The effect of light intensity on the amount of chlorophyll in "Cicer arietinum "

Extended Essay

Biology (SL)

"The effect of light intensity on the amount of chlorophyll in" Cicer arietinum "

Word count: 4 413 words

Content

Abstract ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 2
Introduction ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. 3
Hypothesis ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... 3
Method:
Description .. ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. 8
Results ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. 10
Discussion ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... .. 14
Conclusion ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... .. 14
Evaluation of the method ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .. ... ... 15
Bibliography ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... ... .... 16

Abstract.

Plants, growing on the shaded area has less concentrated green colorand are much longer and thinner than plants growing on the sun areas asthey are dark green, short and thick. Research question was: "How does theamount of chlorophyll-a and chlorophyll-b, gram per gram of plant, dependson the light intensity in which plants are placed? "

Hypothesis suggests that there are several inner and outer factorsthat affect the amount of chlorophylls a and b in plants and that with theincrease of light intensity the amount of chlorophyll will also increaseuntil light intensity exceeds the value when the amount of destructedchlorophylls is greater than formatted thus decreasing the total amount ofchlorophylls in a plant.

The seeds of Cicer arietinum were divided into seven groups andplaced into various places with different values of light intensities.
Light intensities were measured with digital colorimeter. After three weekslength was measured. Then plants were cut and quickly dried. Their biomasswas also measured. Three plants from each group were grinded and theethanol extract of pigments was prepared. The amount of chlorophylls wasmeasured using method of titration and different formulas.

The investigation showed that plants growing on the lowest lightintensity equal 0 lux contained no chlorophyll and had the longest length.
The amount of chlorophyll quickly increased and length decreased with theincrease of light intensity from 0 lux to 1200 lux. The amount ofchlorophyll in plants unpredictably decreased during light intensity equalto 142 lux and than continued increasing and didn't start decreasingreaching very high value (1200 lux).

The sudden decrease happened due to mighty existence of some innergenetical damages of seeds which prevented them from normal chlorophyllsynthesis and predicted decrease didn't decrease because extremely highlight intensity was not exceeded.

Word count: 300 words

I. Introduction.

This theme seemed to be attractive for me because I could see thatresults of my investigation could find application in real life.

While walking in the forest in summer I saw lots of plants ofdifferent shades of green color: some of them were dark green, some werelight green and some even very-very light green with yellow shades, hence Ibecame very interested in this situation and wanted to know why it happensto be so. I also saw that those plants that were growing on sunny parts offorest, where trees were not very high, had dark green color and those,that were growing in shady parts of the same forest had very light greencolor. They also had difference in their length and thickness - those, thatwere growing on light were very short, but thick and strong, and those,growing in shady regions were very thin and fragile.

Hence I became very interested in finding scientifical description of my observations.

The aim of my project is to find out how does the changes in lightintensity affect balance of chlorophyll in Cicer arietinum.

II. Hypothesis.

There are several factors that affect the development of chlorophyllin plants. [1]

Inner factors. The most important one is - genetical potential of aplant, because sometimes happen mutations that follow in inability ofchlorophyll formation. But most of the times it happens that the process ofchlorophyll synthesis is broken only partly, revealing in absence ofchlorophyll only in several parts of the plant or in general low rate ofchlorophyll. Therefore plants obtain yellowish color. Lots of genesparticipate in the process of chlorophyll synthesis, therefore differentanomalies are widely represented. Development of chloroplasts depends onnuclear and plastid DNA and also on cytoplasmatic and chloroplasticribosomes.

Full provision of carbohydrates seem to be essential for chlorophyllformation, and those plants that suffer from deficit of solublecarbohydrates may not become green even if all other conditions areperfect. Such leaves, placed into sugar solution normally start to formchlorophyll. Very often it happens that different viruses preventchlorophyll formation, causing yellow color of leaves.

Outside factors. The most important outside factors, affecting theformation of chlorophyll are: light intensity, temperature, pH of soil,provision of minerals, water and oxygen. Synthesis of chlorophyll is verysensitive to all the factors, disturbing metabolic processes in plants.

