Linolenic Acid and Changes in Absorption of Chloroplasts

The addition of linolenic acid to chloroplasts and sub-chloroplast particles has pronounced effect on light induced absorption changes. At a concentration of 10 —4 M linolenic acid or [LINO]/ [CHL]?«2 (on a mole to mole basis) spectral changes associated with System II are diminished to 50 percent. In this same range there is also a small increase in the spectral change ascribed to System I ; this increase may reflect the action of linolenic acid in uncoupling phosphorylation. While at [LINO]/[CHL]~ 4, light induced absorption changes of System II are completely blocked, there seems to be no inhibition of System I. The effects of linolenic acid on the 515 nm spectra) change are interpreted as an increase in the permeability of the thylakoid membrane.