SOME ABSORPTION SPECTRA OF LEAF EXTRACTS

Abstract

This study was originated in an attempt to account for the visible difference in appearance of toluenized leaves dried in air and in hydrogen. It was extended to include several other methods of leaf-killing, to determine the significance of changes noted in the absorption spectra of the leaf extracts. Marked differences, dependent upon the method of preparation of extracts, have been noted by Strain (5) for certain of the xanthophyll components, and it was thought that equally striking changes in the chlorophyll components might be found. Because many of these differences can be ascertained only by the use of an adsorbent, adsorption studies have been made to supplement the spectroscopic data. Few methods of adsorption?none, so far, to the writer's knowledge, for plant pigments?are adequate for detecting quantitatively the differences in the ratios of the various components for a leaf under study. In spite of this drawback, the adsorbent furnishes a useful check on changes which may take place in the pigment complex, and in many instances prevents differences in the spectroscopic data from being ascribed to wholly erroneous causes. Inulin has been found in this laboratory to be an extremely useful adsorbent for separating the a and b components of chlorophyll from crude leaf extracts in petroleum ether. It has two apparent advantages over sucrose, its markedly lower hygroscopicity and the fact that purification of the leaf extracts is unnecessary.