Evidence of chlorophyll synthesis pathway alteration in desiccated barley leaves

In etiolated leaves, saturating flash of 200 ms induces phototransformation of protochlorophyllide (Pchlide) F655 into chlorophyllide (Chlide), then i nto Chi through reactions which do not need light sensibilisation, The synt hesis of Chi is known to be slowed down in etiolated leaves exposed to desi ccation stress. In order to analyse the intensity and time-course of Chlide transformation into Chi, we used the fluorescence emission of etiolated le aves previously exposed to a 200 ms saturating flash. We used low-temperatu re fluorescence spectroscopy to reveal the inhibition site of Chi synthesis in etiolated barley leaves exposed to water stress. Shibata shift appears as the main target point of the water deficit. It was found that water defi cit inhibits partially active Pchlide F655 regeneration. Also, esterificati on of Chlide into Chi is impaired. It appears that these inhibitory effects alter the appearance of PSII active reaction centres.