Growth Of Barley Seedlings Research Articles

Silicon regulates phosphate deficiency through involvement of auxin and nitric oxide in barley roots.

Silicon application mitigates phosphate deficiency in barley through an interplay with auxin and nitric oxide, enhancing growth, photosynthesis, and redox balance, highlighting the potential of silicon as a fertilizer for overcoming nutritional stresses. Silicon (Si) is reported to attenuate nutritional stresses in plants, but studies on the effect of Si application to plants grown under phosphate (Pi) deficiency are still very scarce, especially in barley. Therefore, the present work was undertaken to investigate the potential role of Si in mitigating the adverse impacts of Pi deficiency in barleyHordeum vulgareL. (var. BH902). Further, the involvement of two key regulatory signaling molecules--auxin and nitric oxide (NO)--in Si-induced tolerance against Pi deficiency in barley was tested. Morphological attributes, photosynthetic parameters, oxidative stress markers (O2·-, H2O2, and MDA), antioxidant system (enzymatic--APX, CAT, SOD, GR, DHAR, MDHAR as well as non-enzymatic--AsA and GSH), NO content, and proline metabolism were the key traits that were assessed under different treatments. The P deficiency distinctly declined growth of barley seedlings, which was due to enhancement in oxidative stress leading to inhibition of photosynthesis. These results were also in parallel with an enhancement in antioxidant activity, particularly SOD and CAT, and endogenous proline level and its biosynthetic enzyme (P5CS). The addition of Si exhibited beneficial effects on barley plants grown in Pi-deficient medium as reflected in increased growth, photosynthetic activity, and redox balance through the regulation of antioxidant machinery particularly ascorbate-glutathione cycle. We noticed that auxin and NO were also found to be independently participating in Si-mediated improvement of growth and other parameters in barley roots under Pi deficiency. Data of gene expression analysis for PHOSPHATE TRANSPORTER1 (HvPHT1) indicate that Si helps in increasing Pi uptake as per the need of Pi-deficient barley seedlings, and also auxin and NO both appear to help Si in accomplishing this task probably by inducing lateral root formation. These results are suggestive of possible application of Si as a fertilizer to correct the negative effects of nutritional stresses in plants. Further research at genetic level to understand Si-induced mechanisms for mitigating Pi deficiency can be helpful in the development of new varieties with improved tolerance against Pi deficiency, especially for cultivation in areas with Pi-deficient soils.

Effect of Abiotic Stresses from Drought, Temperature, and Density on Germination and Seedling Growth of Barley (Hordeum vulgare L.).

Seed germination and seedling growth are highly sensitive to deficit moisture and temperature stress. This study was designed to investigate barley (Hordeum vulgare L.) seeds' germination and seedling growth under conditions of abiotic stresses. Constant temperature levels of 5, 10, 15, 20, 25, 30, and 35 °C were used for the germination test. Drought and waterlogging stresses using 30 different water levels were examined using two methods: either based at 1 milliliter intervals or, on the other hand, as percentages of thousand kernel weight (TKW). Seedling density in a petri dish and antifungal application techniques were also investigated. Temperature significantly impacted germination time and seedling development with an ideal range of 15-20 °C, with a more comprehensive range to 10 °C. Higher temperatures reversely affected germination percentage, and the lower ones affected the germination and seedling growth rate. Germination commenced at 130% water of the TKW, and the ideal water range for seedling development was greater and more extensive than the range for germination, which means there is a difference between the starting point for germination and the seedling development. Seed size define germination water requirements and provides an objective and more precise basis suggesting an optimal range supply of 720% and 1080% of TKW for barley seedling development. A total of 10 seeds per 9 cm petri dish may be preferable over greater densities. The techniques of priming seeds with an antifungal solution (Bordóilé or Hypo) or antifungal application at even 5 ppm in the media significantly prevented fungal growth. This study is novel regarding the levels and types of abiotic stresses, the crop, the experimental and measurement techniques, and in comparison to the previous studies.

Influence of chitosan and hydroxycinnamic acids conjugates and nanoparticles on the growth of barley seedlings and proline contents under saline stress

The effect of seed treatment with various materials of chitosan and hydroxycinnamic acids on the growth of barley seedlings was evaluated. It was shown that chitosan-hydroxycinnamic acid conjugates and nanoparticles had no negative effect on the initial stages of the growth of barley seedlings. Adaptation of seedlings after 24 h exposure to 4 % NaCl in the samples of conjugates of 30 kDa chitosan with caffeic and ferulic acids was more effective. There was a decrease in proline contents and restoration of the growth activity under post-stress conditions.

