SOME LIMITATIONS AND POTENTIALITIES OF THE SPECTROPHOTOMETRIC ASSAY OF PIGMENTS EXTRACTED FROM LEAVES OF HIGHER-PLANTS

Spectrophotometric assay of pigments in extracts from plant leaves was revised and data processing was partially modified. For measuring chl orophyll a and b concentrations in plant extracts, the equation A(lamb da)/epsilon(a)(lambda) = C-a + [epsilon(b)(lambda)/epsilon(a)(lambda)] C-b is considered, where A(lambda) is the absorbance spectrum of the e xtract analyzed, C-a and C-b are concentrations of chlorophylls a and b, and epsilon(a)(lambda) and epsilon(b)(lambda) are respective wavele ngth dependencies of the molar extinction coefficients. This equation meets the criterion for a two-component system. In the presence of add itional light-absorbing components, this function deviated from linear ily In the region 550-670 nm, as was the case in the extracts containi ng products of chlorophyll pheophytinization and photodegradation. Thi s approach makes it possible to estimate the analytical error and to a ssess the spectral range of light absorption by impurities. Our data s howed that, in some samples (extracts from pea, sorrel, or senescing m aple leaves), the conventional two-wavelength photometry can lead to s ignificant errors in pigment assays. The aforementioned criterion show ed that, in extracts from wheat seedlings or green leaves of maple and stinging nettle, chlorophyll content can be measured with reasonably high accuracy. Additional qualitative and quantitative information on the compounds present in extracts was obtained by subtracting chloroph yll absorbance spectra from the initial absorbance spectrum. This was demonstrated with extracts containing carotenoids, anthocyanins, and l ong-wavelength UV-absorbing compounds.