Electrical Signaling, Photosynthesis and Systemic Acquired Acclimation

Electrical signaling in higher plants is required for the appropriate intracellular and intercellular communication, stress responses, growth and development. In this review, we have focus on recent findings regarding the electrical signaling, as a major regulator of the systemic acquired acclimation (SAA) and the systemic acquired resistance (SAR). The electric signaling on its own cannot confer the required specificity of information to trigger SAA and SAR, therefore, we have also discussed a number of other mechanisms and signaling systems that can operate in combination with electric signaling. We have emphasized the interrelation between ionic mechanism of electrical activity and regulation of photosynthesis, which is intrinsic to a proper induction of SAA and SAR. In a special way, we have summarized the role of non-photochemical quenching and its regulator PsbS. Further, redox status of the cell, calcium and hydraulic waves, hormonal circuits and stomatal aperture regulation have been considered as components of the signaling. Finally, a model of light-dependent mechanisms of electrical signaling propagation has been presented together with the systemic regulation of light-responsive genes encoding both, ion channels and proteins involved in regulation of their activity. Due to space limitations, we have not addressed many other important aspects of hormonal and ROS signaling, which were presented in a number of recent excellent reviews

Effects of 24-Epibrassinolide, Bikinin, and Brassinazole on Barley Growth under Salinity Stress Are Genotype- and Dose-Dependent

Brassinosteroids (BRs) are involved in the regulation of many plant developmental processes and stress responses. In the presented study, we found a link between plant growth under salinity stress and sensitivity to 24-epibrassinolide (24-EBL, the most active phytohormone belonging to BRs), brassinazole (Brz) and bikinin (inhibitors of BR biosynthesis and signaling pathways, respectively). Plant sensitivity to treatment with active substances and salinity stress was genotype-dependent. Cv. Haruna Nijo was more responsive during the lamina joint inclination test, and improved shoot and root growth at lower concentrations of 24-EBL and bikinin under salinity stress, while cv. Golden Promise responded only to treatments of higher concentration. The use of Brz resulted in significant dose-dependent growth inhibition, greater for cv. Haruna Nijo. The results indicated that BR biosynthesis and/or signaling pathways take part in acclimation mechanisms, however, the regulation is complex and depends on internal (genotypic and tissue/organ sensitivity) and external factors (stress). Our results also confirmed that the lamina joint inclination test is a useful tool to define plant sensitivity to BRs, and to BR-dependent salinity stress. The test can be applied to manipulate the growth and stress responses of crops in agricultural practice or to select plants that are sensitive/tolerant to salinity stress in the plant breeding projects

Effects of 24-Epibrassinolide, Bikinin, and Brassinazole on Barley Growth under Salinity Stress Are Genotype- and Dose-Dependent

Brassinosteroids (BRs) are involved in the regulation of many plant developmental processes and stress responses. In the presented study, we found a link between plant growth under salinity stress and sensitivity to 24-epibrassinolide (24-EBL, the most active phytohormone belonging to BRs), brassinazole (Brz) and bikinin (inhibitors of BR biosynthesis and signaling pathways, respectively). Plant sensitivity to treatment with active substances and salinity stress was genotype-dependent. Cv. Haruna Nijo was more responsive during the lamina joint inclination test, and improved shoot and root growth at lower concentrations of 24-EBL and bikinin under salinity stress, while cv. Golden Promise responded only to treatments of higher concentration. The use of Brz resulted in significant dose-dependent growth inhibition, greater for cv. Haruna Nijo. The results indicated that BR biosynthesis and/or signaling pathways take part in acclimation mechanisms, however, the regulation is complex and depends on internal (genotypic and tissue/organ sensitivity) and external factors (stress). Our results also confirmed that the lamina joint inclination test is a useful tool to define plant sensitivity to BRs, and to BR-dependent salinity stress. The test can be applied to manipulate the growth and stress responses of crops in agricultural practice or to select plants that are sensitive/tolerant to salinity stress in the plant breeding projects

Optimal Design of pH-neutral Geopolymer Foams for Their Use in Ecological Plant Cultivation Systems

We have calculated that with the world population projected to increase from 7.5 billion in 2017 to 9.8 in 2050, the next generation (within 33 years) will produce 12,000–13,000 Mt of plastic, and that the yearly consumption will reach 37–40 kilos of plastic per person worldwide. One of the branches of the plastics industry is the production of plastics for agriculture e.g., seed trays and pots. In this paper, novel metakaolin-based geopolymer composites reinforced with cellulosic fibres are presented as an alternative to plastic pots. Materials can be dedicated to agricultural applications, provided they have neutral properties, however, geopolymer paste and its final products have high pH. Therefore, a two-step protocol of neutralisation of the geopolymer foam pots was optimised and implemented. The strength of the geopolymer samples was lower when foams were neutralised. The reinforcement of geopolymers with cellulose clearly prevented the reduction of mechanical properties after neutralisation, which was correlated with the lower volume of pores in the foam and with the cellulose chemical properties. Both, neutralisation and reinforcement with cellulose can also eliminate an efflorescence. Significantly increased plant growth was found in geopolymer pots in comparison to plastic pots. The cellulose in geopolymers resulted in better adsorption and slower desorption of minerals during fertilisation. This effect could also be associated with a lower number of large pores in the presence of cellulose fibres in pots, and thus more stable pore filling and better protection of internal surface interactions

Biotechnological Potential of LSD1, EDS1, and PAD4 in the Improvement of Crops and Industrial Plants

Lesion Simulating Disease 1 (LSD1), Enhanced Disease Susceptibility (EDS1) and Phytoalexin Deficient 4 (PAD4) were discovered a quarter century ago as regulators of programmed cell death and biotic stress responses in Arabidopsis thaliana. Recent studies have demonstrated that these proteins are also required for acclimation responses to various abiotic stresses, such as high light, UV radiation, drought and cold, and that their function is mediated through secondary messengers, such as salicylic acid (SA), reactive oxygen species (ROS), ethylene (ET) and other signaling molecules. Furthermore, LSD1, EDS1 and PAD4 were recently shown to be involved in the modification of cell walls, and the regulation of seed yield, biomass production and water use efficiency. The function of these proteins was not only demonstrated in model plants, such as Arabidopsis thaliana or Nicotiana benthamiana, but also in the woody plant Populus tremula x tremuloides. In addition, orthologs of LSD1, EDS1, and PAD4 were found in other plant species, including different crop species. In this review, we focus on specific LSD1, EDS1 and PAD4 features that make them potentially important for agricultural and industrial use

Variation Among Spring Wheat (Triticum aestivum L.) Genotypes in Response to the Drought Stress. II—Root System Structure

(1) Background: The study analyzed wheat morphological traits to assess the role of roots structure in the tolerance of drought and to recognize the mechanisms of root structure adjustment to dry soil environment. (2) Methods: Root-box and root-basket methods were applied to maintain an intact root system for analysis. (3) Results: Phenotypic differences among six genotypes with variable drought susceptibility index were found. Under drought, the resistant genotypes lowered their shoot-to-root ratio. Dry matter, number, length, and diameter of nodal and lateral roots were higher in drought-tolerant genotypes than in sensitive ones. The differences in the surface area of the roots were greater in the upper parts of the root system (in the soil layer between 0 and 15 cm) and resulted from the growth of roots of the tolerant plant at an angle of 0–30° and 30–60°. (4) Conclusions: Regulation of root bending in a more downward direction can be important but is not a priority in avoiding drought effects by tolerant plants. If this trait is reduced and accompanied by restricted root development in the upper part of the soil, it becomes a critical factor promoting plant sensitivity to water-limiting conditions