Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.
Kermit the Frog once said, 'it's not easy being green.' Now, he may not have been talking about plants, but he might as well have because plants must overcome numerous challenges in order to make their own food, survive and thrive in hostile environments.
There are thousands of different types of plants, but only three different ways in which they can undergo photosynthesis, or taking carbon dioxide from the air, water from their roots, and sunlight and transforming it into sugar and oxygen.
Carbon dioxide is a molecule made up of a carbon and two oxygen atoms, but it may be more familiar to you as the molecule that comes out of your mouth every time you exhale! It's pretty amazing that plants can make their own food out of that stuff, isn't it?
Here are the three types of plants, each undergoing a slightly different type of photosynthesis:
- C3 plants are the most common and the most efficient at photosynthesis in cool, wet climates.
- C4 plants are most efficient at photosynthesis in hot, sunny climates.
- CAM plants are adapted to avoid water loss during photosynthesis so they are best in deserts.
Before we can fully understand each type of plant, we need some background information.
The Calvin Cycle
Have you ever wondered how plants turn carbon dioxide, water and sunlight into sugar? The Calvin cycle is part of this process and, in order to understand C3 plants, you need a brief lesson in the Calvin cycle:
- Carbon dioxide enters through the tiny pores on a plant's leaf called stomata (or stoma if it's just one). Sometimes the C3 plant accidentally takes in oxygen, too, which can slow down the process.
- This carbon dioxide then combines with a sugar with the help of an enzyme called RuBisCO. An enzyme is a substance that helps reactions move along faster.
- This sugar-carbon dioxide combination eventually becomes a molecule made up of three carbon atoms, and that is where C3 plants get their name. For C3 plants, this process takes place in a chloroplast, the green cells in plants that help with photosynthesis. These are what make a plant green!
- The cycle continues and, with the help of energy from the sun, sugar is made as well as more RuBisCO for future use.
Three Types of Photosynthesis
In order to understand why certain plants do better in certain environments, let's take a look at each type of plant. Note: C3 plants undergo C3 photosynthesis, C4 plants undergo C4 photosynthesis and CAM plants undergo CAM photosynthesis.
These types of plants, as mentioned earlier, do better in cooler, wetter climates. They keep their stomata open during the day. In hot, dry areas, it is dangerous to leave stomata open during the day because the plants lose water through the stomata. The Calvin cycle takes place in the chloroplast for C3 plants.
Most plants are C3 plants and some examples include: evergreen trees, deciduous trees and weedy plants like lambs quarters and bindweed. Important crop plants like rice, barley and soybean are also C3. Many plants that live in the tropics and subtropics, where precipitation is not sparse, are C3 plants.
Do you remember where C3 plants got their name? Well C4 plants get their name because in their cycle, a molecule made up of four carbon atoms is made but we won't go into too much into that process because our focus is on the C3 plant. Although they have their stomata open during the day like C3 plants, C4 plants are able to close them more often to avoid water loss.
Examples of C4 plants include: corn, nutgrass, and tumbleweed. Less than three percent of all plants are C4 plants.
This stands for Crassulacean acid metabolism. It gets its name because Crassulaceae are the first plants this type of photosynthesis was discovered in and CAM plants turn their carbon dioxide into acid. This is done so the plant can store the carbon dioxide and use it at night when the stomata are open. By keeping the stomata closed during the day, the plant minimizes water loss.
Examples of CAM plants: many succulent plants like the popular jade and aloe houseplants. Also included in this group is the pineapple.
Approximately 85% of plants use C3 photosynthesis, which is the most effective in cool, wet habitats. C3 plants do not need to worry about losing water, so they can keep their stomata open for long periods of time during the day. C3 plants go through the Calvin cycle, taking in carbon dioxide through the leaves' minuscule pores, called stomata. An enzyme called RuBisCO helps the carbon dioxide combine with sugar. Eventually, the sugar and carbon dioxide form a molecule with three carbon atoms (C3) in the chloroplast. You've probably encountered numerous C3 plants today - you might have walked across a lawn of grasses, stood underneath a deciduous tree or even eaten a meal of rice with spinach and beets.
When you are finished, you should be able to:
- Name the three groups of plants that perform a type of photosynthesis
- Enumerate the steps in the Calvin cycle
- Outline the three types of photosynthesis
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