Accumulation of phytoene in plastoglobuli of SAN‐9789 (Norflurazon)‐treated dark‐grown wheat

Abstract

Grains of wheat ( Triticum aestivum L. cv. Starke II) were treated with SAN‐9789 (Norflurazon), and grown in darkness for 6 days. The SAN treatment resulted in an inhibition of the carotenoid synthesis at the level of phytoene. The plastids of SAN‐treated plants contained enlarged and non‐osmiophilic plastoglobuli, compared to the plastoglobuli of the control. The plastoglobuli were isolated and purified by means of a flotation technique, and their lipid composition was determined. Efforts were made to avoid contamination of epicuticular soluble lipids in the plastoglobuli suspension during isolation. The most suitable method was found to be a mechanical removal of the lipids from the surface of the intact leaves prior to homogenization. Membrane lipids, i.e. galacto‐, phospho‐ and sulpholipids could not be detected in plastoglobuli from either SAN‐treated or control plants, indicating that contamination with membranes was negligible. In plastoglobuli of SAN‐treated plants, large amounts of phytoene and, to a lesser extent, phytofluene accumulated. The proportion of triacylglycerols to quinones was lower than in the control. The main lipids in control plastoglobuli were triacylglycerols, plastoquinones and α‐tocopherol. The possible function of plastoglobuli in etioplasts is discussed.