Low temperature absorption spectroscopy of barley mutants. Guassian deconvolution and fourth derivative analysis

Abstract

The absorption spectra of wild type barley and a number of nuclear gene mutants have been recorded at 77 K, and analysed by taking the fourth derivative and Gaussian deconvolution in the region 600-725 nm. Seven Gaussian curves could be fitted, corresponding to the Qy transitions of at least 7 different chlorophyll species, absorbing at 640.5 and 649.9 nm (chlorophyll b), 660.7, 668.9, 676.6, 682.9 and 688.9 nm (chlorophyll a). The first 2 components were missing from the chlorophyll b-less mutant clo-f22800, revealing a minor chlorophyll a species at 653 nm. The same 7 wild type components could also be fitted to the low temperature absorption spectra of the mutants vir-m29 and vir-k23. The loss of photosystem II from the mutant vir-115 was associated with the specific loss of the 683 nm component, corresponding to about 30-40 molecules of chlorophyll a per 500 molecules of chlorophyll. Similarly, the absence of photosystem I from the mutant vir-zb63 was correlated with the loss of 30 molecules of chlorophyll a absorbing at 689 nm. These specific differences were confirmed by the absorption difference spectra and by fourth derivative spectroscopy. The validity of the solutions provided by Gaussian deconvolution were evaluated by comparing their fourth derivative with that of the original spectra. © 1988 Carlsberg Laboratory.