Evaluation of a portable chlorophyll optical meter to estimate chlorophyll concentration in the green seaweed Ulva ohnoi
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Evaluation of a portable chlorophyll optical meter to estimate chlorophyll concentration in the green seaweed Ulva ohnoi Ingrid Masaló 1
&
Joan Oca 1
Received: 4 July 2020 / Revised and accepted: 10 September 2020 # Springer Nature B.V. 2020
Abstract In situ measurement of chlorophyll concentration, with an optical meter, in the green seaweed Ulva ohnoi is presented to estimate the absolute chlorophyll content. The MC-100 optical meter (Apogee Instruments) was used during the study; the optical meter gives chlorophyll content in relative units as Chlorophyll Content Index units (CCI). Absolute chlorophyll content, in μmol m−2, was determined by extraction with dimethylformamide, and the chlorophyll concentration was measured with a spectrophotometer. Equations to convert CCI from optical meter to absolute chlorophyll content were presented for total chlorophyll, chlorophyll a, and chlorophyll b. Highly linear relationships (r2 above 0.9, n = 130) were found for total chlorophyll, chlorophyll a, and chlorophyll b. In situ non-destructive estimation of U. ohnoi chlorophyll content using the MC-100 portable chlorophyll optical meter was considered convenient, fast, and accurate. Keywords Ulva ohnoi . Chlorophyta . Chlorophyll content . Optical meter
Introduction Pigments are colorful chemical compounds that reflect light of a specific wavelength and absorb other wavelengths. Chlorophyll a and b are green photosynthetic pigments found in plants, algae, and cyanobacteria, which absorb light wavelengths in the visible spectrum. Chlorophyll is vital for photosynthesis, since it traps the light energy from the sun. This light energy is used to combine carbon dioxide and water into sugars in the process of photosynthesis. Many biotic and abiotic stresses cause leaf bleaching, which results from a loss of chlorophyll. Then, chlorophyll content in plants and algae are an important parameter in any research. These studies require the in vitro pigment extraction with organic solvents, and spectrophotometric readings at different wavelengths; finally, the absolute concentration of chlorophyll is determined by different model equations (Porra et al. 1989; Wellburn 1994). The most used organic solvents are acetone 80%, chloroform, diethyl-ether, dimethyl
* Ingrid Masaló [email protected] 1
Departament d’Enginyeria Agroalimentària i Biotecnologia, Universitat Politècnica de Catalunya-BarcelonaTECH, Esteve Terrades 8, 08860 Castelldefels, Catalunya, Spain
formamide DMF, dimethyl sulfoxide DMSO, and methanol. Excepting DMF and DMSO, the other solvents require grinding of the tissue for complete extraction. This extractive method is destructive and laborious and includes hazardous compounds and also requires trained personnel. Non-destructive, in situ, optical techniques, which give a relative value of chlorophyll per unit of area of a leaf, have been used in terrestrial crops with high correlation coefficients between the optical (in situ) and the extractive method (in vitro) chlorophyll relationship (Parry et al. 2014).
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