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C4 And Cam Photosynthesis Free Response Essay Enzymes

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Key Differences Between C3, C4 and CAM Photosynthesis

Key Differences Between C3, C4 and CAM Photosynthesis

The key differences between C3, C4, and CAM photosynthesis are seen in the way that carbon dioxide is extracted from sunlight. Plants, algae, and many species of bacteria utilize one of these photosynthetic processes in a chemical reaction that creates energy. Whether an organic compound uses C3, C4, or CAM photosynthesis depends largely on the conditions of the organic compound's habitat.

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In photosynthesis, plants and other organic compounds use the energy from sunlight to extract nutrients from air and water. Photosynthetic organisms feature a green compound known as chlorophyll that contains the enzymes ATP and NADPH. With the energy absorbed from sunlight, photosynthetic compounds convert these enzymes to ADP and NADP+. The energy from the converted enzymes is used to extract carbon dioxide from air and water, which is then used to produce sugar molecules such as glucose. Through photosynthesis, plants excrete waste molecules including oxygen, which makes the air breathable for animal organisms.


Photosynthetic organisms that undergo C3 photosynthesis begin the process of energy conversion, known as the Calvin cycle, by producing a three-carbon compound called 3-phosphoglyceric acid. This is the reason for the title "C3." C3 photosynthesis is a one-stage process that takes place inside of the chloroplast organelles, which act as storage centers for sunlight energy. The energy is then used to combine ATP and NADPH into ordered sugar molecules. Roughly 85 percent of the plants on earth utilize C3 photosynthesis.


C4 photosynthesis is a two-stage process in which a four-carbon intermediate compound is produced. The photosynthetic process occurs in the chloroplast of a thin-walled mesophyll cell. Once created, the intermediate compound is pumped into a thick-walled bundle sheath cell, where the compound is split into carbon dioxide and a three-carbon compound. The carbon dioxide then undergoes the Calvin cycle, as in C3 photosynthesis. The benefit of C4 photosynthesis is that it produces a higher concentration of carbon, making C4 organisms more adept at surviving in habitats with low light and water.


CAM is an abbreviation of crassulacean acid metabolism. In this type of photosynthesis, organisms absorb sunlight energy during the day, then use the energy to fix carbon dioxide molecules during the night. During the day, the organism's stomata close up to resist dehydration, while the carbon dioxide from the night prior undergoes the Calvin cycle. CAM photosynthesis allows plants to survive in arid climates, and therefore is the type of photosynthesis used by cacti and other desert plants. However, CAM photosynthesis is also observed in non-desert plants including pineapples and epiphyte plants such as orchids.

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Term Paper on C4 and Cam Photosynthesis

"Beauty is in the eye of the beer-holder." - Affluxlove?

C4 and Cam Photosynthesis
  1. Photosynthesis C3,C4 And Cam Plants in plants and algae: they absorb light energy for use in photosynthesis, and they protect chlorophyll from photodamage. In humans, four carotenoids (-carotene.
  2. Light Reaction Of Photosynthesis are both the same in all types of photosynthesis. As opposed to C3photosynthesis, C4 photosynthesis and CAM photosynthesis first fix carbon dioxide into four–carbon.
  3. Biology 1 and 4 positions in -glucose cause every other monomer to be inverted for the glycosidic linkage to form. Unlike amylose and amylopectin, cellulose molecules are.
  4. Photosynthesis crabgrass takes over in hot midsummer). 6. CAM Photosynthesis a. CAM (crassulacean-acid metabolism) plants form a C4 molecule at night when stomates can open.
  5. Photosynthesis In CAM photosynthesis, CO2 is taken up only at night and is stored in vacuoles. This causes a build up of oxaloacetate (acidic) - which we just met in C4.

Date Submitted: 04/26/2011 06:59 PM Flesch-Kincaid Score: 45.9 Words: 692 Essay Grade: no grades Flag

C4 and CAM photosynthesis are considered advantageous to plants that exhibit them because of the special “add-on” features they display. C4 photosynthesis reduces photorespiration and water loss. The reduction of photorespiration is due to the fact that carbon dioxide is moved to a specialized cell known as a bundle sheath cell which surrounds the leaf veins and they themselves are surrounded by mesophyll cells. (Photosynthesizing cells) Bundle sheath cells rarely ever come in contact with an intercellular space thus minimal oxygen reaches them. This lack of oxygen allows rubisco to fix with carbon dioxide without having to compete with oxygen. Therefore, little photorespiration takes place and photosynthesis is more efficient.
The higher rates of photosynthesis in C4 plants allow them to reduce the amount of time their stomata are open which reduces water loss. (Stomata open to allow carbon dioxide to enter) This advantage allows C4 plants to live in dry, arid climates such as deserts. Examples of C4 plants include sugarcane and crab grass.