Pollution Characteristics and Phytotoxicity of Heavy Metals in the Soil Around Coal Gangue Accumulation Area

Coal gangue releases heavy metals and other pollutants through weathering and rain conditions during the natural accumulation process, which causes serious ecological risks to the surrounding soil environment. This study aimed to analyze the content of heavy metals in the soil around a coal gangue dump and to explore the phytotoxic effects induced by the exposure of soil samples to comprehensively assess the ecological risks of the soil around the coal gangue accumulation area. The results showed that the average contents of Cd, Pb, and Zn in the soil around the coal gangue accumulation area exceeded the background values of soil elements in Shanxi Province, and the content of heavy metals in the soil first increased and then decreased with the distance from the coal gangue dump. The enrichment factor results also showed that the pollution of Cd, Pb, and Zn in the soil was serious. The growth of barley seedlings was inhibited after exposure to the soil at different distances from the gangue dump, and some soils could induce the decrease in chlorophyll and the increase in MDA content; the increase in SOD, POD, and GSH activities; the significant decrease in CAT activities; and the decrease in mitotic index (MI) and significant increase in micronucleus rate (MN) in root tip cells. The Pearson correlation coefficient showed that Cr, As, and Zn were significantly positively correlated with the shoot weight, root weight, and micronucleus rate of barley, whereas Cu and Pb were significantly negatively correlated with the chlorophyll and micronucleus rate, respectively.

Effect of γ-aminobutyric Acid on Phenolics Metabolism in Barley Seedlings under Low NaCl Treatment.

It has been revealed that high NaCl stress (>60 mmol L−1) induced phenolics accumulation in barley seedlings, with γ-aminobutyric acid (GABA) playing a key role. Interestingly, low NaCl stimulus (20 mmol L−1) enhancing phenolics synthesis and growth of barley seedlings was also reported recently. Hence, exogenous GABA and its bio-synthesis inhibitor 3-mercaptopropionic acid (3-MP) were applied to reveal the mechanism of GABA regulating phenolics metabolism in barley seedlings treated with 20 mmol L−1 NaCl. The contents of total phenolics and flavonoids significantly increased by 11.64% and 14.52% under NaCl, respectively. The addition of GABA further increased phenolics and flavonoids contents, especially for gallic acid, protocatechuic acid, caffeic acid, and quercetin, compared with NaCl treatment. Simultaneously, GABA increased the activities and mRNA levels of phenylalanine ammonia lyase (PAL), cinnamic acid 4-hydroxylase (C4H), and 4-coumalyl CoA ligase (4CL). The addition of 3-MP suppressed the above effects, except for increasing the protein levels of PAL, C4H, and 4CL. Low concentration of NaCl not only promoted growth, but also stimulated endogenous GABA metabolism to affect key enzymes activities and mRNA levels for phenolics synthesis in barley seedlings.

Phenotype, Physiology, and Gene Expression of Barley Seedlings in Response to Nano Zinc Oxide Stress

In recent years, zinc oxide nanoparticles (ZnO NPs) have been widely used as zinc fertilizers and pesticides. The use of ZnO NPs in this way can provide benefits to humans, but also has potential risks. ZnO NPs inevitably enter the environment during their production and use, which affects the ecological environment and crop growth. In order to investigate the phenotype, physiology, and gene expression of barley (Hordeum vulgare L.) seedlings under ZnO NPs stress, the barely cultivars ZJU3 (P21), Golden Promise (GP) and L23 were chosen for study. Different ZnO NPs concentrations were applied to compare the physiological and biochemical indexes of the barley seedlings and the responses of six stress-related genes, when seedlings were cultured to the two-leaf stage through hydroponics. The results showed that the density of brown spots on the leaf surface increased with increasing ZnO NPs concentration. ZnO NPs stress inhibited the root growth of barley seedlings, and P21 was the most sensitive. Furthermore, ZnO NPs stress could stimulate plants to produce a large number of reactive oxygen species (ROS), resulting in an imbalance between the production and removal of ROS and membrane lipid peroxidation in plants. This imbalance inhibited the growth and development of the barley seedlings. With increasing ZnO NPs concentration, the activity of superoxide dismutase was gradually increased, the activity of catalase was progressively decreased, and the contents of malondialdehyde and proline were increased. Compared with the control, among six stress-related genes, the expression levels of five genes were downregulated and one gene was upregulated in the experimental group. This study preliminarily revealed the toxic effect of ZnO NPs on seedlings and the effect on the expression of stress-related resistance genes in different barley varieties.

