A possible structural role for carotenoids and carotenoid precursors in etioplasts

Seedlings of wheat (Triticum aestivum L.) were grown in darkness in different concentrations of the herbicide SAN‐9789, an inhibitor of carotenoid synthesis. The ultrastructural appearance of etioplasts, containing different amounts of carotenoids, was compared to the contents of carotenoids and carotenoid precursors (phytoene and phytofluene). A correlation was found between the presence of carotenoids and the presence of partitions between prothylakoids. As the plants were grown in darkness, this correlation is interpreted as the result of a structural role of the carotenoids. The presence of the herbicide SAN‐9789 resulted in an increase in size and a change from osmiophilic to non‐osmiophilic plastoglobuli. This change in plastoglobuli was neither correlated to the increase in phytoene or phytofluene, nor to the decrease in carotenoids.