CAM plants follow a similar pathway to C4 plants with some minor differences. Instead of OOA (oxaloacetate) being converted into malate, it is converted into malic acid. The malic acid is then transported to the vacuole of a cell instead of bundle sheath cells like in a C4 plant. The main advantage of CAM plants is that their stomata are open at night which greatly reduces water loss. During this time, the malic acid is transported out of the vacuole and converted back to OOA, releasing carbon dioxide. The carbon dioxide is fixed with rubisco and photosynthesis can proceed during the day.

Three major differences between C3 photosynthesis and C4 and CAM photosynthesis are the fixing enzymes they use, their production rates, and their ability to adjust to arid climates. C3 photosynthesis uses the fixing enzyme rubisco to fix carbon dioxide into PGA. However, both C4 and CAM.


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C3, C4 Photosynthesis, and CAM

C3, C4 Photosynthesis, and CAM

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C 3, C 4 and CAM plants

C 3, C 4 and CAM plants. Introduction C 3, C 4 and CAM photosynthesis are the three types of photosynthesis in green plants. C 3 photosynthesis is the. Presentation on theme: "C 3, C 4 and CAM plants. Introduction C 3, C 4 and CAM photosynthesis are the three types of photosynthesis in green plants. C 3 photosynthesis is the."— Presentation transcript:

2 Introduction C 3, C 4 and CAM photosynthesis are the three types of photosynthesis in green plants. C 3 photosynthesis is the photosynthesis we have learned about in class. C 4 and CAM photosynthesis are adaptations to arid conditions.

3 C 3 Photosynthesis C 3 is so called because the first compound made when carbon dioxide is fixed from the atmosphere has three carbons (PGAL). Stomata are open during the day. RuBisco is the enzyme involved in carbon fixation.

4 C 3 Photosynthesis Photosynthesis takes place throughout the leaf. Most plants are C3 because it requires fewer enzymes and less specialized machinery than C4 and CAM photosynthesis. It is the most efficient form of photosynthesis under normal light intensity, lower temperature and normal moisture.

5 C 4 Photosynthesis Called C 4 because carbon dioxide is fixed into a four carbon compound. Stomata open during the day. Dark Reactions take place in inner cells called Kranz Anatomy.

6 C 4 Photosynthesis Uses the enzyme PEP carboxylase to fix carbon dioxide into a four carbon compound (usually malic acid) and then delivers it to RuBisCO to provide carbon dioxide and continue photosynthesis similar to the C 3 pathway.

7 C 4 Photosynthesis This works faster than C 3 photosynthesis under high light intensity and high temperature because it delivers CO 2 directly to RuBisCO thereby maximizing carbohydrate formation and preventing product loss due to photorespiration.

8 Photorespiration Definition Photorespiration is a process in plant metabolism by which RuBP (a sugar) has oxygen added to it by RuBisCO, instead of carbon dioxide during normal photosynthesis. This process reduces efficiency of photosynthesis in C3 plants. Oxygen acts as a competitive inhibitor.

9 C 4 Photosynthesis It is also more efficient in terms of water use because PEP carboxylase brings in CO 2 faster and therefore does not need to keep the stomata open for as long, thereby minimizing water loss. C 4 photosynthesis is common in plants that grow mainly during the intense heat of summer in North America (i.e. Corn).

10 CAM Photosynthesis Crassulacean acid metabolism CAM) photosynthesis is another adaptation for plants that are in arid conditions. Stomata are closed during the day and open at night to reduce water loss through transpiration.

11 CAM Photosynthesis These plants fix carbon dioxide into vacuoles during the night and incorporate it into malic acid similar to the C4 pathway. During the day, the malic acid transfers carbon dioxide to RuBisCO and carbohydrate is made.