Light. Light is very important for the chlorophyll formation, though someplants are able to produce chlorophyll in absolute darkness. Relatively lowlight intensity is rather effective for initialization and speeding ofchlorophyll development. Green plants grown in darkness have yellow colorand contain protochlorophyll - predecessor of chlorophyll а, which needslite to restore until chlorophyll а. Very high light intensity causes thedestruction of chlorophyll. Hence chlorophyll is synthesized and destructedboth at the same time. In the condition of very high light intensitybalance is set during lower chlorophyll concentration, than in condition oflow light intensity.

Temperature. Chlorophyll synthesis seems to happen during rather broadtemperature intervals. Lots of plants of помірної зони synthesizechlorophyll from very low temperatures till very high temperatures in themid of the summer. Many pine trees loose some chlorophyll during wintersand therefore loose some of their green color. It may happen because thedestruction of chlorophyll exceeds its formation during very lowtemperatures.

Provision with minerals. One of the most common reason for shortage ofchlorophyll is absence of some important chemical elements. Shortage ofnitrogen is the most common reason for lack of chlorophyll in old leaves.
Another one is shortage of ferrum, mostly in young leaves and plants. Andferrum is important element for chlorophyll synthesis. And magnesium is acomponent of chlorophyll therefore its shortage causes lack of productionof chlorophyll.

Water. Relatively low water stress lowers speed of chlorophyll synthesisand high dehydration of plants tissues not only disturbs synthesis ofchlorophyll, but even causes destruction of already existing molecules.

Oxygen. With the absence of oxygen plants do not producechlorophyll even on high light intensity. This shows that aerobicrespiration is essential for chlorophyll synthesis.

Chlorophyll. [2] The synthesis of chlorophyll is induced by light.
With light, a gene can be transcripted and translated in a protein.
The plants are naturally blocked in the conversion of protochlorophyllideto chlorophyllide. In normal plants these results in accumulation of asmall amount of protochlorophyllide which is attached to holochromeprotein. In vivo at least two types of protochlorophyllide holochrome arepresent. One, absorbing maximally at approximately 650 nm, is immediatelyconvertible to chlorophyllide on exposure to light. If ALA is given toplant tissue in the dark, it feeds through all the way toprotochlorophyllide, but no further. This is because POR, the enzyme thatconverts protochlorophyllide to chlorophyllide, needs light to carry outits reaction. POR is a very actively researched enzyme worldwide and a lotis known about the chemistry and molecular biology of its operation andregulation. Much less is known about how POR works in natural leafdevelopment.

ALA Portoporphyrine

Protochlorophyllide

Chlophyllide

Chlorophyll b Chlorophyll a

Chlorophyll [3] is a green compound found in leaves and green stems ofplants. Initially, it was assumed that chlorophyll was a single compoundbut in 1864 Stokes showed by spectroscopy that chlorophyll was a mixture.
If dried leaves are powdered and digested with ethanol, after concentrationof the solvent, 'crystalline' chlorophyll is obtained, but if ether oraqueous acetone is used instead of ethanol, the product is 'amorphous'chlorophyll.

In 1912, Willstatter et al. (1) showed that chlorophyll was a mixtureof two compounds, chlorophyll-a and chlorophyll-b:

Chlorophyll-a (C55H72MgN4O5, mol. wt.: 893.49). The methyl group markedwith an asterisk is replaced by an aldehyde in chlorophyll-b (C55H70MgN4O6,mol. wt.: 906.51).

The two components were separated by shaking a light petroleumsolution of chlorophyll with aqueous methanol: chlorophyll-a remains in thelight petroleum but chlorophyll-b is transferred into the aqueous methanol.
Cholorophyll-a is a bluish-black solid and cholorophyll-b is a dark greensolid, both giving a green solution in organic solutions. In naturalchlorophyll there is a ratio of 3 to 1 (of a to b) of the two components.