Screening of Worldwide Barley Collection for Drought Tolerance: The Assessment of Various Physiological Measures as the Selection Criteria.

Drought is a devastating environmental constraint affecting the agronomic production of barley. To facilitate the breeding process, abundant germplasm resources and reliable evaluation systems to identify the true drought-tolerant barley genotypes are needed. In this study, 237 cultivated and 190 wild barley genotypes, originating from 28 countries, were screened for drought tolerance under the conditions of both water deficit and polyethylene glycol (PEG)-simulated drought at seedling stage. Drought stress significantly reduced the plant growth of all barley genotypes, but no significant difference in drought-induced reduction in the performance of barley seedlings was observed under these two drought conditions. Both cultivated and wild barley subspecies displayed considerable genotypic variability in drought tolerance, which underpinned the identification of 18 genotypes contrasting in drought tolerance. A comparative analysis of drought effects on biomass, water relation, photosynthesis, and osmotic adjustment was undertaken using these contrasting barley genotypes, in order to verify the reliability of the screening and to obtain the credible traits as screening criteria of drought tolerance in barley. As expected, the selected drought-tolerant genotypes showed much less reduction in shoot biomass than drought-sensitive ones under water deficit, which was significantly positively correlated with the results of large-scale screening, confirming the reliability of the screening for drought tolerance under two drought conditions in this study. Likewise, the traits of water relation, photosynthetic activity, and osmotic adjustment differed greatly between the contrasting genotypes under water deficit stress, and they were highly correlated to the growth of barley seedlings, suggesting the potential of them to be the selection criteria for drought tolerance. The analysis of the variable importance of these traits in drought tolerance indicated that sap osmolality and relative water content in the youngest fully-expanded leaf are the suitable selection criteria of screening for drought tolerance in barley at seedling stage.

Evaluation of physiological and biochemical aberration linked to effect of sodium dodecyl sulphate on barley seedlings

Sodium dodecyl sulphate (SDS) amount in domestic and industrial effluents is consistently increasing since SDS is available in almost all cleaning products. Therefore, it has become one of the potential destructive factors on habitats such as agricultural areas and aquatic environments. This study was carried out to evaluate the SDS-induced changes on barley (Hordeum vulgare L. cv. Olgun) seedlings. Barley seedlings were hydroponically cultivated for nine days at optimal conditions and, then, exposed to five different doses of SDS. After 72 h from SDS addition, root and coleoptile lengths were seriously reduced as compared to control. Also, SDS decreased soluble protein, chlorophyll a, chlorophyll b and carotenoid contents of the barley leaves. Furthermore, the SDS-induced reductive effects on protein profiles of barley leaves were also detected with electrophoresis. SDS caused serious decreases in activities of antioxidant enzymes, including superoxide dismutase, catalase, and ascorbate peroxidase and glutathione reductase except for peroxidase. Moreover, the SDS led to the emergence of oxidative damage symptoms that were manifested by the increased superoxide anion formation, hydrogen peroxide content and lipid peroxidation level of barley seedlings. Eventually, the results of the present study revealed that SDS cause to a severe reduction in the growth of barley seedlings.

Specificity of Cd, Cu, and Fe effects on barley growth, metal contents in leaves and chloroplasts, and activities of photosystem I and photosystem II