12 CAM Photosynthesis CAM plants often have thick, reduced leaves with a low SA to V ratio; thick cuticle; and stomata sunken into pits. Some store water in vacuoles (succulent plants). CAM plants can also be recognized as plants whose leaves have an increasing sour taste during the night yet become sweeter-tasting during the day. This is due to malic acid stored in the vacuoles of the plants' cells during the night and then used up during the day. That is why we let pineapple ripen before eating!

13 CAM Photosynthesis CAM plants can “CAM-idle” which allows them to keep their stomata closed at all times during extremely arid conditions and therefore any oxygen they give off in photosynthesis is immediately used in cellular respiration and vice versa. This allows the plant to survive dry periods and recover very quickly when water returns.

14 CAM vs. C 4 Photosynthesis Similarities Differences Both are a response to arid conditions. Both use water more efficiently than C3 plants. Both minimize the amount of photorespiration by proving carbon dioxide directly to RuBisCO. CAM plants provide CO 2 temporally (stockpile it at night and provide it during the day) whereas C4 plants provide CO 2 spatially (take it from the outer cells and provide it to the inner Kranz Anatomy). C4 plants require special Krantz Anatomy. C4 plants have stomata open during the day while CAM plants have stomata open at night.

C4 Photosynthesis in Plants

Types of Photosynthesis: II. C4 Photosynthesis

C4 Photosynthesis. This mechanism of photosynthesis occurs in two adjoining types of cells, the mesophyll and bundle sheath cells in plant species called C4 plants. Both C3 and C4 cycles operate in the non-light-requiring or Dark Reactions of photosynthesis but spatially. that is, in different cells: C4 in the mesophyll cells immediately followed by C3 cycle in the bundle sheath cells.

CO2 first enters the leaf and into the mesophyll cell. It is then hydrated to produce bicarbonate ion (HCO3-) in the cytoplasm  with carbonic anhydrase (CA ) as catalyst. This is the first step in C4 photosynthesis, followed by carboxylation reaction utilizing HCO3- instead of CO2 as the inorganic carbon substrate, Hatch and Burnell (1990) emphasized.

HCO3- reacts  with the three-carbon acid phosphoenolpyruvate (PEP or PEPA, C3H5O6P) to form oxaloacetate (OAA. oxaloacetic acid= C4H4O5). The reaction is catalyzed by the carboxylating enzyme phosphoenolpyruvate carboxylase (PEPcase. PEPC or PEPCO). OAA is a four-carbon product, hence the term C4 photosynthesis.

(1) Hydration of CO2 (catalyzing enzyme is carbonic anhydrase):

(2) Carboxylation of HCO3- (catalyzing enzyme is PEPcase):

                   HCO3- + PEP ---------->OAA

The summary reaction is commonly written as shown below in which the hydration reactions leading to the formation of HCO3- and its carboxylation are skipped :

OAA is then reduced to malate (malic acid= C4H6O5) or transaminated to aspartate (aspartic acid= C4H7NO4) and transported to the adjacent bundle-sheath cells. As to malate, it is utilized in two ways: for the regeneration of PEP, and for the supply of CO2 for the succeeding C3 cycle. First, malate is decarboxylated in which CO2 is removed and pyruvate (pyruvic acid= C3H4O3) is formed. Pyruvate goes back to the mesophyll cell where it is phosphorylated to PEP, the CO2 acceptor in the C4 cycle. The freed CO2 enters the C3 cycle within the bundle sheath cell.

As in C3 photosynthesis, the product of the biochemical reactions in the bundle sheath cells is the three-carbon sugar glyceraldehyde-3-phosphate (G3P. C3H7O6P), also called  triose phosphate and phosphoglyceraldehyde (PGAL). Similarly, some molecules of G3P undergo reactions to regenerate RuBP, the CO2 acceptor in the C3 cycle. Other molecules of G3P  leave the cycle and proceed with the formation of glucose and other organic compounds that plants need.

Contrasted to C3 photosynthesis, the C4 photosynthetic pathway is more efficient based on resistance to photorespiration which is a wasteful process. Unlike in C3 photosynthesis, the initial CO2-fixing enzyme PEPcase in C4 cycle does not act as oxygenase and therefore it does not fix O2 even when it is in high concentration within the cell. This enzyme initially fixes atmospheric CO2 in the mesophyll cells which is then delivered to the bundle sheath cells in the form of organic acids.

The C4 cycle in C4 photosynthesis therefore serves as a CO2-concentrating mechanism  for the bundle sheath cells. The high concentration of CO2 favors the fixing of CO2, instead of O2, by rubisco. Photorespiration is thus suppressed.

