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The effect of light intensity on the amount of chlorophyll in “Cicer arietinum” |
Ex e ded Essay Biology (SL) “ he effec of ligh i e si y o he amou of chlorophyll i “Cicer arie i um”Word cou : 4 413 words Co e Abs rac 2 I roduc io . 3 Hypo hesis 3 Me hod: Descrip io . . 8 Resul s . 10 Discussio . . 14 Co clusio . . 14 Evalua io of he me hod . 15 Bibliography . 16 Abs rac . Pla s, growi g o he shaded area has less co ce ra ed gree color a d are much lo ger a d hi er ha pla s growi g o he su areas as hey are dark gree , shor a d hick. Research ques io was: “How does he amou of chlorophyll-a a d chlorophyll-b, gram per gram of pla , depe ds o he ligh i e si y i which pla s are placed?” Hypo hesis sugges s ha here are several i er a d ou er fac ors ha affec he amou of chlorophylls a a d b i pla s a d ha wi h he i crease of ligh i e si y he amou of chlorophyll will also i crease u il ligh i e si y exceeds he value whe he amou of des ruc ed chlorophylls is grea er ha forma ed hus decreasi g he o al amou of chlorophylls i a pla . he seeds of Cicer arie i um were divided i o seve groups a d placed i o various places wi h differe values of ligh i e si ies. Ligh i e si ies were measured wi h digi al colorime er. Af er hree weeks le g h was measured. he pla s were cu a d quickly dried. heir biomass was also measured. hree pla s from each group were gri ded a d he e ha ol ex rac of pigme s was prepared. he amou of chlorophylls was measured usi g me hod of i ra io a d differe formulas. he i ves iga io showed ha pla s growi g o he lowes ligh i e si y equal 0 lux co ai ed o chlorophyll a d had he lo ges le g h. he amou of chlorophyll quickly i creased a d le g h decreased wi h he i crease of ligh i e si y from 0 lux o 1200 lux. he amou of chlorophyll i pla s u predic ably decreased duri g ligh i e si y equal o 142 lux a d ha co i ued i creasi g a d did ’ s ar decreasi g reachi g very high value (1200 lux). he sudde decrease happe ed due o migh y exis e ce of some i er ge e ical damages of seeds which preve ed hem from ormal chlorophyll sy hesis a d predic ed decrease did ’ decrease because ex remely high ligh i e si y was o exceeded. Word cou : 300 words I. I roduc io . his heme seemed o be a rac ive for me because I could see ha resul s of my i ves iga io could fi d applica io i real life. While walki g i he fores i summer I saw lo s of pla s of differe shades of gree color: some of hem were dark gree , some were ligh gree a d some eve very-very ligh gree wi h yellow shades, he ce I became very i eres ed i his si ua io a d wa ed o k ow why i happe s o be so. I also saw ha hose pla s ha were growi g o su y par s of fores , where rees were o very high, had dark gree color a d hose, ha were growi g i shady par s of he same fores had very ligh gree color. hey also had differe ce i heir le g h a d hick ess – hose, ha were growi g o ligh were very shor , bu hick a d s ro g, a d hose, growi g i shady regio s were very hi a d fragile. He ce I became very i eres ed i fi di g scie ifical descrip io of my observa io s. he aim of my projec is o fi d ou how does he cha ges i ligh i e si y affec bala ce of chlorophyll i Cicer arie i um.
II. Hypo hesis. here are several fac ors ha affec he developme of chlorophyll i pla s.1 I er fac ors. he mos impor a o e is – ge e ical po e ial of a pla , because some imes happe mu a io s ha follow i i abili y of chlorophyll forma io . Bu mos of he imes i happe s ha he process of chlorophyll sy hesis is broke o ly par ly, reveali g i abse ce of chlorophyll o ly i several par s of he pla or i ge eral low ra e of chlorophyll. herefore pla s ob ai yellowish color. Lo s of ge es par icipa e i he process of chlorophyll sy hesis, herefore differe a omalies are widely represe ed. Developme of chloroplas s depe ds o uclear a d plas id D A a d also o cy oplasma ic a d chloroplas ic ribosomes. Full provisio of carbohydra es seem o be esse ial for chlorophyll forma io , a d hose pla s ha suffer from defici of soluble carbohydra es may o become gree eve if all o her co di io s are perfec . Such leaves, placed i o sugar solu io ormally s ar o form chlorophyll. Very of e i happe s ha differe viruses preve chlorophyll forma io , causi g yellow color of leaves. Ou side fac ors. he mos impor a ou side fac ors, affec i g he forma io of chlorophyll are: ligh i e si y, empera ure, pH of soil, provisio of mi erals, wa er a d oxyge . Sy hesis of chlorophyll is very se si ive o all he fac ors, dis urbi g me abolic processes i pla s. Ligh . Ligh is very impor a for he chlorophyll forma io , hough some pla s are able o produce chlorophyll i absolu e dark ess. Rela ively low ligh i e si y is ra her effec ive for i i ializa io a d speedi g of chlorophyll developme . Gree pla s grow i dark ess have yellow color a d co ai pro ochlorophyll – predecessor of chlorophyll а, which eeds li e o res ore u il chlorophyll а. Very high ligh i e si y causes he des ruc io of chlorophyll. He ce chlorophyll is sy hesized a d des ruc ed bo h a he same ime. I he co di io of very high ligh i e si y bala ce is se duri g lower chlorophyll co ce ra io , ha i co di io of low ligh i e si y. empera ure. Chlorophyll sy hesis seems o happe duri g ra her broad empera ure i ervals. Lo s of pla s of умеренной зоны sy hesize chlorophyll from very low empera ures ill very high empera ures i he mid of he summer. Ma y pi e rees loose some chlorophyll duri g wi ers a d herefore loose some of heir gree color. I may happe because he des ruc io of chlorophyll exceeds i s forma io duri g very low empera ures. Provisio wi h mi erals. O e of he mos commo reaso for shor age of chlorophyll is abse ce of some impor a chemical eleme s. Shor age of i roge is he mos commo reaso for lack of chlorophyll i old leaves. A o her o e is shor age of ferrum, mos ly i you g leaves a d pla s. A d ferrum is impor a eleme for chlorophyll sy hesis. A d mag esium is a compo e of chlorophyll herefore i s shor age causes lack of produc io of chlorophyll. Wa er. Rela ively low wa er s ress lowers speed of chlorophyll sy hesis a d high dehydra io of pla s issues o o ly dis urbs sy hesis of chlorophyll, bu eve causes des ruc io of already exis i g molecules. Oxyge . Wi h he abse ce of oxyge pla s do o produce chlorophyll eve o high ligh i e si y.
