<p>This investigation has been performed on Norflurazon (NF) treated young wheat plants with</p><p>emphasis on their capacity to perform light-driven photosynthesis, as an effect of carotenoid </p><p>deficiency. The wheat seeds were soaked for approximately 17 hour in tap water or in water containing NF (28mg l-1 ca 10-4 M). Seedlings were grown for 7 days in a greenhouse (50 μmol m-2 s-1) or in weak light (ca 0.1 μmol m-2 s-1) in order to avoid photodestruction, before chloroplast and thylakoid isolation. NF-treatment and the low light condition also affected chlorophyll content. Isolated chloroplasts from NF-grown plants contained approximately 55 and 16 % of the chlorophyll content as compared to untreated plants grown in weak light or in greenhouse light, respectively. </p><p>In addition, protein separation by polyacryl amide electrophoresis (SDS-PAGE) on isolated thylakoids showed that the apoproteins of the LHC II (i.e. LHCP) were undetectable after NF-treatment. Despite a large number of attempts to measure PS II activity in isolated thylakoids, this was proven to give unreliable data and these were therefore excluded from this report.</p><p>The photosynthetic assays were therefore focused on PS I activity, which were compared between plants grown in greenhouse (untreated) or in weak light, with or without NF. As expected, PSI activity is greatly affected by light intensity, during growth as well as during the photosynhtetic assays. In untreated wheat, grown in the greenhouse, the highest activity was found at the strongest light intensity used at distance of 0.25 m from the light source (corresponding to approximately 1440µmol m-2s-1). The PS I activity then declines with decreasing intensity. A similar, albeit not so clear (lower maximum activity at strong light intensities), trend is observed in untreated wheat grown in weak light.</p><p>Thylakoids isolated from NF-treated plants show a clear photoinhibition at strong light but a clear increase in activity at subsequently lower light intensities.</p>

This investigation has been performed on Norflurazon (NF) treated young wheat plants with emphasis on their capacity to perform light-driven photosynthesis, as an effect of carotenoid deficiency. The wheat seeds were soaked for approximately 17 hour in tap water or in water containing NF (28mg l-1 ca 10-4 M). Seedlings were grown for 7 days in a greenhouse (50 μmol m-2 s-1) or in weak light (ca 0.1 μmol m-2 s-1) in order to avoid photodestruction, before chloroplast and thylakoid isolation. NF-treatment and the low light condition also affected chlorophyll content. Isolated chloroplasts from NF-grown plants contained approximately 55 and 16 % of the chlorophyll content as compared to untreated plants grown in weak light or in greenhouse light, respectively. In addition, protein separation by polyacryl amide electrophoresis (SDS-PAGE) on isolated thylakoids showed that the apoproteins of the LHC II (i.e. LHCP) were undetectable after NF-treatment. Despite a large number of attempts to measure PS II activity in isolated thylakoids, this was proven to give unreliable data and these were therefore excluded from this report. The photosynthetic assays were therefore focused on PS I activity, which were compared between plants grown in greenhouse (untreated) or in weak light, with or without NF. As expected, PSI activity is greatly affected by light intensity, during growth as well as during the photosynhtetic assays. In untreated wheat, grown in the greenhouse, the highest activity was found at the strongest light intensity used at distance of 0.25 m from the light source (corresponding to approximately 1440µmol m-2s-1). The PS I activity then declines with decreasing intensity. A similar, albeit not so clear (lower maximum activity at strong light intensities), trend is observed in untreated wheat grown in weak light. Thylakoids isolated from NF-treated plants show a clear photoinhibition at strong light but a clear increase in activity at subsequently lower light intensities.

No description available.