However, the C4 pathway of CO2 reduction expends more energy (5 ATP and 2 NADPH) than C3 pathway (3 ATP and 2 NADPH) (Hopkins 1999). Nevertheless, the former is efficient under conditions of high light intensity, high temperature, and limited water.

(Ben G. Bareja Aug. 2013)

Photosynthesis III - C3, C4, and CAM photosynthesis

BI 203 - Study Guide for Final Exam

In addition to the material below, you should also be familiar with the material from the previous two study guides because the final is cumulative.

C3, C4, and CAM photosynthesis

What is photorespiration? How does it differ from dark respiration? What is the cost of photorespiration to the plant? Why does it happen? What conditions lead to higher rates of photorespiration?

How does the C4 pathway solve problems of photorespiration? What is the role of the Calvin cycle in C4 photosynthesis? What is the primary enzyme, the precursors, the products and the cost of the C4 pathway? Is this a cycle? What is Kranz anatomy? Why don�t all plants have C4 photosynthesis? In what regions is C4 particularly important? Why?

How is CAM photosynthesis similar to and different from both C3 and C4? What are the advantages and disadvantages of each?

Water in plants

Reading: pp. 76-81, Chap.31

What are the components of the full water potential equation? How does each affect the free energy and movement of water - between cells, and between plant and soil?

What is transpiration and why is it a "necessary evil"? How important is transpirational water loss in the whole water budget of a plant? Why can�t capillarity and air pressure account for transpirational movement of water through plants? How does water potential and the tension-cohesion mechanism account for this movement? What is the water potential gradient through a plant?

What factors, both biotic and abiotic control rates of transpiration?

What components of water potential account for night-time root pressure in some plants? What is guttation? What is hydraulic lift and how does it work? How does it relate to water potential and water potential gradients? What are some ecological consequences of hydraulic lift?

What moves through phloem? What is meant by "source-sink" relationships in phloem flow? How does phloem flow differ from xylem flow? What is the pressure flow hypothesis and the three main steps involved? How does each step work?

Reading: Chap. 30, pp. 726-731, 736-742

What is an "essential element"? What is the difference between macronutrients and micronutrients? Who are the macronutrients, where do they come from, and what is at least one major function of each?

What two factors contribute to the deficiency symptoms for the different nutrients? Which macronutrients have high, intermediate and low mobility?

Why is nitrogen important to plants? In what forms is N available to plants in soils? What steps are important in plant assimilation of nitrogen and how does this differ among the different available forms?

What are the main steps of the nitrogen cycle? what are the main pools and fluxes? What organisms mediate the different steps? Why is N-fixation important to the nitrogen cycle?

What happens in the process of N-fixation? Who does it? What is the mutualistic tradeoff in symbiotic N-fixation? How specific is this process? What are the steps in nodule formation? What factors potentially constrain N-fixation and how does the plant solve the oxygen problem?

Reading: Chap. 28 to p.693

What is the definition of a hormone? What factors control the expression of a hormone-induced response? What is signal transduction pathway and what is at least one example from the hormones that we studied?

What is the primary natural auxin? Where is it made and how is it transported? What are the effects of auxin and how do they work? What is an experiment that demonstrates the role of auxin in apical dominance? What auxin mimics are important and why?

What are cytokinins, where are they made, and what are their effects? How do they interact with IAA? How were cytokinins discovered and how are they used today? What is totipotency?

What are giberellins, where are they made and what are their functions? How do they interact with the aleurone layer in monocot seeds?

What is unique about ethylene? What is its structure and what are its effects? What is a climacteric fruit and some examples of that type of fruit? How is ethylene used commercially now? How has this use contributed (indirectly) to the downfall of tomato flavor?

How does abscisic acid (ABA) affect stomatal closure?

Plant response to the environment

Reading: chap. 29, pp. 702-714.

What is a positive tropism and what is a negative tropism? How does gravitopism work in roots and shoots? How is the mechanism and response similar and how different in these different tissues? What is phototropism and what is its mechanism of action?

What are the different photoperiod plant types? What role does phytochrome play in photoperiod sensation? What is phytochrome's sensitivity to different wavelengths of light? How does a plant measure the length of a dark cycle? How do we know these things from studies of seed germination and flowering?

What other roles does phytochrome play in etiolation and growth responses in shade? How might these be ecologically important to a plant?

