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Arabidopsis thaliana SYNAPTOTAGMIN 1 (AtSYT1) was shown to be involved in responses to different environmental and biotic stresses. We investigated gas exchange and chlorophyll a fluorescence in Arabidopsis wild-type (WT, ecotype Col-0) and atsyt1 mutant plants irrigated for 48 h with 150 mM NaCl. We found that salt stress significantly decreases net photosynthetic assimilation, effective photochemical quantum yield of photosystem II (ΦPSII), stomatal conductance and transpiration rate in both genotypes. Salt stress has a more severe impact on atsyt1 plants with increasing effect at higher illumination. Dark respiration, photochemical quenching (qP), non-photochemical quenching and ΦPSII measured at 750 µmol m−2 s−1 photosynthetic photon flux density were significantly affected by salt in both genotypes. However, differences between mutant and WT plants were recorded only for qP and ΦPSII. Decreased photosynthetic efficiency in atsyt1 under salt stress was accompanied by reduced chlorophyll and carotenoid and increased flavonol content in atsyt1 leaves. No differences in the abundance of key proteins participating in photosynthesis (except PsaC and PsbQ) and chlorophyll biosynthesis were found regardless of genotype or salt treatment. Microscopic analysis showed that irrigating plants with salt caused a partial closure of the stomata, and this effect was more pronounced in the mutant than in WT plants. The localization pattern of AtSYT1 was also altered by salt stress. [ABSTRACT FROM AUTHOR]

The aim of this study was to examine the influence of various types and levels of effective microorganism (EM) applications on scarlet sage. For this purpose, EMs were applied at the following three concentrations: 1:10, 1:50, and 1:100. Moreover, two types of treatments (spraying and watering) and a combination of the two were also examined. Photosynthetic intensity was analyzed, including the net photosynthesis rate (PN), stomatal conductance (gS), and intercellular CO2 concentration (Ci). Additionally, chlorophyll a, b, and a + b, and the chlorophyll b/a ratio were analyzed. The microbial content in the medium and soil enzyme activity were also evaluated to examine the effect of EMs on soil biological properties. The investigations revealed a high positive effect of EMs on the photosynthetic activity of most EM combinations compared with the control. The greatest positive effect was noted for the highest EM concentration application for both types of treatments. There was no such influence on soil activity. An increase was noted only in the number of fungi and dehydrogenase activity, while the rest of the soil biological status parameters revealed significant variability, and mostly small or no effects were recorded. [ABSTRACT FROM AUTHOR]

Ferrochelatase (FC) is the terminal enzyme of heme biosynthesis. In photosynthetic organisms studied so far, there is evidence for two FC isoforms, which are encoded by two genes (FC1 and FC2). Previous studies suggest that these two genes are required for the production of two physiologically distinct heme pools with only FC2-derived heme involved in photosynthesis. We characterised two FCs in barley (Hordeum vulgare L.). The two HvFC isoforms share a common catalytic domain, but HvFC2 additionally contains a C-terminal chlorophyll a/b binding (CAB) domain. Both HvFCs are highly expressed in photosynthetic tissues, with HvFC1 transcripts also being abundant in non-photosynthetic tissues. To determine whether these isoforms differentially affect photosynthesis, transgenic barley ectopically overexpressing HvFC1 and HvFC2 were generated and evaluated for photosynthetic performance. In each case, transgenics exhibited improved photosynthetic rate (Asat), stomatal conductance (gs) and carboxylation efficiency (CE), showing that both FC1 and FC2 play important roles in photosynthesis. Our finding that modified FC expression can improve photosynthesis up to ~13% under controlled growth conditions now requires further research to determine if this can be translated to improved yield performance under field conditions. [ABSTRACT FROM AUTHOR]