Cd, Cu, and Fe were used to reveal the specificity of their toxic actions. We studied the effects of heavy metals on the growth of barley seedlings, contents of cations in leaves and chloroplasts, induced chlorophyll fluorescence and P700 light absorption. Differences were found at each level of research. We measured the contents of Cd, Cu, Fe, Mn, Zn, Ca, Mg, and K. The proportion of cations in leaves targeted to chloroplasts varied from 0.1% (K) to >90% (Fe). Their levels changed in different ways. We found no correlation between changes in cation contents in leaves and chloroplasts. Treatment with Cd, Cu, and Fe increased the contents of some cations. The extra portions were targeted primarily out of chloroplasts, which was most noticeable in the case of Cu and Fe. Cd treatment decreased non-photochemical quenching with concomitant increases in closed photosystem II. We introduced new coefficients qC for closed photosystem II and X(II) to compare the yields of photosystem II and photosystem I. Cd likely decreased both PSI content in leaves and its quantum yield. In control plants, the quantum yield ratio of PSI/PSII increased gradually from 1.25 under low light to 4 under high light. Cd treatment prevented the increase under moderate light; under high light the ratio reached 2. Cu treatment increased the acceptor side limitation of photosystem I under low light; components of the Calvin cycle likely demand more light for activation in Cu-treated plants.

Seed Germination and Early Seedling Growth of Barley at Negative Water Potentials

The impacts of climate change may increase the duration and frequency of droughts, which would have deleterious effects on crop establishment. The objectives of this study were to determine the effects of moisture stress on seed germination and seedling growth of six winter barley (Hordeum vulgare) lines and discuss how the data are used to select plant materials for rapid germination. Twenty-five seeds of each line were germinated in water of potentials of −2.0, −1.6, −1.2, −0.8, −0.4, and 0 MPa for 4- and 7-days. The experimental design was a factorial arrangement of treatments (barley lines and water potential treatments) in a randomized block replicated four times and repeated twice. The 4- and 7-day percentage seed germination varied with line (p < 0.01), water potential treatment (p < 0.01), and line × treatment interactions (p < 0.01). The seed germination rate varied with water potential treatment (p < 0.01), and line × treatment interactions (p < 0.01). The data indicated that enough variation was present to effectively select and breed cultivars for improved germination at a negative water potential. Studying seed germination under moisture stress is the first step for developing an effected selection pressure for identifying plant materials with rapid seed germination.

Effects of chlorine dioxide on the germination, oxidative metabolism and growth of barley seedlings (Hordeum vulgare L.)

The effects of chlorine dioxide, ClO2, on the germination, oxidative metabolism and growth of barley seedlings were investigated. Barley seeds were separately treated with 0, 500, 1000 and 2000 mg.L−1 ClO2 solutions. Differences in the percentage of seed germination were observed in treatments with 1000 and 2000 mg.L−1 ClO2 solutions only. However, 1000 and 2000 mg.L−1 ClO2 significantly decreased the germination percentage. No significant difference in the MDA content, electrolyte leakage and amount of chlorophyll was observed in seedlings germinated from seeds treated with 0, 500 and 1000 mg.L−1 of ClO2. Similarly, POD and CAT activities showed no significant differences in seedlings germinated from seeds treated with 0 and 500 mg.L−1 while with 1000 mg.L−1 ClO2 there was an increase of these activities. Although there was no significant difference in the above ground part fresh weight between barley seedlings in which seeds were treated with distilled water and ClO2, the fresh weight of barley roots in which seeds were treated with ClO2 was significantly higher than that of control. The total length of barley roots and the number of roots were also increased. The lignin content of barley roots was markly reduced. Staining with Evans blue indicated that barley roots were not obviously damaged. Furtherly, the stimulation of the cell membrane H+-ATPase activity and root activity were observed to be induced by ClO2.

Roles of Seed Components in the Growth of Barley Seedlings under Salt Stress

The cereal endosperm provides nutrients for seedling growth. The effects of seed components in seedling establishments under salt stress are, however, not yet fully explored. In this study, 60 barley recombinant inbred lines derived from Lewis × Karl cross were grown in four different environments, and the seed contents of starch, total soluble protein, phytate, total phenolics, total flavonoids and total inorganic phosphorus were determined in the harvested grains. Seeds of each line from the four environments were also assayed for seedling growth under saline treatments from 0 to 400 mM NaCl. Root and shoot lengths after 7 days decreased with increasing salt concentration. Correlations between seed components and either root or shoot length were established across the four seed sources. ANOVA showed a significant environment/source effect for both seed components and seedling growth, although the latter was less affected by the seed-production environment. Modeling seedling length across multiple salinities for each seed source showed that the environment with the most saline-tolerant root-growth curve was that associated the highest seed phosphorus content. Correlations between seed components and seedling growth traits highlighted phytate and total inorganic phosphorus as key components for seedling growth under moderate salinities. Seed phytate contents benefited seedling growth, even at high salinities, suggesting an additional role for this seed component under stressful growth conditions, possibly linked to its potential function as an osmolyte source.

