Pigment identification during deetiolation of barley seedlings

Abstract

Angiosperm plants like barley (Hordeum vulgare) lack chlorophyll when grown in complete dark. Upon exposure to light, chlorophyll is formed during the process of deetiolation. Here , we show that in complete darkness barley seedlings accumulate monovinyl protochlorophyllide. Also small amounts of a second protochlorophyllide form were found. Spectroscopic measurements indicated that the unknown pchlide form is divinyl protochlorophyllide. Upon exposure to light for ten seconds some of MV-protochlorophyllide was photoreduced to MV chlorophyllide while divinyl pchlide remained constant. The loss of chlide and accumulation of chlorophyllide a was determined. Within twenty minutes MV-pchlide concentration was restored , the concentration of chlide was strongly decreased and chl continued to accumulate. Interestingly, exposure of plants to safelight was not capable to phototransform MV-Pchlide. However it resulted in increase in the second protochlide form upon exposure of barley seedlings to light. The finding indicates that the safelight used in the experiment influences capacity of chlorophyll biosynthesis.