Editing Chlorophyll (section)

==Measurement of chlorophyll content==
[[File:Chlorophyll Extraktion.jpg|thumb|Chlorophyll forms deep green solutions in organic solvents.]]
Chlorophylls can be extracted from the protein into organic solvents.<ref name=Marker1972>{{Cite journal | vauthors = Marker AF | year = 1972 | title = The use of acetone and methanol in the estimation of chlorophyll in the presence of phaeophytin in plant | journal = Freshwater Biology | volume = 2 | pages = 361–385 | doi = 10.1111/j.1365-2427.1972.tb00377.x | issue = 4 }}</ref><ref name=Jeffrey1969>{{Cite journal | vauthors = Jeffrey SW, Shibata | date = February 1969 | title = Some Spectral Characteristics of Chlorophyll c from Tridacna crocea Zooxanthellae | journal = [[Biological Bulletin]] | volume = 136 | issue = 1 | pages = 54–62 | doi = 10.2307/1539668 | jstor = 1539668 | url = https://www.biodiversitylibrary.org/part/25503 }}</ref><ref>{{cite web | vauthors = Gilpin L |date=21 March 2001 |title=Methods for analysis of benthic photosynthetic pigment |publisher=School of Life Sciences, [[Napier University]] |url=http://www.lifesciences.napier.ac.uk/teaching/MB/benchl01.html |access-date=2010-07-17 |url-status=dead |archive-url=https://web.archive.org/web/20080414215124/http://www.lifesciences.napier.ac.uk/teaching/MB/benchl01.html |archive-date=April 14, 2008 }}</ref> In this way, the concentration of chlorophyll within a leaf can be estimated.<ref>{{cite journal | vauthors = Cate TM, Perkins TD | title = Chlorophyll content monitoring in sugar maple (Acer saccharum) | journal = Tree Physiology | volume = 23 | issue = 15 | pages = 1077–9 | date = October 2003 | pmid = 12975132 | doi = 10.1093/treephys/23.15.1077 | doi-access = free }}</ref> Methods also exist to separate [[chlorophyll a|chlorophyll ''a'']] and [[chlorophyll b|chlorophyll ''b'']].

In [[diethyl ether]], chlorophyll ''a'' has approximate absorbance maxima of 430&nbsp;nm and 662&nbsp;nm, while chlorophyll ''b'' has approximate maxima of 453&nbsp;nm and 642&nbsp;nm.<ref>{{cite book | vauthors = Gross J | year = 1991 | title = Pigments in vegetables: chlorophylls and carotenoids | publisher = Van Nostrand Reinhold | isbn = 978-0442006570 }}</ref> The absorption peaks of chlorophyll ''a'' are at 465&nbsp;nm and 665&nbsp;nm. Chlorophyll ''a'' [[fluorescence|fluoresces]] at 673&nbsp;nm (maximum) and 726&nbsp;nm. The peak [[Molar absorptivity|molar absorption coefficient]] of chlorophyll ''a'' exceeds 10<sup>5</sup>&nbsp;M<sup>−1</sup>&nbsp;cm<sup>−1</sup>, which is among the highest for small-molecule organic compounds.<ref>{{Cite journal | vauthors = Porra RJ, Thompson WA, Kriedemann PE |year=1989|title=Determination of accurate extinction coefficients and simultaneous equations for assaying chlorophylls a and b extracted with four different solvents: verification of the concentration of chlorophyll standards by atomic absorption spectroscopy|journal= Biochimica et Biophysica Acta (BBA) - Bioenergetics|volume= 975|issue=3|pages=384–394 |doi=10.1016/S0005-2728(89)80347-0}}</ref> In 90% acetone-water, the peak absorption wavelengths of chlorophyll ''a'' are 430&nbsp;nm and 664&nbsp;nm; peaks for chlorophyll ''b'' are 460&nbsp;nm and 647&nbsp;nm; peaks for chlorophyll ''c<sub>1</sub>'' are 442&nbsp;nm and 630&nbsp;nm; peaks for chlorophyll ''c<sub>2</sub>'' are 444&nbsp;nm and 630&nbsp;nm; peaks for chlorophyll ''d'' are 401&nbsp;nm, 455&nbsp;nm and 696&nbsp;nm.<ref>{{cite book | veditors = Larkum AW, Douglas S, Raven JA | title = Photosynthesis in algae|year=2003|publisher=Kluwer|location=London|isbn=978-0-7923-6333-0}}</ref>

