Roots Of Barley Plants Research Articles

Short-Term Pretreatment with Melatonin Increases the Resistance of Barley Plants to the Subsequent Action of Cadmium

The effect of short-term and long-term root treatment with melatonin on growth parameters, photochemical activity of PSII, content of basic photosynthetic pigments, lipid peroxidation, and accumulation ofinorganic ions in barley plants under the action of cadmium chloridewas studied. It was shown for the first time that the protectiveeffect of phytomelatonin during short-term treatment is manifested ina decrease in the toxic effect of cadmium on the content ofphotosynthetic pigments and the accumulation of cadmium ions in theshoots and roots of barley plants. The protective effect of melatoninis based on its ability to reduce the intensity of oxidative stress bymaintaining the level of carotenoids and increasing the activity ofantioxidant enzymes. The effectiveness of short-term use of melatoninin a number of indicators exceeds its protective effect from long-termexposure. The data obtained indicate the possibility of usingmelatonin as a substance that induces the state of plant priming uponsubsequent exposure to cadmium.

Short-Term Pretreatment with Melatonin Increases the Resistance of Barley Plants to the Subsequent Action of Cadmium

The effect of short-term and long-term root treatment with melatonin on growth parameters, photochemical activity of PSII, content of basic photosynthetic pigments, lipid peroxidation, and accumulation of inorganic ions in barley plants under the action of cadmium chloride was studied. It was shown for the first time that the protective effect of phytomelatonin during short-term treatment is manifested in a decrease in the toxic effect of cadmium on the content of photosynthetic pigments and the accumulation of cadmium ions in the shoots and roots of barley plants. The protective effect of melatonin is based on its ability to reduce the intensity of oxidative stress by maintaining the level of carotenoids and increasing the activity of antioxidant enzymes. The effectiveness of short-term use of melatonin in a number of indicators exceeds its protective effect from long-term exposure. The data obtained indicate the possibility of using melatonin as a substance that induces the state of plant priming upon subsequent exposure to cadmium.

The Effects of Rhizosphere Inoculation with Pseudomonas mandelii on Formation of Apoplast Barriers, HvPIP2 Aquaporins and Hydraulic Conductance of Barley.

Pseudomonas mandelii strain IB-Ki14 has recently been shown to strengthen the apoplastic barriers of salt-stressed plants, which prevents the entry of toxic sodium. It was of interest to find out whether the same effect manifests itself in the absence of salinity and how this affects the hydraulic conductivity of barley plants. Berberine staining confirmed that the bacterial treatment enhanced the deposition of lignin and suberin and formation of Casparian bands in the roots of barley plants. The calculation of hydraulic conductance by relating transpiration to leaf water potential showed that it did not decrease in bacteria-treated plants. We hypothesized that reduced apoplastic conductivity could be compensated by the higher conductivity of the water pathway across the membranes. This assumption was confirmed by the results of the immunolocalization of HvPIP2;5 aquaporins with specific antibodies, showing their increased abundance around the areas of the endodermis and exodermis of bacteria-treated plants. The immunolocalization with antibodies against auxins and abscisic acid revealed elevated levels of these hormones in the roots of plants treated with bacteria. This root accumulation of hormones is likely to be associated with the ability of Pseudomonas mandelii IB-Ki14 to synthesize these hormones. The involvement of abscisic acid in the control of aquaporin abundance and auxins—in the regulation of and formation of apoplast barriers—is discussed.

