Real-Time Imaging of Leaf Apoplastic pH Dynamics in Response to NaCl Stress

Knowledge concerning apoplastic ion concentrations is important for the understanding of many processes in plant physiology. Ion-sensitive fluorescent probes in combination with quantitative imaging techniques offer opportunities to localize, visualize, and quantify apoplastic ion dynamics in situ. The application of this technique to the leaf apoplast is complicated because of problems associated with dye loading. We demonstrate a more sophisticated dye loading procedure that enables the mapping of spatial apoplastic ion gradients over a period of 3 h. The new technique has been used for the real-time monitoring of pH dynamics within the leaf apoplast in response to NaCl stress encountered by the roots

Plant-derived sulfur containing natural products produced as a response to biotic and abiotic stresses: A review of their structural diversity and medicinal importance

Plant-derived sulfur-containing secondary metabolites constitute a small group of low-molecular weight natural products, which play a vital role in plant-pest interactions in numerous plant families andrepresent major defense molecules in the Asteraceae, Alliaceae, and Brassicaceae families. In this review we highlight the crucial role of environmental stress factors in the production of S-containing secondary metabolites. Furthermore, we describe a serendipitous variety of plant-derived sulfur-containing natural products produced or induced under biotic and abiotic stress and their structural diversity, promising pharmacological properties for use by humans, and beneficial effects for plants. Specifically, cruciferous phytoalexins are known as elicit plant defense molecules. Glucosinolates are candidates for tumorpreventive effects. Cysteine sulfoxides found in garlic are considered as profound antimicrobial agents. In this review, we discuss types of S bonds in the molecules and their relevance for the medicinal effect as well as the biological activities of sulfur-containing secondary metabolites and possible future avenues

Comparative Effectiveness of Four Nitrification Inhibitors for Mitigating Carbon Dioxide and Nitrous Oxide Emissions from Three Different Textured Soils

Nitrification inhibitors (NIs) can be used to reduce both NO3−-N leaching and N2O-N emissions. However, the comparative efficacies of NIs can be strongly affected by soil type. Therefore, the efficacies of four nitrification inhibitors (dicyandiamide (DCD), 3, 4-dimethylpyrazole phosphate (DMPP), nitrogenous mineral fertilizers containing the DMPP ammonium stabilizer (ENTEC) and active ingredients: 3.00–3.25% 1, 2, 4-triazole and 1.50–1.65% 3-methylpyrazole (PIADIN)) were investigated in three different textured N-fertilized (0.5 g NH4+-N kg−1 soil) soils of Schleswig-Holstein, namely, Marsch (clayey), Östliches Hügelland (loamy) and Geest (sandy) under a controlled environment. Total CO2-C and N2O-N emissions were significantly higher from Marsch than Östliches Hügelland and Geest. In Marsch, DMPP showed the highest inhibitory effect on CO2-C emission (50%), followed by PIADIN (32%) and ENTEC (16%). In Östliches Hügelland, DCD and PIADIN showed the highest and equal inhibitory effect on CO2-C emission (73%), followed by DMPP (64%) and ENTEC (36%). In Marsch and Östliches Hügelland, DCD showed the stronger inhibitory effect on N2O-N emission (86% and 47%) than DMPP (56% and 30%) and PIADIN (54% and 16%). In Geest, DMPP was more effective in reducing N2O-N emission (88%) than PIADIN (70%) and DCD (33%). Thus, it can be concluded that DCD is a better NI for clay and loamy soils, while DMPP and PIADIN are better for sandy soils to inhibit soil nitrification and gaseous emissions

Biofortification and subcellular localization of minerals in faba bean as influenced by Mg foliar application

Foliar application of Mg is a measure for the correction of Mg deficiency in crop plants. Foliar applied nutrients need to access the symplastic side where majority of physiological processes take place. To achieve an adequate uptake of the Mg ions through the leaf surface, high concentrations of of 100-200 mM MgSO4 are usually supplied. This can cause antagonistic perturbations on the subcellular distribution of Caand K cations. To test for such unintended side effects, we used the infiltration-centrifugation method to extract ions from the apoplastic and symplastic side of Vicia faba leaves and quantified concentrations of Mg, Ca and K in dependency to the dose of the foliar fertilized Mg. Results show that a large fraction of Mg accesses the symplast whereas the apoplastic fraction shows a concomitant increase. Symplastic and apoplastic K and Ca relations were only affected under conditions of high exogenous leaf supply of Mg (200 mM) but did not change upon moderate Mg supply (50; 100 mM). Overall, results reveal the suitability of leaf fertilization to biofortify plant-based products with magnesium. With respect to human nutrition, care must be taken that K and Ca do not become impoverished based on antagonistic effects

Sulfur but not nitrogen supply increases the ITC/Nitrile ratio in Pak Choi (Brassica rapa subsp. chinensis (L.) Hanelt)

