Thylakoid Membrane Composition and Photoinactivation of CO2 Fixation in Moss Protonemata as Influenced by the Growth Temperature

Abstract

The effect of the growth temp. on the thylakoid membrane lipid and protein compn. in protonemata of a moss, Ceratodon purpureus was studied and CO2 fixation of the warm- and cold-grown protonemata was compared under different light levels at low temp. Thylakoid membranes of cold-grown protonemata had a markedly higher lipid content than warm-grown ones, whereas the protein content was not significantly affected by growth temp. The lipid compn. of the warm- and cold-grown protonemata differed slightly. The av. no. of double bonds per lipid class increased at low temp.; in mono- and digalactosyldiacylglycerols, a higher amt. of C16:3 fatty acid was typical of cold-grown protonemata. Chloroplast ultrastructure did not reveal as intense thylakoid appression as could be expected on the basis of low chlorophyll a/b ratios (2.2). The most prominent differences in CO2 fixation by warm- and cold-grown protonemata were in their susceptibility to photoinactivation at low temps. and in the recovery where the light level was reduced. [on SciFinder(R)]