Secondary Active Transporters Decrease Cytokinin Flow into Barley Shoots and Inhibit their Growth under Phosphate Deficit

Secondary active transport is one of the most important mechanisms controlling cytokinin distribution between shoots and roots which enables the adaptive growth reaction of barley. Concentrations (ng/g of fresh mass) and contents (ng/organ) of different forms of cytokinins were determined in shoots and roots of barley plants by immunoassay. It was shown that under phosphate deficit the maintenance of root growth, inhibition of root branching and decline in shoot mass of barley plants (Hordeum vulgare 'Prairie') was due to decline in shoot cytokinins and their accumulation in the roots. Protonophore carbonyl cyanide-m-chlorophenylhydrazone as an inhibitor of secondary active transport leveled off hormonal reaction to phosphate deficit: it prevented accumulation of cytokinins in roots, increased their content in shoots and changed the percentage of zeatin and its derivatives in total cytokinin content in roots and shoots. A data analysis showed that in roots, protonophore did not change significantly the content of ribosides and nucleotides of zeatin, while uptake of free zeatin by cells was significantly affected by the protonophore and its content decreased dramatically. The role of secondary active trans-membrane transfer is discussed in the context of cytokinins transport from roots to shoots under phosphate deficit

First Report of Meloidogyne graminicola (Nematoda: Meloidogynidae) on Barley (Hordeum vulgare) in Brazil

Winter barley (Hordeum vulgare L.) has become a growing addition to cereal crops in Brazil and, until recently, the root-knot nematode (Meloidogyne sp.) has not been reported to infect barley in this country. Meloidogyne graminicola is a major pathogen of rice (Oryza sativa L.) and causes significant yield losses in both upland and flooded fields in Rio Grande do Sul, Brazil (Negretti et al. 2017). In September 2017, many nematode galls were observed on the roots of barley plants (cv. BRS Brau), and samples were taken from areas in Santa Maria county (29°45′S; 53°38′W), Rio Grande do Sul State, Brazil. Meloidogyne sp. was identified using esterase phenotypes (n = 40), perineal patterns (n = 40), morphological measurements of second-stage juveniles (J2) (n = 50), and amplification and sequencing of the ITS1-5.8S-ITS2 rRNA region and the D2–D3 fragment of the 28S ribosomal RNA gene. The barley root systems were also processed to determine the number of J2s and eggs of Meloidogyne sp. The nematode population density observed in the samples was 2,585 eggs plus J2s per gram of barley root. The J2s had the following morphometric characteristics: length (L) = 458.2 ± 38.0 (390.0 to 476.0) µm, a = 26.6 ± 1.5 (24.9 to 29.4), c = 6.15 ± 0.4 (5.1 to 7.6), stylet = 14.2 ± 0.5 (13.4 to 15.0) µm, dorsal esophageal gland orifice (DGO) = 3.9 ± 0.4 (3.4 to 4.6) µm, tail length = 70.5 ± 4.7 (63.1 to 75.3) µm, and hyaline tail terminus = 19.5 ± 1.8 (14.5 to 25.5) µm. The female’s perineal patterns were oval with a low dorsal arch without a lateral line. The cuticular striations were smooth and thick in the dorsal region of the vulva, and the phasmids were close together (13.1 to 17.9 μm). These morphological characteristics matched the original description of M. graminicola (Golden and Birchfield 1968). The polymorphisms of esterase bands seen using electrophoresis revealed the phenotype VS-1 (Rm = 0.71) typical of M. graminicola. The sequence homologies were determined by comparing them with those from GenBank. PCR amplicons of D2–D3 of the 28S and ITS1-5.8S-ITS2 rRNA regions were 531 bp (GenBank MH707259) and 440 bp (MH703577), respectively. The sequences of both markers exhibited 99 and 100% identity, respectively, with sequences corresponding to M. graminicola isolates (D2–D3: MH843665 and KY660544; ITS: MH842692 and KY346887) from Brazil and China. Identification of the nematode species was confirmed by PCR using the species-specific sequence-characterized amplified region (SCAR) with primer sets GRAJ17-1F and GRAJ17-1R. PCR amplification using SCAR produced a specific fragment of the expected size (∼230 bp) in M. graminicola (Mattos et al. 2019). In greenhouse tests, barley plantlets from cv. BRS Brau that were maintained in pots with sterilized soil were inoculated with 5,000 eggs plus J2s of the original population of M. graminicola using 10 replicates; a noninoculated control was included in the test. After 60 days, the growth of all the inoculated plants was reduced compared with that of the control. Galling symptoms on the roots were similar to those in the field, with a nematode reproduction factor (final population/initial population) of 28.5. There were no galls on the roots of noninoculated plants, and plant development was not affected. The morphological and molecular characteristics of the reisolated root-knot nematode were identical to those of M. graminicola. M. graminicola has been reported on barley in India (Vaish et al. 2012). To our knowledge, this is the first report on M. graminicola parasitizing barley in Brazil. This finding is of great importance for Brazilian barley production because this nematode can severely damage barley plants and become a major problem for the cultivation of this crop.

