ArtsAutosBooksBusinessEducationEntertainmentFamilyFashionFoodGamesGenderHealthHolidaysHomeHubPagesPersonal FinancePetsPoliticsReligionSportsTechnologyTravel

Photosynthesis Experiment in Elodea in Direct Light, Distant Light, and Dark

Updated on December 4, 2016


In 1905 an English plant physiologist by the name of F.F. Blackmen found that increased light caused an increase in photosynthesis.

He broke photosynthesis into the light reactions, or a light-dependent phase, and the dark reactions, or carbon dioxide fixation.

The light dependent phase of photosynthesis is when a photon (a light energy unit) is needed to excite two electrons in chlorophyll that eventually breaks down a water molecule which creates ATP from ADP and forms NADPH2 from NADPH. This process is called photophoshphorylation.

Photophosphorylation is broken down into two types. One type is called cyclic photophosphorylation which refers to the excitation of electrons between the different pigments in the thylakoids.

The second type in non-cyclic photophosphorylation refers to the breaking down of a water molecule.

A collection of the different pigment types, mainly chlorophyll a, chlorophyll b, and carotenoids, used during photophosphorylation is called a photosystem.

There are three different photosystems used during photophosphorylation. The reactive pigment in each photosystem is called the reaction center while the others are called antenna pigments.

In photosystem II of non-cyclic photophosphorylation, the two electrons cause the water molecule to split forming two H+, and free oxygen that will combine with another oxygen to form an oxygen molecule. At this point 2ATP is created by the breakdown and NADPH grabs the free H+.

In 1938 Ruben and Kamen tagged both water and carbon dioxide molecules with oxygen-18. One plant was grown in the tagged water and another was fed the tagged carbon dioxide.

The plant that was grown in the tagged water produced a larger number of oxygen molecules with oxygen-18 than the plant fed the tagged carbon dioxide.

This experiment was able to show that the water molecule provided the oxygen molecules that are released into the atmosphere, thus carbon dioxide is primarily used in the formation of carbohydrates.

After the water molecule is broken down one H+ enters the respiratory chain and is reunited with oxygen during the final cytochrome oxidase step to recreate another water molecule. This process produces 3ATP.

The other H+ combines with the carbon dioxide to form carbohydrate. This process, called carbon dioxide fixation or the dark reaction, requires the ATP that was created during the respiratory chain.

There are many byproducts of photosynthesis including organic phosphates, amno acids, and organic acids. Some of the sugar phosphate compound byproducts are used to produce sucrose, starch, and cellulose.

Sugars are extremely soluble in water and can cause osmotic balance problems. To avoid this problem plants convert sugars into starch within the chloroplasts. Starch is then broken down again when glucose is needed for cellular metabolism.

In the Calvin-Benson pathway, carbon dioxide eventually anabolises into a 5-carbon sugar with 2 phosphates or "ribose-1.5-diphosphate." The 5-carbon sugar then splits into two 3-carbon compounds called phosphoglyceric acid (PGA) which, after the addition of H+, eventually becomes a starch.

The Hatch-Slack pathway is similar, yet a 4-carbon splits to form oxaloacetic acid.

The purpose of observing the change in oxygen production by Elodea when placed in direct white light, indirect white light, and darkness is to show how light is necessary to excite electrons and start photophosphorylation.

Elodea Cells
Elodea Cells

Materials and Methods

A YUS-190-M Photosynthesis Apparatus was clamped horizontally onto a stand. A leafy shoot of Elodea was cut and the cut end was placed inside a clear plastic tube located on the lower right corner of the apparatus.

The Elodea was then placed into a beaker with a 0.05% potassium bicarbonate solution. The solution was drawn through the apparatus by using syringes located on the upper left hand corner of the apparatus.

Once the Elodea formed a bubble of oxygen in the clear plastic tubing, the bubble was drawn into the measuring capillary located within the apparatus and measured. All the air bubbles produced were measured within one minute, and the sum of all the measurements within a minute was reported as mm/min.