his shows ha aerobic respira io is esse ial for chlorophyll sy hesis. Chlorophyll.2 he sy hesis of chlorophyll is i duced by ligh . Wi h ligh , a ge e ca be ra scrip ed a d ra sla ed i a pro ei . he pla s are a urally blocked i he co versio of pro ochlorophyllide o chlorophyllide. I ormal pla s hese resul s i accumula io of a small amou of pro ochlorophyllide which is a ached o holochrome pro ei . I vivo a leas wo ypes of pro ochlorophyllide holochrome are prese . O e, absorbi g maximally a approxima ely 650 m, is immedia ely co ver ible o chlorophyllide o exposure o ligh . If ALA is give o pla issue i he dark, i feeds hrough all he way o pro ochlorophyllide, bu o fur her. his is because POR, he e zyme ha co ver s pro ochlorophyllide o chlorophyllide, eeds ligh o carry ou i s reac io . POR is a very ac ively researched e zyme worldwide a d a lo is k ow abou he chemis ry a d molecular biology of i s opera io a d regula io . Much less is k ow abou how POR works i a ural leaf developme . ALA Por oporphyri e Pro ochlorophyllide POR Chlophyllide Chlorophyll b Chlorophyll a Chlorophyll3 is a gree compou d fou d i leaves a d gree s ems of pla s. I i ially, i was assumed ha chlorophyll was a si gle compou d bu i 1864 S okes showed by spec roscopy ha chlorophyll was a mix ure. If dried leaves are powdered a d diges ed wi h e ha ol, af er co ce ra io of he solve , 'crys alli e' chlorophyll is ob ai ed, bu if e her or aqueous ace o e is used i s ead of e ha ol, he produc is 'amorphous' chlorophyll. I 1912, Wills a er e al. (1) showed ha chlorophyll was a mix ure of wo compou ds, chlorophyll-a a d chlorophyll-b: Chlorophyll-a (C55H72Mg 4O5, mol. w .: 893.49). he me hyl group marked wi h a as erisk is replaced by a aldehyde i chlorophyll-b (C55H70Mg 4O6, mol. w .: 906.51). he wo compo e s were separa ed by shaki g a ligh pe roleum solu io of chlorophyll wi h aqueous me ha ol: chlorophyll-a remai s i he ligh pe roleum bu chlorophyll-b is ra sferred i o he aqueous me ha ol. Cholorophyll-a is a bluish-black solid a d cholorophyll-b is a dark gree solid, bo h givi g a gree solu io i orga ic solu io s. I a ural chlorophyll here is a ra io of 3 o 1 (of a o b) of he wo compo e s. he i e se gree colour of chlorophyll is due o i s s ro g absorbe cies i he red a d blue regio s of he spec rum, show i fig. 1. (2) Because of hese absorbe cies he ligh i reflec s a d ra smi s appears gree .Fig. 1 - he uv/visible adsorp io spec rum for chlorophyll. Due o he gree colour of chlorophyll, i has ma y uses as dyes a d pigme s. I is used i colouri g soaps, oils, waxes a d co fec io ary. Chlorophyll's mos impor a use, however, is i a ure, i pho osy hesis. I is capable of cha elli g he e ergy of su ligh i o chemical e ergy hrough he process of pho osy hesis. I his process he e ergy absorbed by chlorophyll ra sforms carbo dioxide a d wa er i o carbohydra es a d oxyge :CO2 H2O (CH2O) O2 o e: CH2O is he empirical formula of carbohydra es. he chemical e ergy s ored by pho osy hesis i carbohydra es drives biochemical reac io s i early all livi g orga isms. I he pho osy he ic reac io elec ro s are ra sferred from wa er o carbo dioxide, ha is carbo dioxide is reduced by wa er.
This large amount of methane would also have to hide under the clouds. Both greenhouse models have the virtue of invoking only gases thought to exist on Titan; of course, both gases might play a role. An alternative model of the Titan atmosphere was proposed by the late Robert Danielson and his colleagues at Princeton University. They suggest that small quantities of simple hydrocarbons-such as ethane, ethylene and acetylene-which have been observed in the upper atmosphere of Titan absorb ultraviolet light from the Sun and heat the upper atmosphere. It is then the hot upper atmosphere and not the surface that we see in the infrared. On this model there need be no enigmatically warm surface, no greenhouse effect, and no atmospheric pressure of hundreds of millibars. Which view is correct? At the present time no one knows. The situation is reminiscent of studies of Venus in the early 1960s when the planetБЂ™s radio-brightness temperature was known to be high, but whether the emission was from a hot surface or a hot region of the atmosphere was (appropriately) hotly debated
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