ВЛИЯНИЕ АБСЦИЗОВОЙ КИСЛОТЫ НА СОДЕРЖАНИЕ АУКСИНОВ И РОСТ БОКОВЫХ КОРНЕЙ У РАСТЕНИЙ ЯЧМЕНЯ

ВЛИЯНИЕ АБСЦИЗОВОЙ КИСЛОТЫ НА СОДЕРЖАНИЕ АУКСИНОВ И РОСТ БОКОВЫХ КОРНЕЙ У РАСТЕНИЙ ЯЧМЕНЯ

Arbuscular mycorrhizal fungi increase grain zinc concentration and modify the expression of root ZIP transporter genes in a modern barley (Hordeum vulgare) cultivar

The positive effects of arbuscular mycorrhizal fungi (AMF) on the zinc (Zn) nutrition of a number of cereal species has been demonstrated, but for Hordeum vulgare (barley), this has been scarcely investigated. Zn is taken up by ZIP transporters in the roots, and several barley ZIP transporter genes are up-regulated under Zn deficient conditions.We grew a modern cultivar of barley (cv. Compass) at five different soil Zn concentrations ranging from no addition through to a toxic concentration. The plants were either inoculated with the AMF Rhizophagus irregularis, or mock-inoculated. At harvest, measurements of biomass, tissue Zn concentration, and expression of ZIP transporter genes were taken.Inoculation of barley with AMF resulted in improved grain and straw Zn concentrations, especially at low soil Zn concentrations, but did not increase the biomass of the plants. Of the five HvZIP genes tested that are up-regulated under low Zn conditions, one gene (HvZIP13) was significantly up-regulated by mycorrhizal colonisation at the lowest Zn treatment. Two other ZIP genes were down-regulated in mycorrhizal plants under low soil Zn.Inoculation with AMF has an effect on ZIP transporter genes in the roots of barley plants. Furthermore, AMF may be more useful for improving quality of barley grain in terms of Zn concentrations, rather than improving yield.

Detection of Polymyxa graminis in a barley crop in Australia

Polymyxa graminis was detected in the roots of barley plants from a field near Wondai, Queensland, in 2009. P. graminis was identified by characteristic sporosori in roots stained with trypan blue. The presence of P. graminis f. sp. tepida (which is hosted by wheat and oats as well as barley) in the roots was confirmed by specific PCR tests based on nuclear ribosomal DNA. P. graminis is the vector of several damaging soil-borne virus diseases of cereals in the genera Furovirus, Bymovirus and Pecluvirus. No virus particles were detected in sap extracts from leaves of stunted barley plants with leaf chlorosis and increased tillering. Further work is required to determine the distribution of P. graminis in Australian grain crops and the potential for establishment and spread of the exotic soil-borne viruses that it vectors.