Plant Life: C4 and CAM Photosynthesis

Alternative forms of photosynthesis are used by specific types of plants, called C4 and CAM plants, to alleviate problems of photorespiration and excess water loss.

Photosynthesis is the physiological process whereby plants use the sun’s radiant energy to produce organic molecules. The backbone of all such organic compounds is a skeleton composed of carbon atoms. Plants use carbon dioxide from the atmosphere as their carbon source.

The overwhelming majority of plants use a single chemical reaction to attach carbon dioxide from the atmosphere onto an organic compound, a process referred to as carbon fixation. This process takes place inside specialized structures within the cells of green plants known as chloroplasts.

The enzyme that catalyzes this fixation is ribulose bisphosphate carboxylase (Rubisco), and the first stable organic product is a three-carbon molecule. This three-carbon compound is involved in the biochemical pathway known as the Calvin cycle. Plants using carbon fixation are referred to as C3 plants because the first product made with carbon dioxide is a three-carbon molecule.

For many years scientists thought that the only way photosynthesis occurred was through C3 photosynthesis. In the early 1960’s, however, researchers studying the sugarcane plant discovered a biochemical pathway that involved incorporation of carbon dioxide into organic products at two different stages.

First, carbon dioxide from the atmosphere enters the sugarcane leaf, and fixation is accomplished by the enzyme phosphoenolpyruvate carboxylase (PEP carboxylase). This step takes place within the cytoplasm, not inside the chloroplasts. The first stable product is a four-carbon organic compound that is an acid, usually malate. Sugarcane and other plants with this photosynthetic pathway are known as C plants.

In C4 plants, this photosynthetic pathway is tied to a unique leaf anatomy known as Kranz anatomy. This term refers to the fact that in C4 plants the cells that surround the water- and carbohydrate conducting system (known as the vascular system) are packed very tightly together and are called bundle sheath cells.

Surrounding the bundle sheath is a densely packed layer of mesophyll cells. The densely packed mesophyll cells are in contact with air spaces in the leaf. and because of their dense packing they keep the bundle sheath cells from contact with air. This Kranz anatomy plays a major role in C4 photosynthesis.

In C4 plants the initial fixation of carbon dioxide from the atmosphere takes place in the densely packed mesophyll cells. After the carbon dioxide is fixed into a four-carbon organic acid, the malate is transferred through tiny tubes from these cells to the specialized bundle sheath cells.

Inside the bundle sheath cells, the malate is chemically broken down into a smaller organic molecule, and carbon dioxide is released. This carbon dioxide then enters the chloroplast of the bundle sheath cell and is fixed a second timewith the enzyme Rubisco and continues through the C3 pathway.

Advantages of Double-Carbon Fixation

The double-carbon fixation pathway confers a greater photosynthetic efficiency on C4 plants over C3 plants, because the C3 enzyme Rubisco is highly inefficient in the presence of elevated levels of oxygen. In order for the enzyme to operate, carbon dioxide must first attach to the enzyme at a particular location known as the active site.

However, oxygen is also able to attach to this active site and prevent carbon dioxide from attaching, a process known as photorespiration. As a consequence, there is an ongoing competition between these two gases for attachment at the active site of the Rubisco enzyme. Not only does the oxygen outcompete carbon dioxide; when oxygen binds to Rubisco, it also destroys some of the molecules in the Calvin

At any given time, the winner of this competition is largely dictated by the relative concentrations of these two gases. When a plant opens its stomata (the pores in its leaves), the air that diffuses in will be at equilibrium with the atmosphere, which is 21 percent oxygen and 0.04 percent carbon dioxide.

During hot, dry weather, excess water vapor diffuses out, and under these conditions plants face certain desiccation if the stomata are left open continuously.When these pores are closed, the concentration of gases will change. As photosynthesis proceeds, carbon dioxide will be consumed and oxygen generated.

When the concentration of carbon dioxide drops below 0.01 percent, oxygen will outcompete carbon dioxide at the active site, and no net photosynthesis occurs. C4 plants, however, are able to prevent photorespiration, because the PEP carboxylase enzyme is not inhibited by oxygen.

Thus, when the stomata are closed, this enzyme continues to fix carbon inside the leaf until it is consumed. Because the bundle sheath is isolated from the leaf’s air spaces, it is not affected by the rising oxygen levels, and the C3 cycle functions without interference. C4 photosynthesis is found in at least nineteen families of flowering plants.