Ratio fluorescence emission can be used to measure chlorophyll content. By exciting chlorophyll ''a'' fluorescence at a lower wavelength, the ratio of chlorophyll fluorescence emission at {{val|705|10|u=nm}} and {{val|735|10|u=nm}} can provide a linear relationship of chlorophyll content when compared with chemical testing. The ratio ''F''<sub>735</sub>/''F''<sub>700</sub> provided a [[correlation coefficient|correlation value of ''r''<sup>2</sup>]] 0.96 compared with chemical testing in the range from 41&nbsp;mg&nbsp;m<sup>−2</sup> up to 675&nbsp;mg&nbsp;m<sup>−2</sup>. Gitelson also developed a formula for direct readout of chlorophyll content in mg&nbsp;m<sup>−2</sup>. The formula provided a reliable method of measuring chlorophyll content from 41&nbsp;mg&nbsp;m<sup>−2</sup> up to 675&nbsp;mg&nbsp;m<sup>−2</sup> with a correlation ''r''<sup>2</sup> value of 0.95.<ref>{{cite journal| vauthors = Gitelson AA, Buschmann C, Lichtenthaler HK |date=1999 |title=The Chlorophyll Fluorescence Ratio ''F''<sub>735</sub>/''F''<sub>700</sub> as an Accurate Measure of Chlorophyll Content in Plants |journal=Remote Sens. Environ. |volume=69 |issue=3 |pages=296–302|doi=10.1016/S0034-4257(99)00023-1 |bibcode=1999RSEnv..69..296G }}</ref>

Also, the chlorophyll concentration can be estimated by measuring the light transmittance through the plant leaves.<ref>{{cite journal | vauthors = Najm AA, Kashani A, Paknejad F, Ardakani MR, Hadi MR |title= Using by rapid field test methods to assess the Potato canopy nitrogen status in the presence of organic and inorganic nitrogen fertilizer|journal= International Journal of Advanced Life Sciences |volume=8 |issue=3|pages=328–339|year=2015|issn=2320-1827|url=https://unitedlifejournals.in/ms_files/ijals/14._Using_rapid_filed_test_methods_to_assess_the_potato_canopy.pdf }}</ref> The assessment of leaf chlorophyll content using optical sensors such as [[Dualex]] and SPAD allows researchers to perform real-time and non-destructive measurements.<ref>{{Cite web | vauthors = Cerovic ZG |title=New proximal sensors of vegetation: towards a non destructive quantitative estimation of plant constituents |url=http://www.ese.u-psud.fr/IMG/pdf/CerovicEbernburg2012.pdf |url-status=dead |archive-url=https://web.archive.org/web/20140822115631/http://www.ese.u-psud.fr/IMG/pdf/CerovicEbernburg2012.pdf |archive-date=2014-08-22 |date=October 2012 |place=Ebernburg |access-date=2024-07-12 }}</ref><ref>{{cite journal | vauthors = Huan YU, Hua-Song WU, Zhi-Jie WA |title= Evaluation of SPAD and Dualex for In-Season Corn Nitrogen Status Estimation |journal= Acta Agronomica Sinic |volume=36 |issue=5|pages=840–847|year=2010| ISSN= 1875-2780|doi=10.1016/S1875-2780(09)60051-1}}</ref> Research shows that these methods have a positive correlation with laboratory measurements of chlorophyll.<ref>{{cite journal | vauthors = Vos J, Bom H |title= Hand-held chlorophyll meter: a promising tool to assess the nitrogen status of potato foliage |journal= Potato Res |volume=36|issue= |pages=301–308 |year=1993|doi=10.1007/BF02361796}}</ref>