Mechanism of Potassium Alleviation of Manganese Phytotoxicity in Barley

ABSTRACT Manganese (Mn) toxicity and potassium (K) deficiency are the major factors that limit plant growth and development in acid soils. The objective of this study was to assess the role of high K on the alleviation of Mn toxicity in barley (Hordeum vulgare L. cv. ‘Minorimugi’) grown in a phytotron for 14 d. Modified half-strength Hoagland-Arnon solution (pH 5.5) was used as the medium. The treatments were (1) 0.25 μ M Mn + 3 mM K (control); (2) 25 μ M Mn + 3 mM K (Mn-toxic); and (3) 25 μ M Mn + 30 mM K (K-alleviated). The Mn-toxic plants showed the symptoms of Mn toxicity and mild iron (Fe) deficiency, whereas in the K-alleviated plants such symptoms were absent. The K-alleviated plants had dry weight, chlorophyll content, and Fe concentration similar to that in the control plants, indicating that high K (30 mM) in the growth medium could alleviate Mn toxicity and Mn-induced Fe deficiency. Roots of plants fed separately with 54Mn and 59Fe in the presence of 3.0 and 30 mM K for 4 h were also studied. Results showed that high K could help in avoiding the accumulation of 54Mn, indicating that K plays an antagonistic role on Mn absorption by roots of barley and its subsequent translocation to the shoots. However, the absorption of 59Fe was not influenced by the high K concentration in a short-term experiment (4 h), indicating that high K does not affect short-term Fe absorption by the roots of barley plants. These results suggested that the alleviating effect of high K could be attributed to the antagonistic effect of K on Mn absorption by roots and translocation into shoots.

Influence of Root Oxygen Deficiency on Photosynthesis and Antioxidant Status in Barley Plants1

Roots of barley plants (Hordeum vulgare L., cv. Alfa) were subjected to hypoxia for 120 h. By 72 to 120 h of soil flooding, a noticeable decrease in the rate of CO2 assimilation and transpiration was observed. A drop in the activities of Rubisco and photorespiratory enzymes was found. We examined the changes in the activities of enzymes involved in the antioxidative system and stress markers related to membrane integrity, namely, lipid peroxidation and electrolyte leakage. Catalase and peroxidase activities were increased during the experiment, whereas superoxide dismutase activity drastically decreased.

Molybdenum cofactor biosynthesis in two barley ( Hordeum vulgare L.) genotypes as affected by nitrate in the tissue and in the growth medium

Two barley genotypes, the wild type and the narla, nar7w mutant, impaired in two structural genes of the nitrate reductase (NR) apoproteins, exhibited a considerable level of molybdenum cofactor (MoCo) when grown in the absence of NO 3. Increasing concentrations of nitrate in the nutrient solutions did not affect MoCo content in shoots and roots of barley plants during the first 7 h of incubation. The MoCo and pterin content of the plants remained also unchanged during 24 h induction in 0.1 mM nitrate. Removal of NO 3 − from the nutrient medium caused a rapid loss of NR activity in the shoots of wild type plants while MoCo and pterin content remained unaffected by the presence or absence of nitrate in the medium. Previous observations of MoCo induction in higher plants by NO 3 − by a number of researchers may have been due to an overestimation of the actual MoCo content due to NO 3 − accumulation in the tissue and its reduction by NADPH during the NR complementation process which resulted in nitrite accumulation. Exclusion of NADPH from the complementation medium prevented nitrite formation and allowed to estimate MoCo content in plant tissues containing a wide range of nitrate concentrations. The genotype narla:nar7w, when grown in nitrate, exhibited MoCo levels similar to that of wild type plants.

Studies of the Uptake of Nitrate in Barley

(13)NO(3) (-) was used to investigate patterns of NO(3) (-) influx into roots of barley plants (Hordeum vulgare L. cv Klondike) previously grown with (;induced') or without (;uninduced') a source of external NO(3) (-) ([NO(3) (-)](0)). In both induced and uninduced plants, (13)NO(3) (-) influx was biphasic in the range from 0.005 to 50 moles per cubic meter [NO(3) (-)](0). In the low concentration range (<1 mole per cubic meter for induced plants and <0.3 mole per cubic meter for uninduced plants), influx was saturable and V(max) and K(m) values for influx either increased or decreased according to NO(3) (-) pretreatment. By contrast, (13)NO(3) (-) influx in the high concentration range revealed a strictly linear concentration dependence. These fluxes appeared to be mediated by a constitutive, rather than an inducible, transport system.