Differential influence of molybdenum and tungsten on the growth of barley seedlings and the activity of aldehyde oxidase under salinity

The influence of molybdenum, tungsten on germination and growth of barley Hordeum vulgare L. was studied. Results of this study revealed the differential effect of heavy metals on seedlings growth. Exogenous molybdenum treatment stimulated the growth of seedlings. The addition of the metal significantly stimulated root elongation. Contrastingly, the addition of tungsten resulted in increased seed germination and inhibits the growth of seedlings. The negative effect of tungsten on the growth of barley was more profound for roots of plants. In addition, the influence of metals on the growth of plants was also tested in saline conditions. It is shown that under salinity stress plant growth drastically decreased in presence of tungsten. Results of this study showed that activity of molybdenum-containing aldehyde oxidase (AO; EC 1.2.3.1) was also significantly affected by metals. The activity of AO in leaves and roots enhanced with increasing concentrations of molybdate, while tungstate treatment inhibited the enzyme activity. Perhaps, the differential influence of molybdenum and tungsten on the growth of barley is a direct effect of metals on aldehyde oxidase activity in plants. Moreover, the intense negative effect of tungsten treatment on barley growth under salinity conditions emphasizes an important role of aldehyde oxidase in plant resistance to stress factors.

Growth stimulation of barley and biocontrol effect on plant pathogenic fungi by a Cellulosimicrobium sp. strain isolated from salt-affected rhizosphere soil in northwestern Algeria

The plant growth promoting effect of bacterial isolates from salt-affected agricultural rhizospheric soil from Bejaia, Algeria, on barley seedlings as well as biological control abilities of these isolates against phytopathogenic fungi were determined. Four isolates stimulated significantly germination and growth of barley seedlings in an axenic test system and in soil pots. Isolate S16 (Cellulosimicrobium sp.) stimulated the growth of barley seedlings by 185% (stem height of 13.0 ± 0.11 cm) over non-inoculated control seedlings (7.0 ± 0.12 cm). Cellulosimicrobium sp. S16 was found also superior in mycelial growth inhibition assays against the plant pathogenic fungi Botrytis cinerea, Fusarium oxysporum and Verticillium dahliae. Furthermore, several plant growth promoting traits (production of indole acetic acid, inorganic phosphate solubilization, siderophore production) and production of enzymes beneficial for soil fertility (protease, chitinase, amylase and urease) were identified. However, no evidence for nitrogen fixation was found by testing acetylene reduction and the presence of nif-genes. Based on comparative sequence analysis of almost full length 16S-rRNA coding gene fragments, Cellulosimicrobium sp. S16 exhibits the highest similarity of 99.7% to Cellulosimicrobium cellulans (accession number AY665978). Cellulosimicrobium sp. S16 could be a successful candidate for the application as a plant growth promoting inoculant.

Evaluation of roundup-induced toxicity on genetic material and on length growth of barley seedlings

The study was performed in order to evaluate Roundup-induced genotoxic effects in Hordeum vulgare L. cv. Madalin root meristems and to analyze herbicide impact on length growth of barley seedlings. Caryopses were treated for 3 hours and 6 hours with 0.1%, 0.5%, 1.0% and 2.0% Roundup solutions (v/v), containing 0.36 mg ml-1, 1.8 mg ml-1, 3.6 mg ml-1 and 7.2 mg ml-1 glyphosate active ingredient. Mitotic index decreased in both exposure times with concentration increase. In 3-h treatment, its average values decreased from 4.73 ± 0.31% to 1.51 ± 0.43%, whereas in 6-h treatment this parameter declined from 3.86 ± 0.92% to 0.62 ± 0.15%. The highest ana-telophase aberration rates were noted in 3-h treatments (8.91%, 9.19%, 9.47%, 11.25%, comparatively to control - 5.99%). Roundup enhanced the number of metaphase disturbances proving its noxious effect on normal functioning of mitotic spindle. Seedling growth was negatively influenced at all tested concentrations in both exposure times. The length decreased as concentration increased, so that the average length is 7.5-9 times smaller than in control at the maximum concentration, in both exposures.

