Biological variability in the ratios of protochlorophyllide forms in leaves and epicotyls of dark-grown pea (Pisum sativum L.) seedlings (a statistical method to resolve complex spectra)

Low-temperature (77K) fluorescence emission spectra of 100 dark-grown pea (Pisum sativum L.) seedlings of various ages were measured. The spectra of the 100 leaf samples were collected into a separate data group and those of epicotyls formed another one. This group was divided into three sub-groups as spectra of uppermost, middle and lowermost 3 cm sections. Further sub-groups were formed on the basis of the ages of the plants. The spectra were normalized to their total integral values (within the 580-780 nm region) then the AVERAGE (arithmetic mean function) and AVEDEV (average of the absolute deviations of data points of their mean function) spectra were calculated. Very sharp bands were found in the AVEDEV spectra. Even the strongly overlapped 629 and 636 nm emission bands appeared as separate peaks, due to the decrease of their half-bandwidth values in the AVEDEV function. Both types of spectra were resolved into Gaussian components. The results showed that the variabilities of the 633 and 655 nm protochlorophyllide forms were similar in the leaves. In epicotyls, the protochlorophyllide forms had different variabilities, especially in the middle sections. The most variable was the amplitude of the 636 nm band and the variabilities of the 629 and 655 nm bands were smaller but still remarkable. The calculation of AVEDEV spectra is an effective method to study the biological variability and spectral resolution of biological samples containing chromophores with multiple spectral properties.