The intense green colour of chlorophyll is due to its strongabsorbencies in the red and blue regions of the spectrum, shown in fig. 1.
(2) Because of these absorbencies the light it reflects and transmitsappears green.

Fig. 1 - The uv/visible adsorption spectrum for chlorophyll.

Due to the green colour of chlorophyll, it has many uses as dyes andpigments. It is used in colouring soaps, oils, waxes and confectionary.

Chlorophyll's most important use, however, is in nature, inphotosynthesis. It is capable of channelling the energy of sunlight intochemical energy through the process of photosynthesis. In this process theenergy absorbed by chlorophyll transforms carbon dioxide and water intocarbohydrates and oxygen:

CO2 + H2O (CH2O) + O2

Note: CH2O is the empirical formula of carbohydrates.

The chemical energy stored by photosynthesis in carbohydrates drivesbiochemical reactions in nearly all living organisms.

In the photosynthetic reaction electrons are transferred from water tocarbon dioxide, that is carbon dioxide is reduced by water. Chlorophyllassists this transfer as when chlorophyll absorbs light energy, an electronin chlorophyll is excited from a lower energy state to a higher energystate. In this higher energy state, this electron is more readilytransferred to another molecule. This starts a chain of electron-transfersteps, which ends with an electron being transferred to carbon dioxide.
Meanwhile, the chlorophyll which gave up an electron can accept an electronfrom another molecule. This is the end of a process which starts with theremoval of an electron from water. Thus, chlorophyll is at the centre ofthe photosynthetic oxidation-reduction reaction between carbon dioxide andwater.

Treatment of cholorophyll-a with acid removes the magnesium ionreplacing it with two hydrogen atoms giving an olive-brown solid,phaeophytin-a. Hydrolysis of this (reverse of esterification) splits offphytol and gives phaeophorbide-a. Similar compounds are obtained ifchlorophyll-b is used.

Chlorophyll can also be reacted with a base which yields a series ofphyllins, magnesium porphyrin compounds. Treatment of phyllins with acidgives porphyrins.

Now knowing all these factors affecting the synthesis and destructionof chlorophyll I propose that the amount of chlorophyll in plant depends onlight intensity in the following way: with the increase of light intensitythe amount of chlorophyll increases, but then it starts decreasing becauselight intensity exceed the point when there is more chlorophyll destructedthan formed.

Variables.

Independent:

. Light intensity, lux
Constant:

. pH of soil

. water supply, ml

. temperature, to C
Dependent:

. length, cm

. amount of chlorophyll in gram of a plant, gram per gram

III. Method.

Apparatus:

. seeds of Cicer arietinum

. 28 plastic pots

. water

. scissors

. ruler (20 cm (0.05 cm)

. CaCO3

. soil (adopted for home plants)

. digital luxmeter ((0.05 lux)

. test tubes

. H2SO4 (0.01 M solution)

. Pipette (5 cm3 (0.05 cm3)

. mortar and pestle

. burette

. ethanol (C2H5OH), 98%

. beakers

Firstly I went to the shop and bought germinated seeds of Cicerarietinum. Then sorted seeds and chose the strongest ones. After that Iprepared soil for them and put them in it.

As the aim of this project is to investigate the dependence of mass ofchlorophyll in plants during different light intensities it was needed tocreate those various conditions. Pots with seeds were placed into thefollowing places: in the wardrobe with doors (light intensity is o lux),under the sink (light intensity is 20,5 lux), in the shell of bookcase
(light intensity is 27,5 lux), above the bookcase (light intensity is 89,5lux), above the extractor (light intensity is 142 lux), beyond the curtains
(light intensity is 680 lux) and on the open sun (light intensity is 1220lux). Light intensity was measured with the help of digital luxmeter. Itwas measured four times each day: morning, midday, afternoon, evening.
During those four periods four measurements were done and the maximum valuewas taken into consideration and written down. Those measurements lastedfor three weeks of the experiment as the whole time of the experiment wasthree weeks. The luxmeter's sensitive part was placed on the plants (so itwas just lying on them) in order to measure light intensity flowingdirectly on plant bodies, then two minutes were left in order to getstabilized value of light intensity and the same procedure was repeated.
All those actions were done in order to get more accurate results of lightintensity.

