Comparison of Chlorophyll Accumulation and ¹⁴C-ala Incorporation into Chlorophyll in Dark and Light in Green Barley

Abstract

Light-independent chlorophyll (chl) synthesis has been observed in angiosperm seedlings (1–8), developing and mature leaves of established plants (9, 10) and tissue culture (11). In each case, chl continued to accumulate when plants or tissues which had been exposed to light during their development were returned to darkness. The incorporation of radioactive precursors into chl in darkness has also been observed (12), however in the absence of evidence that label is in the tetrapyrrole moiety this does not necessarily indicate synthesis via a light-independent route. Recently we have demonstrated the incorporation of C-amino levulinic acid (ALA) into the tetrapyrrole nucleus as well as the ester groups of chl a in young barley seedlings returned to darkness (13). The chl accumulation and precursor incorporation experiments reported here were carried out to investigate the extent to which dark chl synthesis contributes to the total chl pool in young barley seedlings growing in a diurnal environment.