No family is exclusively composed of C4 plants. Because C4 photosynthesis is an adaptation to hot, dry environments, especially climates found in tropical regions, C4 plants are often able to out compete C3 plants in those areas. In more temperate regions, they have less of an advantage and are therefore less common.

A second alternative photosynthetic pathway, known as crassulacean acid metabolism (CAM), exists in succulents such as cacti and other desert plants. These plants have the same two carbon-fixing steps as are present in C4 plants, but rather than being spatially separated between the mesophyll and bundle sheath cells, CAM plants have both carbon dioxide-fixing enzymes within the same cell.

These enzymes are active at different times, PEP carboxylase during the day and Rubisco at night. Just as Kranz anatomy is unique to C4 plants, CAM plants are unique in that the stomata are open at night and largely closed during the day.

The biochemical pathway of photosynthesis in CAM plants begins at night. With the stomata open, carbon dioxide diffuses into the leaf and into mesophyll cells, where it is fixed by the C4 enzyme PEP carboxylase. The product is malate, as in C4 photosynthesis, but it is transformed into malic acid (a nonionic form of malate) and is stored in the cell’s vacuoles (cavities within the cytoplasm) until the next day.

Although the malic acid will be used as a carbon dioxide source for the C3 cycle, just as in C4 photosynthesis, it is stored until daylight because the C3 cycle requires light as an energy source. The vacuoles will accumulate malic acid through most of the night.

A few hours before daylight, the vacuole will fill up, and malic acid will begin to accumulate in the cytoplasm outside the vacuole. As it does, the pH of the cytoplasm will become acidic, causing the enzyme to stop functioning for the rest of the night.

When the sun rises the stomata will close, and photosynthesis by the C3 cycle will quickly deplete the atmosphere within the leaf of all carbon dioxide. At this time, the malic acid will be transported out of the vacuole to the cytoplasmof the cell. There it will be broken down, and the carbon dioxide will enter the chloroplast and be used by the C3 cycle; thus, photosynthesis is able to continue with closed stomata.

Crassulacean acid metabolism derives its name from the fact that it involves a daily fluctuation in the level of acid within the plant and that it was first discovered to be common in species within the stonecrop family, Crassulaceae.

The discovery of this photosynthetic pathway dates back to the 1960’s. The observation that succulent plants become very acidic at night, however, dates back to at least the seventeenth century, when it was noted that cactus tastes sour in the morning and bitter in the afternoon.

CAM Plant Ecosystems

There are two distinctly different ecological environments where CAM plants may be found. Most are terrestrial plants typical of deserts or other harsh, dry sites.

In these environments, the pattern of stomatal opening and closing provides an important advantage for surviving arid conditions: When the stomata are open, water is lost; however, the rate of loss decreases as the air temperature decreases. By restricting the time period of stomatal opening to the nighttime, CAM plants are extremely good at conserving water.

The other ecological setting where CAM plants are found is in certain aquatic habitats. When this environment was first discovered, it seemed quite odd, because in these environments conserving water would be of little value to a plant. It was found, however, that there are aspects of the aquatic environment which make CAM photosynthesis advantageous.

In shallow bodies of water, the photosynthetic consumption of carbon dioxide may proceed at a rate in excess of the rate of diffusion of carbon dioxide from the atmosphere into the water, largely because gases diffuse several times more slowly in water than in air.

Consequently, pools of water may be completely without carbon dioxide for large parts of the day. Overnight, carbon dioxide is replenished, and aquatic CAM plants take advantage of this condition to fix the plentiful supply of carbon dioxide available at night and store it as malic acid.

Hence, during the day, when the ambient carbon dioxide concentration is zero, these plants have their own internal supply of carbon dioxide for photosynthesis. Thus, two very different ecological conditions have selected for the identical biochemical pathway.

These two modified photosynthetic pathways adequately describe what happens in most terrestrial plants, although there is much variation. For example, there are species that appear in many respects to have photosynthetic characteristics intermediate to C3 and C4 plants.

Other plants are capable of switching from exclusively C3 photosynthesis to CAM photosynthesis at different times of the year. Photosynthesis by aquatic plants appears to present even more variation. C3-C4 intermediate plants seem to be relatively common compared to the terrestrial flora. and several species have C4 photosynthesis but lack Kranz anatomy.