Light Quality on the Rate of Photosynthesis Measure Sample Essay


This survey was undertaken to find the relationship of different wavelengths of visible radiation and the rate of photosynthesis in Spinacia oleracea foliage. The rate of photosynthesis was measured every five min under light colourss of white. green. ruddy. blue and xanthous under a light strength of 2000 lx. The rate of photosynthesis was measured by the Spinacia oleracea disc method in which we replaced the air from the discs with Na hydrogen carbonate utilizing a vacuity. Under photosynthesis. O. a merchandise of photosynthesis. replaced the bicarbonate solution. made the discs less dense and rise to the top. The rate of photosynthesis was the greatest under white visible radiation. followed by ruddy. blue. xanthous and green. which produced no noticeable photosynthesis meaning that chlorophyll reflects. instead than absorbs. green visible radiation. White visible radiation was besides expected to hold the highest rate of photosynthesis as it gives the chlorophyll all the colourss of visible radiation to absorb. In general. filtered visible radiation reduced the rate of photosynthesis because the chlorophyll didn’t receive all the different colourss of the spectrum it desired as it did in white visible radiation to absorb.


Photosynthesis is the ability to change over light energy into chemical energy in the signifier of sugar ( Freeman 2002 ) . The photosynthetic reactions are divided into two subdivisions: light dependant and light independent reactions. In this experiment. we will be covering with the light dependent reactions. The existent chemical science of the light dependent reaction is with the add-on of visible radiation: H2O + ADP + inorganic phosphate + NADP+ ? 1/2O2 + ATP + NADPH + H.

Light is a necessary input for photosynthesis to take topographic point. Light’s electromagnetic radiation carried in photons are absorbed by the photosynthetic pigments in workss. These photons can do electron excitement to a higher energy degree. which can be added to NADP+ signifier NADPH or the aroused negatrons can besides be passed down an negatron conveyance concatenation bring forthing ATP. These procedures occur in photosystem I and photosystem II severally. The splitting of H2O into negatrons and O occurs in photosystem II. We can mensurate the rate of photosynthesis by mensurating the sum of O. because O is a merchandise of photosynthesis. The decreased molecules produced from the light dependent reactions are used in the light independent reactions to bring forth one of the concluding merchandises of photosynthesis. glucose.

Photosynthesis occurs in the foliage of workss in their chlorophyll. The pigment chlorophyll absorbs ruddy and bluish visible radiation and transmits green visible radiation. it is responsible for the green colour in workss ( Freeman 2002 ) . There are besides other pigments in workss such as provitamin As and luteins that help photosynthesis by increasing the scope of wavelengths or sum of light absorbed. This is good for the works because the more soaking up of photons. the more negatrons can be excited. and therefore photosynthesis can happen at a faster rate. Green visible radiation is reflected by works foliage and non absorbed and so it is my hypothesis that the Spinacia oleracea discs having green visible radiation will hold no photosynthetic reactions take topographic point. therefore no Spinacia oleracea disks lifting to the top. This is because the chlorophyll can non utilize the green visible radiation to excite negatrons because there is no measure difference–no difference in possible energy states–that correspond to the sum of energy in a green photon ( Freeman 2002 ) .

It is besides my hypothesis that the blue and ruddy visible radiation will excite photosynthesis because chlorophyll absorbs those colourss and utilizations those photons to trip photosynthetic reactions by electron excitement. Because the pigments of chlorophyll. chlorophyll a and chlorophyll b. absorb more bluish visible radiation than ruddy visible radiation. it is besides my hypothesis that the rate of photosynthesis will be higher with the blue visible radiation than the ruddy visible radiation. As for the xanthous visible radiation. because chlorophyll doesn’t absorb much xanthous visible radiation. my hypothesis is that with the yellow filter merely a little sum of Spinacia oleracea discs will drift to the top due to photosynthesis. The white visible radiation should hold the most photosynthesis because all of the colourss of the spectrum are available for the works to run photosynthesis. non merely one colour. In the presence of white visible radiation. the chlorophyll will be having both blue and ruddy which will increase the rate of photosynthesis.

My hypothesis for the rates of photosynthesis due to variable colour visible radiation in increasing order is: green. yellow. ruddy. blue and white.

In the undermentioned experiment. we will mensurate the photosynthetic rates of Spinacia oleracea discs under different wavelengths ( bluish. yellow. green. ruddy and white ) of visible radiation.

