Light wavelength and photosynthetic rate relationship

light wavelength and photosynthetic rate relationship

Research Question: How does the wavelength of light affect the rate of photosynthesis (mg/L/minute) of Elodea, by measuring the oxygen. This is because red light wavelengths which are absorbed by the leaves of the plant The Effect Of Light Intensity On Rate Of Photosynthesis. The relationship between pigmentation and growth in different light qualities is not The oxygen electrode carried out determination of the photosynthetic rate.

Photosynthesis increases as you increase the light intensity from darkness. Where these two curves intersect, the rate of photosynthesis, measured as oxygen produced, matches the rate of respiration, measured as oxygen consumed. Obviously one could measure the reactions by carbon dioxide or sugar, etc.

The light intensity in whatever units used where these curves intersect is called the compensation point. When plants are kept at intensities above the compensation point, they are doing photosynthesis faster than they are using up the products in respiration.

light wavelength and photosynthetic rate relationship

So at these higher intensities, the plant can add to its reserves, can grow, or can reproduce. However, whenever a plant is at intensities below the compensation point, it is burning up photosynthate faster than it is being produced.

light wavelength and photosynthetic rate relationship

Kept here for any length of time it will be using up its reserves, and may even die. In the graph above, the plant has a compensation point that is below that found in most rooms of a house; such a plant is likely a potential houseplant. Ferns and African violets may be among these.

Not every plant has the same compensation point, as you might expect! Indeed in the figure below, two plant responses to light intensity are shown. The assumption made in the figure is that the rate of respiration in both plant A and plant B are the same this may not be a valid assumption!

You will notice that plant B is far less efficient in photosynthesis; it takes much more light to reach its compensation point. Plant B is likely a crop plant such as corn or soybeans; they would never make it as houseplants. You might also notice how houseplants "burn up" their photosystems bleach out! Light also has particle properties: These "packets" of light are called photons. In fact in plant physiology we usuallly measure light intensity as photon flux density PFD measured in units of photons m-2 s If photosynthesis were to be completely efficient, the production of an oxygen molecule in photosynthesis theoretically requires just four protons and four electrons.

However, in actual measurements, the quantum efficiency observed is about 10 photons per oxygen molecule. This is shown in the classic quantum efficiency plot of Emerson and Arnold: This plot also shows that up to chlorophyll molecules can be involved in producing this oxygen molecule. At the time of Emerson, this seemed troubling but now we know that the light harvesting complex for the two photosysytems each contain a few hundred chlorophylls, and they both must operate four times to make the oxygen molecule.

The quantum yield is the slope on this curve and this works out to 10 photons needed to make one molecule of oxygen.


A wide range of wavelengths drive photosynthesis Emerson went on to study the effect of wavelength on photosynthesis. This kind of plot is sometimes called an "action spectrum", it shows how effectively various wavelengths drive photosynthesis.

Superimposed on this plot we see the quantum yield as a function of wavelenth of the photons. In both sets of curves, you can see that photons of green wavelength are less efficient than those in blue and red wavelengths. Photons with wavelength beyond lack sufficient energy to drive photosynthesis!

Recall that blue wavelengths have higher energy than red wavelengths.

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This fact tells us that whatever pigments are involved in photosynthesis, they apparently have a minimum energy required to excite an electron that is found in a red photon. You can see that all but a few wavelengths between and nm are fairly effective for photosynthesis.

The lower yield for the nm green range of the spectrum explains the green color of plants. These wavelengths are reflected and transmitted rather than being as effective in driving the process. The absorption spectrum shown is for a chloroplast, obviously antenna pigments are at work here.

What is critical to notice is the huge drop in efficiency at nm; this is known as the "red drop" effect.

Wavelength of light affect on the rate of photosynthesis of by Farah Addam on Prezi

Wavelengths beyond nm are apparently of insufficient energy to drive any part of photosynthesis. A longer wavelength is associated with lower energy and a shorter wavelength is associated with higher energy.

The types of radiation on the spectrum, from longest wavelength to shortest, are: Visible light is composed of different colors, each having a different wavelength and energy level. The colors, from longest wavelength to shortest, are: It includes electromagnetic radiation whose wavelength is between about nm and nm.

You can see these different colors when white light passes through a prism: Red light has the longest wavelength and the least energy, while violet light has the shortest wavelength and the most energy.

Although light and other forms of electromagnetic radiation act as waves under many conditions, they can behave as particles under others. Each particle of electromagnetic radiation, called a photon, has certain amount of energy.

light wavelength and photosynthetic rate relationship

Types of radiation with short wavelengths have high-energy photons, whereas types of radiation with long wavelengths have low-energy photons. However, the various wavelengths in sunlight are not all used equally in photosynthesis. Instead, photosynthetic organisms contain light-absorbing molecules called pigments that absorb only specific wavelengths of visible light, while reflecting others.

The set of wavelengths absorbed by a pigment is its absorption spectrum. In the diagram below, you can see the absorption spectra of three key pigments in photosynthesis: The set of wavelengths that a pigment doesn't absorb are reflected, and the reflected light is what we see as color.

light wavelength and photosynthetic rate relationship

High intensity blue LEDs promote plant growth by controlling the integrity of chloroplast proteins that optimize photosynthetic performance in the natural environment.

Introduction Plants use light as an energy source for photosynthesis and as an environmental signal, and respond to its intensity, wavelength, and direction.

Light and photosynthetic pigments

Light is perceived by plant photoreceptors that include phytochromes, cryptochromes and phototropins and plants generate a wide range of specific physiological responses through these receptors. A major challenge to plants is controlled by supplying sufficient quantity and quality of light intensities [ 12 ].

Light emitting diodes LEDs has been proposed as a light source for controlled environment agriculture facilities and space based plant growth chambers because they exhibit desirable characteristics such as small mass, safety and durability [ 3 — 5 ]. Plant development and physiology are strongly influenced by the light spectrum of the growth environment among which blue light is involved in a wide range of plant processes such as phototropism, photo-morphogenesis, stomatal opening, and leaf photosynthetic functioning [ 6 ].

Most studies assessing the effects of blue light blue LEDs on the leaf or whole plant have either compared the response to a broadband light source with response to blue deficient light [ 7 ] or compared plants grown under red light alone [ 58 ].