Glucosinolates (GLS) are a serendipitous class of secondary metabolites found in pak choi, a Chinese cabbage (Brassica rapa subsp. chinensis (L.) Hanelt). GLS are hydrolyzed by the enzyme myrosinase to obtain isothiocyanates (ITC), nitriles, and epithionitriles. GLS hydrolysis products (GLS-HP) are responsible for the typical flavor and odour of pak choi. Little is known about the influence of S and N interactions on pak choi GLS and their hydrolysis products (GLS-HP), especially nitriles.We investigated the effect of S and N concentrations on pak choi GLS, isothiocyanates, and nitriles content under varying nitrogen (0.75 and 1.5 g N pot–1) and sulfur (0, 0.06, and 0.3 g S pot–1) supply. Increasing the S supply but not N resulted in a reciprocal increase of the total GLS. The GLS concentration decreased under S deficiency. S supply delivered an optimized GLS pattern, and substantially enhanced the synthesis of aliphatic GLS and ITC in particular. In contrast, N-rich nutrition favored the synthesis of indolic GLS and nitriles, the latter are known to have less health beneficial potential and even showed harmful effects. The study indicates, for the first time, that the ITC/nitrile ratio increases under S supply.GLS and their GLS degradation products in pak choi showed a strong response to sulfur supply. Moreover, the ITC/nitrile ratio might be used as a physiological trait to compare nutritional quality and health benefits of brassica species

Regulation of Selenium/Sulfur Interactions to Enhance Chemopreventive Effects: Lessons to Learn from Brassicacrassiceae

Selenium (Se) is an essential trace element, which represents an integral part of glutathione peroxidase and other selenoproteins involved in the protection of cells against oxidative damage. Selenomethionine (SeMet), selenocysteine (SeCys), and methylselenocysteine (MeSeCys) are the forms of Se that occur in living systems. Se-containing compounds have been found to reduce carcinogenesis of animal models, and dietary supplemental Se might decrease cancer risk. Se is mainly taken up by plant roots in the form of selenate via high-affinity sulfate transporters. Consequently, owing to the chemical similarity between Se and sulfur (S), the availability of S plays a key role in Se accumulation owing to competition effects in absorption, translocation, and assimilation. Moreover, naturally occurring S-containing compounds have proven to exhibit anticancer potential, in addition to other bioactivities. Therefore, it is important to understand the interaction between Se and S, which depends on Se/S ratio in the plant or/and in the growth medium. Brassicaceae (also known as cabbage or mustard family) is an important family of flowering plants that are grown worldwide and have a vital role in agriculture and populations' health. In this review we discuss the distribution and further interactions between S and Se in Brassicaceae and provide several examples of Se or Se/S biofortifications' experiments in brassica vegetables that induced the chemopreventive effects of these crops by enhancing the production of Se- or/and S-containing natural compounds. Extensive further research is required to understand Se/S uptake, translocation, and assimilation and to investigate their potential role in producing anticancer drugs

Foliar Magnesium supply increases the abundance of RuBisCO of Mg-deficient maize plants

Magnesium is a vital macronutrient for plants and is involved in a series of essential physiological processes, e.g., carbohydrate partitioning and photosynthesis. The latter is strictly Mg-dependent, as Mg is the central atom of chlorophyll, and is also required for the de novo synthesis of sugars; this pathway revolves around the activity of the enzyme RuBisCO. When plants are subject to Mg limiting conditions, development as well as yield is reduced. The foliar resupply of Mg, contrary to traditional resupply to the roots, has the advantage of delivering the element directly to the site of highest physiological demand. Thus, the aim of this research is to compare the effects of both resupply methods on the physiology and nutritional status of Mg-deficient plants to see whether foliar application compared to root fertilization can properly improve plant growth after Mg deficiency conditions.Maize plants were cultivated in hydroponics in order to set up a Mg deficient root environment. MgSO4 was then resupplied alternatively to the leaves or to the root. Under Mg-limiting conditions, RuBisCO abundance, as well as the total content of Mn, Zn, Fe, and Cu were severely reduced. This state was significantly ameliorated by the foliar resupply of MgSO4, although the highest increase in biomass production was observed in response to root resupply. The foliar resupply of MgSO4 upregulated the process of photosynthesis in Mg-deprived plants. In this context, the foliar MgSO4 application was able to return RuBisCO abundance to control levels in Mg-deficient plants

One-time abscisic acid priming induces long-term salinity resistance in Vicia faba: Changes in key transcripts, metabolites, and ionic relations

Abscisic acid (ABA) priming is known to enhance plant growth and survival under salinity. However, the mechanisms mediating this long-term acclimatization to salt stress are still obscure. Specifically, the long-term transcriptional changes and their effects on ion relations were never investigated. This motivated us to study the long-term (8 days) effect of one-time 24 h root priming treatment with 10 μM ABA on transcription levels of relevant regulated key genes, osmotically relevant metabolites, and ionic concentrations in Vicia faba grown under 50 mM NaCl salinity. The novelty of this study is that we could demonstrate long-term effects of a one-time ABA application. ABA-priming was found to prevent the salt-induced decline in root and shoot dry matter, improved photosynthesis, and inhibited terminal wilting of plants. It substantially increased the mRNA level of AAPK and 14-3-3 ABA inducible kinases and ion transporters (PM H+ -ATPase, VFK1, KUP7, SOS1, and CLC1). These ABA-induced transcriptional changes went along with altered tissue ion patterns. Primed plants accumulated less Na+ and Cl- but more K+ , Ca2+ , Zn2+ , Fe2+ , Mn2+ , NO3 - , and SO4 2- . Priming changed the composition pattern of organic osmolytes under salinity, with glucose and fructose being dominant in unprimed, whereas sucrose was dominant in the primed plants. We conclude that one-time ABA priming mitigates salt stress in Vicia faba by persistently changing transcription patterns of key genes, stabilizing the ionic and osmotic balance, and improving photosynthesis and growth