Growing plants were provided with the same amount of water (15 ml, once aday in the morning) and they were situated in the same room temperature
(20o C), pH of soil was definitely the same because all the plants were putin the same soil (special soil for room flowers).

After three weeks past the length of plants was measured with the help ofruler. Firstly the plants were not cut, so their length had to be measuredwhile they were in the pots. The ruler was placed into the pot and plantswere carefully stretched on it. The action was repeated three times andonly maximum value was taken into consideration. After that plants werecut. Then those already cut plants were put into the dark place and quicklydried.

Titration.

I have chosen three plants from each light intensity group and measuredtheir weight. . In order to obtain the pigments, three plants were cut intosmall pieces and placed in a mortar. Calcium carbonate was then added,together with a little ethanol (2 cm3). The leaf was grinded using a pestleuntil no large pieces of leaf tissue were left, and the remaining ethanolwas poured into the mortar (3 cm3). Then 1 ml of obtained solution wasplaced into the test tube and this 1 ml of solution was then titratedagainst 0.01 M solution of sulfuric acid, through the use of a pipette. Thetitration was complete when the green solution turned dark olive-green [4].
This solution obtained from the first action was stored as the etalon forthe following ones. The settled olive-green coloring meant that allchlorophyll had reacted with H2SO4. So the process of titration wasrepeated 7 times for all light intensity groups.

The solution is titrated until the dark olive-green color because it isknown that when the reaction between chlorophyll and sulfuric acid happens,chlorophyll turns into phaeophetin which has grey color (see table 1),therefore when the solution is olive-green, than the reaction hassucceeded. But while searching in the internet and books I found out thatthere are several opinions about the color of phaeophytin - in the bookwritten by Viktorov it is ssaid to have grey color, but in the internetlink http://www.ch.ic.ac.uk/local/projects/steer/chloro.htm it is said tohave brown olive-green color. Also I made chromatography in order toinvestigate the color of phaeophytin and the result was that it has greycolor. It can be proposed that olive-green color is obtained because greyphaeophetyn is mixed with other plant pigments.

So titration is one of the visual methods that can be used in order tofind the mass of chlorophyll in plants.

All the measurements and even chromatography were done three times andthe mean value was taken, for chromatography grey color was confirmed.

Table 1. Plant pigments.

IV. Results.

Table 2. Raw data.

| Number of | Light intensity (lux) |
| plant | |
| 0 | 0,273 | 0,041 | 84,98 | 41,89 | 0,0000 |
| 20,5 | 0,579 | 0,056 | 90,33 | 41,76 | 0,0496 |
| 27,5 | 0,332 | 0,033 | 90,06 | 36,33 | 0,1462 |
| 89,5 | 0,181 | 0,018 | 90,06 | 19,81 | 0,1769 |
| 142 | 0,511 | 0,047 | 90,80 | 41,33 | 0,0697 |
| 680 | 0,338 | 0,043 | 87,28 | 29,33 | 0,1557 |
| 1220 | 0,301 | 0,034 | 88,70 | 18,64 | 0,1939 |

Calculation of amount of chlorophyll in plants basing on the results oftitration

H2 SO4 + C56 O5 N4 Mg => C56 O5 N4 H + MgSO4
Concentration of H2SO4 is 0,01 M
C - concentration
V - volumen - quantity of substancym - mass
Mr - molar mass

For light intensity equal to 20,5 lux.n = V (in dm3)? C
2? 10-3? 0,01 = 2? 10-5n = m/Mr => m = n? Mrm = 2? 10-5? 832 = 1,664? 10-2 gramsmass of plant mass of chlorophyll
1,68 grams - 0,08335 grams ofchlorophyll
1 gram - x grams ofchlorophyll
Hence there are 0,0496 grams of chlorophyll.

Table 5. The correlation between mean length of plants and mean drybiomass.

| | | | | | | |

Table 6. The correlation between mean length and mass of chlorophyll per 1g of plant.

