Chloroplasts were isolated from primary leaves of wheat 12 days after germination and incubated at 25° for 45 min in the dark with soybean lipoxygenase-1. The lipoxygenase action was evident from a weak oxygen uptake of ca 0.18, μmol/hr per mg chloroplast protein. The lipoxygenase treatment caused a marked decrease in the photochemical activity, as measured by the reduction rate of 2,6-dichlorophenolindophenol. However, both the content and composition of the lipids as well as those of total fatty acids remained largely unchanged except for a slight but significant decrease in the total linolenic acid content. It is proposed that soybean lipoxygenase-1 selectively attacks free linolenic acid present in chloroplasts, followed by a chlorophyll-catalysed reaction of hydroperoxylinolenic acid with components of the electron transfer system.
Using a measuring system for PS II with DCPIP as acceptor and DBMIB as plastoquinone inhibitor we found that in isolated chloroplasts from some species of the genus Triticum and Aegilops the activity of PS II alone exceeds that one of the whole chain as well as of PS I alone.
Preliminary results indicated the existence of a DCMU-resistant photosynthetic electron transport. Additional experiments were made to characterise the photochemical activity in isolated chloroplasts as well as the gas exchange and pigment content of primary leaves of Triticum aestivum, treated with DCMU during greening and in the fully greened state, respectively. In the light etiolated Triticum leaves are able to develop an active photosynthetic apparatus in the presence of DCMU but as in green treated leaves — the photochemical activity and chlorophyll content are reduced. Analyzing the electron transport in chloroplasts of Triticum aestivum and 8 selected evolutionary forms of wheat under influence of different concentrations of DCMU, we found a resistant electron transport component in every case. It is discussed as a possible bypath via cyt b559 regulating the direct electron transfer from the acceptor side of PS II to DCPIP.
Preliminary results indicated the existence of a DCMU-resistant photosynthetic electron transport. Additional experiments were made to characterise the photochemical activity in isolated chloroplasts as well as the gas exchange and pigment content of primary leaves of Triticum aestivum, treated with DCMU during greening and in the fully greened state, respectively. In the light etiolated Triticum leaves are able to develop an active photosynthetic apparatus in the presence of DCMU but as in green treated leaves — the photochemical activity and chlorophyll content are reduced. Analyzing the electron transport in chloroplasts of Triticum aestivum and 8 selected evolutionary forms of wheat under influence of different concentrations of DCMU, we found a resistant electron transport component in every case. It is discussed as a possible bypath via cyt b559 regulating the direct electron transfer from the acceptor side of PS II to DCPIP.