Materials and Methods

To mensurate the comparative rates of photosynthesis. we measured the production of a merchandise of the light dependent reactions. O. In order to make this. we used Spinacia oleracea foliage discs that we cut from Spinacia oleracea foliages. which were all the same size. We took about 50-60 Spinacia oleracea foliage discs and placed them in a flask incorporating 100 milliliter of 0. 2 % bicarbonate solution. NaHCO3. Using a H2O aspirator. we replaced the gas in the foliage discs with the 0. 2 % bicarbonate solution. This caused the Spinacia oleracea foliage discs to drop to the underside of the solution because the 0. 2 % bicarbonate solution is denser than the air spaces it replaced in the Spinacia oleracea foliage discs.

With five Petri dishes filled 2/3 to the top with 0. 2 % bicarbonate solution we placed 10 Spinacia oleracea discs that sunk to the underside in each of them. We used 0. 2 % bicarbonate solution once more in the Petri dishes because the discs remained sunk on the underside.

After. we set up our variable light intervention. Using 3 inundation lamps clamped to a metal base. we placed them about a pes above the tabular array. We so turned all of them on illuminated towards the tabular array. Because in our experiment we are merely proving the variable of light quality. we needed to maintain other variables controlled. The light strength needed to be kept controlled because if one Petri dish received a higher strength of visible radiation than the other. the consequences of the rate of photosynthesis may be due to the strength instead than the quality of the visible radiation. We used a lux metre and found five musca volitanss under the inundation lamps in which the visible radiation strength was 2000 lx with their several filters.

The variable interventions we used were exposing the deep-set Spinacia oleracea discs to different colourss of visible radiation. Using filters. our variable interventions were green visible radiation. ruddy visible radiation. bluish visible radiation and xanthous visible radiation. Our control intervention was utilizing white visible radiation. which didn’t have a filter. The control of merely white visible radiation is used to compare the rate of photosynthesis that occurs of course in the environment when all colourss of visible radiation are available to the chlorophyll. At the musca volitanss where the light strength was 2000 lx with their several filters. we placed a Petri dish under the colour filter and under a clear bowl incorporating H2O. The bowl incorporating H2O was used as a heat filter. absorbing the heat from the bulbs. because we didn’t want the heat impacting the Spinacia oleracea foliage discs and the rate of photosynthesis.

With this setup we measured the comparative rates of photosynthesis among the variable interventions. As the Spinacia oleracea discs under went photosynthesis. now that visible radiation was available. O was produced. The O replaced the 0. 2 % bicarbonate solution in the infinites of the Spinacia oleracea discs. doing the Spinacia oleracea discs to go less dense. If adequate O was produced. the Spinacia oleracea discs rose to the top of the Petri dish because the Spinacia oleracea discs became less dense than the 0. 2 % bicarbonate solution. We measured the rate of photosynthesis by mensurating the figure of discs out the 10 deep-set discs that rose to the top in a given sum of clip. If more discs rose to the top. more O was produced in the discs. meaning a higher photosynthetic rate.

Although it may look that we merely indirectly measured photosynthesis because O is a merchandise from photosystem II. non of photosystem I. So technically. the rate of photosystem I could hold been increasing. but we wouldn’t have detected it with our setup because O isn’t produced in photosystem I. However. because the photosystems overlap a batch in the soaking up and their rates. mensurating O was still a good step of the rate of photosynthesis that took topographic point.

We measured the sum of discs that floated to the top in each intervention every five min for 30 min. Originally. the clip intervals for reading were 10 min. but to obtain twice every bit many points and produce a better graph. we took readings every five min.


Figure 1.

Figure 1. % Spinacia oleracea discs drifting vs. clip due to variable light colour. In the experiment. as clip increased the per centum of Spinacia oleracea discs that floated increased in all of the colourss of light except green visible radiation which remained at nothing. Within the first five min. 40 per centum or more of the Spinacia oleracea discs had already risen to the top in four of the five interventions. The intervention in which that didn’t occur was in green visible radiation. which didn’t have any Spinacia oleracea discs rise throughout the 30 min. At 15 min. 100 % of Spinacia oleracea discs rose in white and ruddy visible radiation interventions and 90 % of blue’s discs and 80 % of yellow’s discs rose. After the 30 min. 100 % of the Spinacia oleracea discs rose to the top in all interventions except under the green visible radiation. Under the intervention of white visible radiation. 100 % of Spinacia oleracea discs rose to the top first followed by ruddy. blue and xanthous visible radiations. This is besides the order of the rates of photosynthesis under the different visible radiation interventions from highest to lowest rates.