R2) | D ^ 2 | | 1 | 41,89 | 1 | 0,0000 | 7 | -6 | 36 | | 2 | 41,76 | 2 | 0,0496 | 6 | -4

| 16 | | 3 | 36,33 | 4 | 0,1462 | 4 | 0 | 0 | | 4 | 19,81 | 6 | 0,1769 | 2 | 4 | 16 | | 5
| 41,33 | 3 | 0,0697 | 5 | -2 | 4 | | 6 | 29,33 | 5 | 0,1557 | 3 | 2 | 4 | | 7 | 18,64 | 7
| 0,1939 | 1 | 6 | 36 | | | | | | | | | |
Rs = -1

| | | | | | | | | | | | | | | |

Table 7. The correlation between mean dry biomass and mass of chlorophyllper 1 g of plant.

Site | Mean dry biomass, g | Rank (R1) | Mass of chl. In 1 g | Rank (R2) | D
(R1-R2) | D ^ 2 | | 1 | 0,041 | 4 | 0,0000 | 7 | -3 | 9 | | 2 | 0,056 | 1 | 0, 0496 | 6 | -5

| 25 | | 3 | 0,033 | 6 | 0,1462 | 4 | 2 | 4 | | 4 | 0,018 | 7 | 0,1769 | 2 | 5 | 25 | | 5
| 0,047 | 2 | 0,0697 | 5 | -3 | 9 | | 6 | 0,043 | 3 | 0,1557 | 3 | 0 | 0 | | 7 | 0,034 | 5
| 0,1939 | 1 | 4 | 16 | | | | | | | | | | | | | | | | | | Rs = -0,57 | | | | | |
| |

| | | | | | | | | | | | | | | | | | | | | | | |

V. Discussion.

Several tendencies can be clearly seen.

For the first, with the increase of light intensity mean length ofplants is decreasing, but there are exceptions. For light intensity 142 luxthe value of mean length is approximately equal to the values of length forlight intensities 0 lux and 20,5 lux. If exclude this data it is also seenthat for light intensity equal to 680 lux mean length is also slightlyfalling out from the main tendency - decreasing from 19.81 cm.

The second tendency is increase of mass of chlorophyll per 1 gram ofplant biomass with the increase of light intensity. But the values of massof chlorophyll of those plants under light intensities 142 lux and 680 luxare falling out from the main tendency. The first and the second ones aretoo small - approximately equal to the value corresponding to 20.5 luxlight intensity and to 89.5 lux respectively. This may happen because notall the seeds of Cicer arietnum were of the same quality, because it isimpossible to guarantee that more than 250 seeds in one box have the samehigh quality. At the mean time it was expected that starting from the lightintensity more than 680 lux the amount of chlorophyll in plants willdecrease, because the value of destructed chlorophyll with be bigger thanthe value of newly formatted. But the experiments showed that the amount ofchlorophyll was constantly increasing even when the light intensity levelexceeded the point 1220 lux. This could happen because light intensityequal to 1220 lux is not so extremely high that the amount of totalchlorophyll in plants will start decreasing.

Also it is clearly seen that there are no correlations between lightintensity and values of wet and dry biomass.

Basing on these arguments the sudden decrease of the amount ofchlorophyll in plants placed on light intensity equal to 142 lux was likelyto be insignificant and could not be considered as a trend.

But it is impossible to forget such important factor as plant hormonesthat affect the growth and development of plants. There are five generallyaccepted types of hormones that influence plant growth and development.
They are: auxin, cytokinin, gibberellins, abscic acid, and ethylene. It isnot one hormone that directly influences by sheer quantity. The balance andratios of hormones present is what helps to influence plant reactions. Thehormonal balance possibly regulates enzymatic reactions in the plant byamplifying them.

