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VII. Evaluation.

There are several results in my work, that are falling out from the main tendencies. It may seem that such results may occur due to different percentage of water in plants, but when I was calculating mass of chlorophyll in 1 gram of plant I was using only values of mean dry biomass so it couldn’t affect my results. (see table 3)

At the same time such differences in the percentage of water are easily explained. The rate of evaporation of water from plants, which were put under 1220 lux light intensity was much higher than of those put under
20.5 lux light intensity, therefore percentage of water in the soil may vary, though I provided all the plants with the same volume of water at the same periods of time.

One more reason that could be proposed is the reason connected with the pH of water with which flowers were provided. It was not measured but the thing that could have happened is that it had somehow changed the pH of soil in which seeds were placed and therefore changed the amount of synthesized chlorophyll.

Titration is not a perfect way of obtaining results. This happens because the method is based on visual abilities of a person – he has to decide whether the color he obtained is dark olive-green or not so dark olive-green. Such a situation concerns lots of mistakes due to different optical abilities of each person, even some humans are not able to distinguish those colors, because of the disease called Daltonism.

Even those who do not suffer from this disease can also make mistakes in such experiment. It is known that people who suffer from Myopia can hardly see objects that are far from them, but don’t have problems with objects that are near, but it is also important to take into consideration the fact that their ability to distinguish colors is also lower comparing with humans with normal eyesight.

There also exist the so called human factor, which also affects the investigation. Man can’t be absolutely objective, because sometimes it is too hard for a person to falsify his own theory or hypothesis, so one can ignore results that are not suitable for his statements and select only those that are suitable, which will also affect the investigation not in good way.

So as human’s eye is not a perfect instrument and humans are not perfectly objective there should be other methods of investigating the amount of chlorophyll in plant.

Moreover titration method doesn’t distinguish between chlorophylls-a and chlorophyll-b, phaeophytin-a and phaeophytin-b, as their colors differ, this giving not very accurate results. Also due to this limiting factor it is impossible to know whether the whole amount of chlorophyll reacted with the sulfuric acid and again it adds an uncertainty to the results.
Furthermore the saturation of color depends on the extent of dilution and it is nearly impossible to say if the solution was diluted till the same color or not, because it is very difficult to distinguish between different shades of olive green color.

BIBLIOGRAPHY

1) Allott, Biology for IB diploma (standard and higher level), Oxford

University Press, ISBN 0-19914818

2) M. Roberts, M. Reisse, G. Monger, Biology: principles and approaches,

Nelson, ISBN 0-17-44-8176-4

3) T. King, M. Reiss, M. Roberts, Practical advanced biology, Nelson

Thorns, ISBN 0-170448308-

4) Викторов Д. П., Практикум по физиологии растений. – 2-е изд.

– Воронеж: ВГУ, 1991

5) http://www.ac-creteil.fr/svt/Tp/Tp2/Tp2UK2/fiches_them_choix-

P2/genechloro.doc, 15/03/2004

6) http://vcsars.calstatela.edu/esa_posters/ds/dan_esa99.html 05/05/2004

7) http://www.agsci.ubc.ca/courses/fnh/410/colour/3_21.htm, 16/03/2004

8) http://vcsars.calstatela.edu/esa_posters/ds/dan_esa99.html, 22/02/2004

9) http://www.charlies-web.com/specialtopics/anthocyanin.html. 17/04/2004
10) http://www.ch.ic.ac.uk/local/projects/steer/chloro.htm, 11/04/2004
11) http://www.bonsai.ru/dendro/physiology5.html 02/04/2004
12) http://www.iger.bbsrc.ac.uk/Publications/Innovations/in97/Ch2.pdf,

06/05/2004

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