Root Excision Decreases Nutrient Absorption and Gas Fluxes

The roots of barley plants (Hordeum vulgare L. cv Steptoe) were monitored before and after excision for net uptake of carbon dioxide, oxygen, ammonium, potassium, nitrate, and chloride and for their content of sucrose, glucose, fructose, and malic acid. All fluxes began to attenuate within 2 hours after excision. Net potassium uptake returned to control levels 6 hours after excision, but carbon dioxide, oxygen, ammonium, and nitrate fluxes continued to diminish for the remainder of the observation period. The addition of 0.1 molar glucose or 0.1 molar sucrose to excision medium had no significant effect on these changes in ion and gas fluxes. Net chloride uptake was negligible for all treatments. Sugar and malic acid content of the root declined after excision. Sucrose and glucose levels remained depressed for the entire observation period, whereas fructose and malic acid returned to control levels after 9 hours. These results indicate that excision has profound, adverse effects on root respiration and the absorption of mineral nitrogen.

Localization of phytosiderophore release and of iron uptake along intact barley roots

Under iron deficiency the release of so‐called phytosiderophores by roots of barley plants (Hordeum vulgare L. cv. Europa) was greater by a factor of 10 to 50 compared to iron‐sufficient plants. This enhanced release occurred particularly in apical zones of the seminal roots and in the lateral root zones. Under iron deficiency, uptake rates for iron, supplied as FeIII phytosiderophore, increased by a factor of ca 5 as compared to iron‐sufficient plants. This enhanced uptake rate for iron was also much more pronounced in apical than in basal root zones. In contrast, with supply of the synthetic iron chelate, FelII EDDHA (ferric diaminoethane‐N, N‐di‐o‐hydroxyphenyl acetic acid), the Fe deficiency‐enhanced uptake rates for iron were only small and similar along the roots, except for the lateral root zones. The high selectivity of barley roots for uptake and translocation of FeIII phytosiderophores compared with FeIII EDDHA is reflected by the fact that, at the same external concentration (2 μM), rates of uptake and translocation of iron from FeIII phytosiderophores were between 100 (Fe‐sufficient) and 1 000 times higher (Fe‐deficient plants) than from FeIII EDDHA. The relatively high rates of uptake and particularly of translocation of iron supplied as FeIII EDDHA in the zone of lateral root formation strongly suggest an apoplastic pathway of radial transport of the synthetic iron chelate into the stele in this root zone.The results demonstrate that apical root zones are the main sites both for Fe deficiency‐enhanced release of phytosiderophores and for uptake and translocation of iron supplied as FeIII phytosiderophores.

A Model for the Regulation of K+ Influx, and Tissue Potassium Concentrations by Negative Feedback Effects upon Plasmalemma Influx

By means of a modified Michaelis-Menten equation for K(+) influx, which includes terms for root and external K(+) concentrations (root [K(+)] and [K(+)](0), respectively) it is possible to predict the manner in which short-term (perturbation) fluxes of K(+) into roots of barley plants (Hordeum vulgare cv Fergus) vary with root [K(+)] and [K(+)](0). Influx values derived from this equation were used to predict changes of root and shoot [K(+)] and K(+) absorption rates (as functions of time and [K(+)](0)) from a knowledge of K(+) efflux, relative growth rates of roots and shoots, and the partitioning of absorbed K(+) between these organs. A microcomputer program was employed to model these changes in low-salt plants following transfer to solutions in which [K(+)](0) was maintained at values ranging from 5 to 1000 millimoles per cubic meter. The model was operated on the basis of 10 minute absorption periods which provided data for continuous ;updating' of tissue [K(+)]. The simulations were undertaken for periods corresponding to 30 days. During this time the model accurately predicted the manner in which K(+) influx and root and shoot [K(+)] gradually approach values which are essentially independent of [K(+)](0). The computer program was also used to predict the outcome of changing various external and internal parameters of the proposed regulatory system. The results of these simulations are discussed in the context of current models for negative feedback control of ion fluxes.

A Lag Phase in Vacuolar Accumulation of Cl- Ions in Roots of Intact Barley Plants

Summary The presence of NO 3 - in the external solution appears to interfere with Cl - uptake by low-salt roots of barley plants during the second (purely vacuolar) period of uptake but not during the first period. The inference is that the interaction is located at the tonoplast. This implies that during the initial period no Cl- ions are accumulated into the vacuoles.