These measurements were repeated, every five minutes with a close light source, a distant light source, and darkness.

Each situation was repeated, with different Elodea, three time and averaged.


There was a variance in the amount of oxygen produced in the averaged values of the three Elodea.

The first Elodea produced 1.46 mm/min of oxygen in the presence of close white light while the second Elodea produced 2.65 mm/min and the third produced 4 mm/min.

In distanced light the first Elodea produced 1.45 mm/min, the second 1.28 mm/min, and the third 1.5 mm/min.

In darkness, the first Elodea produced 0.052 mm/min, the second 0.128 mm/min, and the third 1.5 mm/min.

Elodea produced approximately 90% less oxygen in darkness then light, and approximately 45% less oxygen in distant light.


It is obvious that there is a significant difference in the percentage of oxygen produced in the Elodea between the dark and light environments.

This shows that the largest percentage of oxygen is produced in the light dependent phase of photosynthesis. Light is needed to excite the two electrons in cyclic photophosporylation in photosystem I to break down the water molecule in non-cyclic photophosphorylation and donate the oxygen necessary to create oxygen molecules that are released into our atmosphere.

This experiment also shows that a small percentage of oxygen is produced during the dark reaction, or the carbon fixation stage, when the carbon dioxide combines with H+ to form carbohydrates.


    0 of 8192 characters used
    Post Comment
    • jhamann profile imageAUTHOR

      Jamie Lee Hamann 

      7 years ago from Reno NV

      Thank you phdast7. Jamie

    • phdast7 profile image

      Theresa Ast 

      7 years ago from Atlanta, Georgia

      Wow Jaimie - If you had been my Biology teacher, maybe I wouldn't have disliked it so much. :) Very interesting and fairly understandable (if I read slowly) considering that I am a Humanities, not a Sciences person. Good graphics, too. Hope all is well with you. Sharing.

    • jhamann profile imageAUTHOR

      Jamie Lee Hamann 

      7 years ago from Reno NV

      Thank you ignugent17. Jamie

    • profile image


      7 years ago

      Thanks for sharing your expirements. Elodea is new to me. Additional word in my vocabulary.

      Voted up and interesting. :-)

    • jhamann profile imageAUTHOR

      Jamie Lee Hamann 

      7 years ago from Reno NV

      Thank you Eddy for your comment. Jamie

    • Eiddwen profile image


      7 years ago from Wales

      This is so interesting and well informed. Great work

      Enjoy your weekend.


    • jhamann profile imageAUTHOR

      Jamie Lee Hamann 

      7 years ago from Reno NV

      Thank you tobusiness. Jamie

    • tobusiness profile image

      Jo Alexis-Hagues 

      7 years ago from Lincolnshire, U.K

      Very informative article. Well done.

    • jhamann profile imageAUTHOR

      Jamie Lee Hamann 

      7 years ago from Reno NV

      Thank you Audrey, Mhatter99 (i will stop by soon), and Vellur for stopping by. I hope your day goes well. Jamie

    • Vellur profile image

      Nithya Venkat 

      7 years ago from Dubai

      Very useful. An interesting experiment with results that makes us put our thinking cap on. Voted up, crystal clear write up,pinned.

    • Mhatter99 profile image

      Martin Kloess 

      7 years ago from San Francisco

      Took me back to biology, but that would be a hub in itself, All good, my friend. Don't miss the reggae in today's poem. Thank you.

    • AudreyHowitt profile image

      Audrey Howitt 

      7 years ago from California

      Ah! Somehow I missed that about you! Makes sense! I should hook you up with a poet scientist friend of mine--skinless Frank on think you'd like him---look up his work---it is a goood community

    • jhamann profile imageAUTHOR

      Jamie Lee Hamann 

      7 years ago from Reno NV

      Thank you Audrey, by training. Jamie

    • AudreyHowitt profile image

      Audrey Howitt 

      7 years ago from California

      What a great article Jamie--are you a scientist by inclination?


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
    ClickscoThis is a data management platform studying reader behavior (Privacy Policy)