shows up on the scene. We shall refer to the hot girl as Oxygen. I think you get the picture as to picturing the attraction.
The next new word is PEPcase. This is short for phosphoenolpyruvate carboxylase. Yeah, again, much easier to just refer to this enzyme as PEPcase. In the C-4 plants, where this enzyme is used. It is very strongly attracted to the carbon dioxide molecule and has no real interest in the oxygen molecule. So with this enzyme, we don't have the losing focus, so to speak, of the task when dealing with carbon fixation as we see with the RuBisCo enzyme in the C-3 plants. This is primarily the main difference. PEPcase is intensely focused and not easily distracted. As an additional concept, the CAM plants use this as well, but under different circumstances. Generally, the CAM plants double-dip in the C-3 as well as the C- 4 pool, taking a little here, a little there, then doing their own thing.
The third term here is Photorespiration. Basically this is used in the C-3 plants as a major function and the CAM plants use it as well, but, again under different circumstances. This is really a nice little safety valve in the process of well over 90 % of the plant species in the world. Basically this identifies the process of the reverse of photosynthesis. This kicks in when RuBisCo has reached a certain point in its process where there begins to be a lot of Oxygen molecules hanging around. So it starts grabbing the more "attractive" Oxygen molecule instead of the Carbon Dioxide molecule. As it does this it shuts down Photosynthesis and reverses the process. Then the plant begins to take in Oxygen and starts creating C02. It sort of senses when it has done its job too well, ie; a build-up of Oxygen, so it reverses and begins to produce C02, so it can maintain a balance of what it, the plant, needs to breathe, ie survive. Basically as long as there are high concentrations of C02 in the air, the likelihood of photorespiration kicking in is very low.
Now let us walk through a simplified version of the processes.
In C-3 plants, they will take in C02, run it through the process of breaking down the C02 by converting the C02 to sugar to feed the root system of the plant, store up Carbon for use in the life cycle of the plant going forward, and then kicking out the trash, ie; leftovers of the process, which is Oxygen. The main enzyme in the C-3 plants, RuBisCo, does really good work when the temperatures are cooler, but as temperatures rise, life gets busy, stress comes in and it looks for an out and grabs an Oxygen molecule. When the Oxygen molecule is placed in the process, the process shuts down to the point of getting some balance and life then begins to make sense. As the C02 levels rise, the signal is given that the rest period is over, then photorespiration stops, RuBisCo gets back to working again. It is really a clever little process that nature has developed. Again, here we see another example of Nature bringing the ratios back into balance.
In C-4 plants, RuBisCo is not the working stiff. We have a different animal, remember the name, PEPcase? PEPcase is working stiff. But unlike the setting of C-3 and RuBisCo doing the heavy lifting, we have PEPcase doing the heavy lifting and heavy lifting, it does very well. It just keeps grabbing a Carbon molecule and it could care less about the attractive Oxygen molecule. So it just keeps working away in the C02 breakdown process. It will keep working until the house burns down, figurative speaking. What I mean by this is that when the plant dies because of processes like dehydration, or even frost, well, remember when the leaf temperature gets down to 55 degrees or so, that 55 degrees are as good as a freeze in the plant's life cycle. But as it gets hotter like in the 100-degree range, these C-4 plants are really pumping out the Oxygen and really taking in the C02. So with the C-4 plants, nature has instructed them on their task and then just turns them loose.
The C-4 plants really do an efficient job. By some accounts just the corn crop going east from the eastern Colorado state line to the east coast, large amounts of Oxygen is produced by the huge amounts of actively growing C-4 plants, IE; corn, maze, etc. In fact, there is more net Oxygen produced in that area than in the Amazon Rain Forest. For some that is an idea that is hard to chew on. But for plant people that understand this stuff, it is essentially a yawn period and then crickets chirping. The reason is this, the Rain Forest is not very efficient at producing Oxygen or taking in C02. Because of the majority of plant types there, namely C-3 plants, and because of the heat and humidity, the RuBisCo cycle is always switching back and forth. In a way, it is a nice balance that is there, but the taking in of C02 and Oxygen production does not do much for the Carbon Sequestration deal from a worldwide perspective. I am betting the people freaking out about Global Warming is not telling you that 90% of the plants on this planet are capable of producing C02 and do it with ease when needed.
By contrast, most of the net Carbon Sequestration and Oxygen production takes place in the Northern Latitudes of Canada, the US, Northern Europe, and Russia/Siberia. Here is why, think, Conifers, which are all C-3 plants, can function in cold weather and low sunlight levels. C-4 plants, well, as before mentioned, call it quits when the temp gets below 55 degrees F. When I say Conifers, I really should say most of these evergreen plants with needles. They can do their Carbon Sequestration in very low temperatures, ie; way below freezing.
Now we will finish up the race here with the CAM plants.