Some of the consequences that we obtained are in understanding with my hypothesis. Mentioning to calculate 1. the light intervention to hold all the Spinacia oleracea discs rise to the top was in the white visible radiation. followed by ruddy visible radiation. bluish visible radiation. xanthous visible radiation and green visible radiation in which no Spinacia oleracea discs rose over the 30 min. Because all of the white light’s Spinacia oleracea discs rose in a less sum of clip than the other interventions. its photosynthetic rate must hold been faster. Therefore the rates of photosynthesis due to variable colour visible radiation in increasing order are: green. yellow. blue. ruddy and white. These consequences didn’t precisely back up my hypothesis. In my hypothesis. I thought bluish visible radiation would hold a higher rate of photosynthesis than the ruddy visible radiation. The consequences of xanthous visible radiation bring forthing a important rate of photosynthesis rejected my hypothesis. However. my hypothesis of green visible radiation bring forthing no photosynthesis and white visible radiation bring forthing the most did back up my hypothesis.

One account for these consequences that didn’t back up my hypothesis is imputing it to experimental mistake. Possibly when we measured the figure of discs that did float. we over counted as it was hard to find the deepness of each disc given merely a few centimetre of difference from drifting to staying on the underside. Another mistake that could hold occurred by experimentation is that the light strength at each Petri dish wasn’t precisely 2000 lx. It was easy to error to hold a higher light strength at one country than the other because merely little arrangement motions in the lx metre caused big alterations in the strength of visible radiation from the bulbs. Although we found points that were 2000 lx. when we removed our markers and placed the Petri dishes. we were a small off.

This could easy hold caused the mistake of ruddy visible radiation bring forthing a higher photosynthetic rate than bluish visible radiation. non because of the different moving ridge lengths but because the Petri dish receiving ruddy visible radiation by chance had a higher strength of visible radiation. Another measure where experimental mistake may hold occurred was when we aspirated the Spinacia oleracea discs. We may hold done it improperly and damaged the Spinacia oleracea discs so the rate of photosynthesis was thrown off from the damaged discs. Another experimental mistake that could hold occurred is that possibly our consequences are from a little sample size and that there were irregular Spinacia oleracea discs. So a follow up of retroflexing this experiment but utilizing twice every bit many Spinacia oleracea discs could take out opportunity mistake. the mistake due to an unusual sample size non representative of the full Spinacia oleracea disc population.

However. our consequences could be true and that my hypothesis needs to be reevaluated. There could be other pigments in the Spinacia oleracea leaf other than chlorophyll. Other pigments could increase the sum of soaking up due to certain wavelengths and besides increase the scope of wavelengths absorbed. Assuming no experimental mistake occurred and merely the chlorophyll pigment was present. the information of the photosynthetic rate from xanthous visible radiation shouldn’t be important. because the chlorophyll pigments don’t absorb much xanthous visible radiation. However. there could be other pigments that do absorb yellow visible radiation that we don’t know about in the Spinacia oleracea foliage that is absorbing the xanthous visible radiation photons. exciting negatrons and increasing the rate of photosynthesis. Likewise. this account of other pigments could besides explicate that ruddy visible radiation produced a higher photosynthetic rate than bluish visible radiation. Possibly there are other pigments that increase the sum of ruddy visible radiation absorbed and therefore ruddy visible radiation bring forthing a higher rate of photosynthesis than bluish visible radiation.

The following measure to find what pigments are in Spinacia oleracea foliage would be to make a paper chromatography of the Spinacia oleracea leaves. By making this we could divide the pigments of the Spinacia oleracea leaves and utilizing a spectrophotometer to mensurate the light wavelengths is absorbs. we could clearly find what wavelengths the Spinacia oleracea foliage absorbs. This manner we could find if merely chlorophyll pigments are present. and therefore can impute our informations to experimental mistake. or if there are other pigments moving in the system. which caused unexpected rates of photosynthesis in ruddy and xanthous visible radiation. which rejected my hypothesis of those two light colourss.

Another probe to see would be interesting to retroflex this experiment over once more. nevertheless taking readings in shorter intervals. for illustration every two min. This would bring forth a better graph than what we obtained because in our experiment taking readings every five min for 20 min about all the discs had all risen to the top by 15 min in all but the green intervention. For illustration. within the first five min. 80 per centum of the Spinacia oleracea discs under the white visible radiation had already risen. It would be interesting to see the photosynthetic rate when the discs are actively drifting to the top which occurred chiefly in the first 10 min. By taking more readings we could develop a better graph.

Literature Cited

Freeman. S. 2002. Biological Science. New Jersey: Prentice Hall.


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