Unexpected Effects of Sulfate and Sodium Chloride Application on Yield Qualitative Characteristics and Symmetry Indicators of Hard and Soft Wheat Kernels

The heterogeneity of grain quality can lead to limited predictability of qualitative and quantitative characteristics of the wheat yield, especially with an increase in the importance of drought and salinity caused by climate change. This study was undertaken with the aim of creating basic tools for phenotyping and assessing the sensitivity of genotypes to salt effects at the level of some wheat kernel attributes. The study considers 36 variants of the experiment, including four wheat cultivars-Zolotaya, Ulyanovskaya 105, Orenburgskaya 10, Orenburgskaya 23; three treatment variants-control (without salt) and two salts exposure (NaCl at a concentration of 1.1 g L^-1 and Na₂SO₄ at a concentration of 0.4 g L^-1); as well as three options for the arrangement of kernels in a simple spikelet-left, middle, and right. It has been established that the salt exposure had a positive effect on the percentage of kernel fulfilling in the cultivars Zolotaya, Ulyanovskaya 105, and Orenburgskaya 23 compared to control. The kernels of the Orenburgskaya 10 variety matured better in the experiment with Na₂SO₄ exposure, while the control variant and NaCl gave the same effect. When exposed to NaCl, significantly greater values of weight, transverse section area, and transverse section perimeter of the kernel were noted in the cv Zolotaya and Ulyanovskaya 105. Cv Orenburgskaya 10 responded positively to the use of Na₂SO₄. This salt caused an increase in the area, length, and width of the kernel. The fluctuating asymmetry of the left, middle, and right kernels in the spikelet was calculated. In the cv Orenburgskaya 23 the salts affected only the kernel perimeter among parameters examined. The indicators of the general (fluctuating) asymmetry were lower in the experiments with the use of salts, i.e., kernels were more symmetrical than in the control variant, both for the cultivar as a whole and when compared taking into account the kernel location in spikelet. However, this result was unexpected, since salt stress inhibited a number of morphological parameters: the number and average length of embryonic, adventitious, and nodal roots, flag leaf area, plant height, dry biomass accumulation, and plant productivity indicators. The study showed that low concentrations of salts can positively affect the fulfilling of kernels (the absence of a cavity inside the kernel) and the symmetry of the left and right sides of the kernel.

Cell and chloroplast anatomical features are poorly estimated from 2D cross-sections

Leaf function is intimately related to the size, shape, abundance and position of cells and chloroplasts. Anatomy has long been assessed and quantified in two dimensions with 3D structure inferred from 2D micrographs. Serial block face scanning electron microscopy (SBF-SEM) was used to reconstruct 95 cells and 1173 chloroplasts from three wheat and nine chickpea leaves (three samples each from three chickpea genotypes). Wheat chloroplast volume was underestimated by 61% in mesophyll cells and 45% in bundle sheath cells from 2D micrographs, whereas chickpea mesophyll chloroplast volume was underestimated by 60% using simple geometrical models. Models of chickpea spongy and palisade cells both under- and overestimated surface area and volume by varying degrees. These models did not adequately capture irregular shapes such as flattening of chloroplasts or lobed spongy mesophyll cells. It is concluded that simple geometrical models to estimate chloroplast and cell 3D volume and surface area from 2D micrographs are inadequate, and that SBF-SEM has strong potential to contribute to improved understanding of leaf form and function.

Foliar application of selenium for protection against the first stages of mycotoxin infection of crop plant leaves

BACKGROUND

The aim of this study was to investigate whether the application of selenium (Se) ions directly to the leaf surface can protect plants against infection by the fungal toxin zearalenone (ZEA). The experiments were performed for the most common and agronomically important crops such as wheat, oat, and barley (both tolerant and sensitive varieties) because mycotoxin accumulation in plants is the cause of many diseases in animals and people.

RESULTS

ZEA at a concentration of 10 µmol L^-1 either alone or in combination with Se (5 µmol L^-1 Na₂ SeO₄ ) was applied to the second leaf of seedlings. Visualization of leaf temperature profiles by infrared thermography demonstrated a decrease in temperature at the location of ZEA infection that was more noticeable in sensitive genotypes. The presence of Se significantly suppressed changes at the site of ZEA application in all tested plants, especially the tolerant genotypes. Microscopic observations confirmed that foliar administration of ZEA resulted in its penetration to deeper localized cells and that damage induced by ZEA (mainly to chloroplasts) decreased after Se application. Analyses of antioxidant enzymes demonstrated the involvement of Se in antioxidation mechanisms, in particular by activating SOD and CAT under ZEA-induced stress conditions.

CONCLUSION

The foliar application of Se to seedling leaves may be a non-invasive method of protecting crops against the first steps of ZEA infection. © 2018 Society of Chemical Industry.

Mechanisms of Sodium Transport in Plants-Progresses and Challenges

Understanding the mechanisms of sodium (Na⁺) influx, effective compartmentalization, and efflux in higher plants is crucial to manipulate Na⁺ accumulation and assure the maintenance of low Na⁺ concentration in the cytosol and, hence, plant tolerance to salt stress. Na⁺ influx across the plasma membrane in the roots occur mainly via nonselective cation channels (NSCCs). Na⁺ is compartmentalized into vacuoles by Na⁺/H⁺ exchangers (NHXs). Na⁺ efflux from the plant roots is mediated by the activity of Na⁺/H⁺ antiporters catalyzed by the salt overly sensitive 1 (SOS1) protein. In animals, ouabain (OU)-sensitive Na⁺, K⁺-ATPase (a P-type ATPase) mediates sodium efflux. The evolution of P-type ATPases in higher plants does not exclude the possibility of sodium efflux mechanisms similar to the Na⁺, K⁺-ATPase-dependent mechanisms characteristic of animal cells. Using novel fluorescence imaging and spectrofluorometric methodologies, an OU-sensitive sodium efflux system has recently been reported to be physiologically active in roots. This review summarizes and analyzes the current knowledge on Na⁺ influx, compartmentalization, and efflux in higher plants in response to salt stress.