Remember how the CAM type of plants is sort of a mixture of the C-3 and C-4 processes. In parts of the processes, they work like a C-4 but instead of using PEPcase, they use RuBisCo to do the C02 processing. They use the PEPcase pathways, but use RuBisCo in the PEPcase pathways to do the job. They work really well in hot, dry climates and are very efficient at using water. Part of this is due to them doing most of their work at night, it allows for less water evaporation than if they did their processes during daylight hours. As a general rule, they use about 3% of the water that a C-3 plant will use. So very efficient with water. They seem to do best in dry, high alkaline soil. Whereas the C-3 and C-4 plants do much better in acidic soil conditions. I can't help but think that nature evolved these CAM plants to maintain plant life in areas where the cycle has moved from the acidic conditions to the dry, alkaline conditions. I wonder this because it is really important to maintain plant life, even if it contains limited plant varieties, so as when the conditions change, plant life is there and ready to flourish. We will look into this concept in a later chapter. Not only is there not really a limited amount of plant life, as you would be surprised at the massive amounts of plant life found in the CAM plant areas, but we have a vast array of animal life forms as well. These range from simple life forms to complex life forms. Now when you take and put a CAM plant in a controlled environment, such as a greenhouse or even a house, they will grow on average 4 times as fast than they would out in the barren deserts, if proper and consistent care is given to them.
As we try to sum up some takeaways from this whole deal, we can see that I have tried to explain the C-3, C-4, and CAM plant types and some technical aspects to the whole deal and the C02/Oxygen deal. But before we close, let's throw in some fun stuff. You all like fun stuff, right?
Question #1. Did you know that the C02 is so important to the plant's life cycle that in Greenhouse growing situations, for example, they actually have to have these little C02 generation machines? Yes, because at times there isn't enough C02 for the growing plants that they have to generate a somewhat significant C02 so as to keep the plants alive. If you were to see this as a situation as it relates to humans, when Oxygen levels get low, they have to add Oxygen to the environment so the humans don't suffocate. If the plants don't have a certain level on a percentage basis or a PPM basis then they will suffocate. So to solve the problem and help their plants thrive, the C02 generators get turned on. Even with the "excessive" amounts of C02 out there, more has to be generated.
Question #2, Have you ever thought about Vitamin C? Just what is Vitamin C? In the sense of its chemical makeup? Here is the chemical makeup, C6H8O6. This means that Vitamin C is simply made up of Carbon, Hydrogen, and Oxygen. Of course, the numerical numbers are the molecular parts of each. Now when we move the concept over to simple speak, in a somewhat crude sense, Vitamin C is nothing more than a water-soluble Carbon. Go ahead and get your head wrapped around that one. I am sure most of you have at least a concept of how important Vitamin C is for overall health. We have been schooled into thinking that Citrus is the best and most important source for Vitamin C. Of course we can get it from other sources as well.
Question #3, Remember back in the C-3 discussion when I mentioned some C-3 plants are very efficient at Carbon Sequestration???? Well, in this specific case, I am thinking about the Conifers. I want to drag the answers to question #2 into the answers/comments on this question. So, in some of my "live" discussions when it is brought up about Vitamin C or Carbon, etc., I have done my little-used car salesman act. It goes like this; For those of us that don't have easy access to high-quality, fresh Citrus, we have to look to other alternatives. Guess what, I have that alternative. What if I told you I can provide you with a solid Vitamin C source other than Citrus? Would you be interested? This source is not the same as, it is not 2X the amount of Vitamin C, not 3X, not 4X, but on average 5X the amount of Vitamin C than Citrus! It is so simple and it tastes good too. Guess what? That source is Conifer Needles, or rather more technically Conifer Leaves. Needles are leaves, BTW. All it takes is a 6-inch stem of pine needles. Make a cup of Herbal Tea with it. It actually tastes really good, even without any sweeter.
So to recap this idea, a Conifer is really efficient at sequestering Carbon and storing it. Plants will always take in minerals and arrange them in proper ratios and prepare them for our use. So when you make an Herbal Tea, and to make a really good drink, you need to keep the water below 160 degrees F. Then as soon as it has cooled enough to drink it, then drink it. If you get the water too hot, say like boiling, then you release the Terpenes, and they make the tea taste nasty. New shoots make for a better tasting tea. Although the Terpenes are excellent for some uses and just to give you a little teaser... Why do you need Tea Tree oil when you have these Conifer Needles? Anyway, moving on... In another chapter, we will examine this concept and idea.
As we close this chapter, I hope you have a general concept/idea of the 3 plant categories that Carbon Fixation takes place. We will refer to these concepts in later chapters. I hope this chapter is clearing in being able to get your head around these ideas than chapter one was. In chapter one, we had to hit on a very wide range of ideas to enable us to set the stage for succeeding chapters. Just to add a comment here, to confirm my bias in this line of reasoning, I am working from an old school line of thinking. The "New" line of thinking will rip these ideas to shreds. In some situations, the "newer" line of reasoning can be more on the money than the old school stuff. But when it comes to some of this stuff as discussed in these chapters, I feel like the old school line of thinking is the most rational. The reason is this; the newer lines of thinking are too politically charged. Political correctness has required the scientific line of rational to be tweaked to fit the political agendas of the radical thinkers, so much so that if it doesn't fit the politically correct line of thinking, it must be trashed. So if you feel I am out to lunch, then help me to see the light of day on this. Otherwise, work with this stuff, you will be better off and not so freaked out because the sky is falling, according to some people anyway. Until the next chapter, I wish you well.
End of Chapter Two.