Accumulation capacity of ions in cabbage (Brassica oleracea L.) supplied with sea water

Cabbage seedlings were grown hydroponically to study the effects of different concentrations of seawater on the seedling growth, ion content under one-fourth strength Hoagland's nutrient solution in the greenhouse. The biomass of various organs of cabbage seedlings as well as the whole plants was significantly higher in the treatments with 1 g and 2 g sea salt/L than the no-salt control, but the treatments with 4, 5 or 6 g sea salt/L caused a decrease in growth. Root/shoot ratio remained at the level of control regardless of the sea salt treatment. Na+ and Cl- concentration in different parts of cabbage seedlings increased significantly, whereas K+ and Ca2+ concentration generally increased at low concentrations of sea salt and then decreased with increasing seawater concentration. Sodium and K+ concentrations were significantly higher in the stems than roots and leaves regardless of the sea salt treatment. The sea salt treatment increased Mg2+ concentration in stems and leaves of cabbage seedlings. An increase in Na+ and Cl- concentration in roots, stems and leaves of cabbage seedlings was the main contributor to declining ratios of K+/Na+, Ca2+/Na+ and Mg2+/Na+. The obtained data suggest that cabbage seedlings have strong ability to sustain seawater stress by the regulation of transport and distribution of ions

Low PSI content limits the photoprotection of PSI and PSII in early growth stages of chlorophyll b-deficient wheat mutant lines

In vivo analyses of electron and proton transport-related processes as well as photoprotective responses were carried out at different stages of growth in chlorophyll b (Chl b)-deficient mutant lines (ANK-32A and ANK-32B) and wild type (WT) of wheat (Triticum aestivum L.). In addition to a high Chl a-b ratio, ANK mutants had a lower content of photo-oxidizable photosystem I (PSI, P (m)), and several parameters indicated a low PSI/PSII ratio. Moreover, simultaneous measurements of Chl fluorescence and P700 indicated a shift of balance between redox poise of the PSII acceptor side and the PSII donor side, with preferential reduction of the plastoquinone pool, resulting in an over reduced PSI acceptor side (high I broken vertical bar (NA) values). This was the probable reason for PSI inactivation observed in the ANK mutants, but not in WT. In later growth phases, we observed partial relief of "chlorina symptoms," toward WT. Measurements of Delta A (520) decay confirmed that, in early growth stages, the ANK mutants with low PSI content had a limited capacity to build up the transthylakoid proton gradient (Delta pH) needed to trigger non-photochemical quenching (NPQ) and to regulate the electron transport by cytochrome b (6)/f. Later, the increase in the PSI/PSII ratio enabled ANK mutants to reach full NPQ, but neither over reduction of the PSI acceptor side nor PSI photoinactivation due to imbalance between the activity of PSII and PSI was mitigated. Thus, our results support the crucial role of proper regulation of linear electron transport in the protection of PSI against photoinhibition. Moreover, the ANK mutants of wheat showing the dynamic developmental changes in the PSI/PSII ratio are presented here as very useful models for further studies.In vivo analyses of electron and proton transport-related processes as well as photoprotective responses were carried out at different stages of growth in chlorophyll b (Chl b)-deficient mutant lines (ANK-32A and ANK-32B) and wild type (WT) of wheat (Triticum aestivum L.). In addition to a high Chl a-b ratio, ANK mutants had a lower content of photo-oxidizable photosystem I (PSI, P (m)), and several parameters indicated a low PSI/PSII ratio. Moreover, simultaneous measurements of Chl fluorescence and P700 indicated a shift of balance between redox poise of the PSII acceptor side and the PSII donor side, with preferential reduction of the plastoquinone pool, resulting in an over reduced PSI acceptor side (high I broken vertical bar (NA) values). This was the probable reason for PSI inactivation observed in the ANK mutants, but not in WT. In later growth phases, we observed partial relief of "chlorina symptoms," toward WT. Measurements of Delta A (520) decay confirmed that, in early growth stages, the ANK mutants with low PSI content had a limited capacity to build up the transthylakoid proton gradient (Delta pH) needed to trigger non-photochemical quenching (NPQ) and to regulate the electron transport by cytochrome b (6)/f. Later, the increase in the PSI/PSII ratio enabled ANK mutants to reach full NPQ, but neither over reduction of the PSI acceptor side nor PSI photoinactivation due to imbalance between the activity of PSII and PSI was mitigated. Thus, our results support the crucial role of proper regulation of linear electron transport in the protection of PSI against photoinhibition. Moreover, the ANK mutants of wheat showing the dynamic developmental changes in the PSI/PSII ratio are presented here as very useful models for further studies