Effects of powdery mildew disease on uptake and metabolism of nitrogen by roots of infected barley

A study was made of the effects of powdery mildew disease on the uptake and metabolism of nitrogen by roots of barley plants grown and infected in solution culture, which provided nitrogen principally in the form of nitrate. Infection decreased nitrate uptake thereby lowering the nitrate content of roots, and of other tissues of the plant. Assimilation of nitrogen through nitrate and nitrite reductases was not affected by infection. The ammonium content of roots, and of infected leaves, increased as a result of infection. Ammonium accumulation resulted from a decrease in the rate of its assimilation, through either glutamate dehydrogenase, or glutamine synthetase and glutamate synthase pathways, as well as enhanced degradation of glutamic acid and asparagine. In infected plants, levels of glutamine were lowered by infection, but asparagine accumulated; the activity of asparagine synthetase and β-cyanoalanine synthase increased, which probably helped the plant to detoxify the accumulating ammonium. Changes in nitrogen uptake and metabolism by roots may be initiated by a lack of photoassimilates received by the roots from infected leaves. The significance of the observed changes for the long term survival of the plant is discussed.

The effect of differential root and shoot temperature on the nitrate reductase activity, assayed in vivo and in vitro in roots ofHordeum vulgare (barley)

There was a large increase in nitrate reductase activity (NAR) assayed both in vivo and in vitro in roots of barley plants (cv. Midas_ grown with roots at 10°C and shoots at 20°C, compared with whole plants grown at 20°C. There were diurnal fluctuations in NRA in roots from both treatments, but they were much greater in roots grown at 20°C, where NRA fell to a very low value in the dark period. The diurnal fluctuations in the malate content of the roots were also related to the root growth temperature. Plants with roots grown at the lower temperature had a higher malate content, especially in the dark period where it was 20 times greater than in plants with roots at 20°C. At all times there was a three-fold increase in soluble carbohydrate in cooled roots and diurnal fluctuations were much less pronounced than those of malate. Growth at low temperatures increased the total flux of amino N into the xylem sap and increased the proportion of reduced N in the total N flux. At certain times of day both 10°C- and 20°C-grown roots responded to exogeneous malate by increasing the flux of amino acid into the xylem sap, although this effect was always more pronounced in 20°C-grown roots.

The effect of differential root and shoot temperature on the nitrate reductase activity, assayed in vivo and in vitro in roots ofHordeum vulgare (barley)

There was a large increase in nitrate reductase activity (NAR) assayed both in vivo and in vitro in roots of barley plants (cv. Midas_ grown with roots at 10°C and shoots at 20°C, compared with whole plants grown at 20°C. There were diurnal fluctuations in NRA in roots from both treatments, but they were much greater in roots grown at 20°C, where NRA fell to a very low value in the dark period. The diurnal fluctuations in the malate content of the roots were also related to the root growth temperature. Plants with roots grown at the lower temperature had a higher malate content, especially in the dark period where it was 20 times greater than in plants with roots at 20°C. At all times there was a three-fold increase in soluble carbohydrate in cooled roots and diurnal fluctuations were much less pronounced than those of malate. Growth at low temperatures increased the total flux of amino N into the xylem sap and increased the proportion of reduced N in the total N flux. At certain times of day both 10°C- and 20°C-grown roots responded to exogeneous malate by increasing the flux of amino acid into the xylem sap, although this effect was always more pronounced in 20°C-grown roots.

New evidence for the metabolic conversion of aspartate-4-&lt;sup&gt;14&lt;/sup&gt;C to glutamine-l-&lt;sup&gt;14&lt;/sup&gt;C during the initial period of ammonia assimilation in the roots of barley plants

New evidence for the metabolic conversion of aspartate-4-&lt;sup&gt;14&lt;/sup&gt;C to glutamine-l-&lt;sup&gt;14&lt;/sup&gt;C during the initial period of ammonia assimilation in the roots of barley plants