VI. Conclusion.

Due to results of my investigation it is seen that my hypothesisdidn't confirm fully (for example, comparing the diagram 1 and diagram 7),because I proposed that when light intensities will be very high, mass ofchlorophyll in plant will start decreasing and due to my observations itdidn't happen. I should say that the only reason I can suggest is that Ihaven't investigated such extremely high light intensities, so thatchlorophyll start destructing. But if we will not pay attention to thatfact the other part of my hypothesis was confirmed and mass of chlorophyllin plants increased with the increase of light intensity. Furthermore Ididn't estimate amount of plant hormones and so didn't estimate theirinfluence on results.

Questions for further investigation:

1. Investigating very high light intensities.

2. Implementation of colorimetric analysis.

3. Paying attention to estimation of plant hormones level.

Those questions should be further investigated in order to get clearerpicture and more accurate results of the dependence of the amount ofchlorophyll in plants on the light intensity, knowing the fact that theamount of chlorophyll has a tendency to decrease at extremely high lightintensities. So this statement needs an experimental confirmation and as inthis investigation conditions with extremely light intensity were notcreated in further investigations they have to be created.

Implementation of colorimetric analysis is also very important thing,because it gives much more accurate results comparing with the titrationmethod. The colorimetric method suggests that as different pigments absorbdifferent parts of light spectrum differently, the absorbance of a pigmentsmixture is a sum of individual absorption spectra. Therefore the quantityof each individual pigment in a mixture can be calculated using absorbanceof the certain colors and molecular coefficients of each pigment. This wasproposed by D. A. Sims, and J. A. Gamon (California State University,
USA) [5] with the reference on Lichtenthaler (1987).

VII. Evaluation.

There are several results in my work, that are falling out from themain tendencies. It may seem that such results may occur due to differentpercentage of water in plants, but when I was calculating mass ofchlorophyll in 1 gram of plant I was using only values of mean dry biomassso it couldn't affect my results. (see table 3)

At the same time such differences in the percentage of water areeasily explained. The rate of evaporation of water from plants, which wereput 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 mayvary, though I provided all the plants with the same volume of water at thesame periods of time.

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

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

Even those who do not suffer from this disease can also make mistakesin such experiment. It is known that people who suffer from Myopia canhardly see objects that are far from them, but don't have problems withobjects that are near, but it is also important to take into considerationthe fact that their ability to distinguish colors is also lower comparingwith humans with normal eyesight.

There also exist the so called human factor, which also affects theinvestigation. Man can't be absolutely objective, because sometimes it istoo hard for a person to falsify his own theory or hypothesis, so one canignore results that are not suitable for his statements and select onlythose that are suitable, which will also affect the investigation not ingood way.

So as human's eye is not a perfect instrument and humans are notperfectly objective there should be other methods of investigating theamount of chlorophyll in plant.

Moreover titration method doesn't distinguish between chlorophylls-aand chlorophyll-b, phaeophytin-a and phaeophytin-b, as their colors differ,this giving not very accurate results. Also due to this limiting factor itis impossible to know whether the whole amount of chlorophyll reacted withthe sulfuric acid and again it adds an uncertainty to the results.
Furthermore the saturation of color depends on the extent of dilution andit is nearly impossible to say if the solution was diluted till the samecolor or not, because it is very difficult to distinguish between differentshades 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) Вікторів Д. П., Практикум з фізіології рослин. - 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

-----------------------< br>[1] http://www.bonsai.ru/dendro/physiology5.html 02/04/2004

[2] www.iger.bbsrc.ac.uk/igdev/iger_innovations/ 06/05/2004
[3] http://www.ch.ic.ac.uk/local/projects/steer/chloro.htm 11/04/2004
[4] 8: B> @> 2. ., @ 0: B8: C D878>;> 388 Вікторів Д. П., Практикум пофізіології рослин. - 2-е изд. - Воронеж: ВГУ, 1991, p.66
[5] http://vcsars.calstatela.edu/esa_posters/ds/dan_esa99.html 05/05/2004

------------------ -----< br>Chlorophyll, gram per gram of plant.

Light intensity, lux

Diagram 1. The predicted change of amount of chlorophyll in leaves ofdepending on light intensity

0,57