QUALITATIVE ASSESSMENT OF CADMIUM STRESS USING GENOME TEMPLATE STABILITY IN Hordeum vulgare

Cadmium, a non essential heavy metal, does not play any metabolic role and is considered as toxic element even at very low concentration. It is mainly generated through anthropogenic activities, such as mining deposits, aerial fallout from smelters and from industrial, agricultural, energy and municipal sources (McGrath et al., 2001; McBride, 2003; Entezari et al., 2006). Cadmium (Cd) contamination has become a severe global issue and is considered a dangerous environmental pollutant not only for its neurotoxic, mutagenic and carcinogenic effects, but also for the high water solubility and thereby easier entry into human body via food (Koizumi and Yamada, 2003). Phytotoxicity of heavy metals such as Cd, Cu and Zn is long known and well documented (Prasad, 2004; Panda and Choudhury, 2005). Metal ions may directly interfere with the metabolic activities by altering the conformation of proteins, for example enzymes, transporters or regular proteins, owing to their strong affinities as ligands to sulfhydryl and carboxylic groups (Sharma et al., 2004). Genotoxicity of Cd is directly related to its effect on structure and function of DNA, which may be determined using a number of laboratory methods (Angelis et al., 2000; Unyayar et al., 2006). However, there have been few direct experimental demonstrations of the wider relationships between DNA effects and their subsequent consequences at higher levels of biological organization. To address this issue, it is necessary to develop reliable and reproducible genotoxicity assays that can then be used in conjunction with traditional assays for detecting any impairment of population parameters (e.g. growth, reproduction and viability of offspring). Recently, advances in molecular biology have led to the development of new tools for detection of genetic alteration in response to toxic chemicals tolerance at the level of DNA sequence and structure. DNA based techniques (RFLP, QTL, RAPD, AFLP, SSR and VNTR) are used to evaluate the variation at the DNA sequence level (Cenkci et al., 2009). Random amplified polymorphic DNA (RAPD), developed by Williams et al. (1990) and Welsh and McClelland (1990), is a PCR-based technique that amplifies random DNA fragments of genomic DNA with single short primers of arbitrary nucleotide sequence under low annealing conditions. This technique is used extensively for species classification, genetic mapping and phylogeny etc. in addition, their use in surveying genomic DNA for evidence of various types of DNA damage and mutational events (e.g., rearrangements, point mutation, small insert or deletions of DNA changes) in cells of bacteria, plants and animals (Atienzar et al., 2000; Cenkci et al., 2010; Cambier et al., 2010). It is suggested that alterations in RAPD profiles due to genotoxic exposure can be regarded as changes in genomic template stability (GTS, a qualitative measure of genotoxic effects) (Atienzar et al., 1999). It is known that, heavy metal hyperaccumulation potential of some plant species is very high (Ozturk et al., 2010). This feature makes hyperaccumulators highly suitable for phytoremediation, for clean-up of soil and water. On the other hand, an excess of toxic heavy metal ions induces several cellular stress responses and damage to different cellular components such as membranes, proteins and DNA (Patra et al., 1998; Waisberg et al., 2003; Jimi et al., 2004). Therefore, several plant species, such as Allium cepa, Hordeum vulgare, Arabiodopsis thaliana, Vicia faba and Zea mays. etc., have been used as good bioindicators of genetic toxicity of environmental pollutants in recent years. There are many studies on heavy metal uptake and accumulation by crop plants (Chlopecka, 1996; Otabbong et al., 1997; Ali et al., 2004; Al-Qurainy, 2009). On the other hand, tolerant food crops may be dangerous as carriers of toxic metals in the food chain leading to food toxicity. Barley (Hordeum vulgare) has been identified as a plant for efficient uptake and accumulation of Cd with a phytoremediation potential equal to that of mustard plants (Ebbs and Kochain, 1998; Sridhar et al., 2007). To be efficient metal accumulator, plants require efficient detoxification and tolerance mechanisms at both the cellular and plant level. Hence it is important to study how the different plant and cellular characteristics are affected when Cd are accumulated in barley plants. The aims of this study were to investigate the DNA changes induced by Cd using RAPD technique, and to compare changes in RAPD profiles with growth parameters such as root and shoot growth of barley seedlings in order to improve the knowledge about the capacity of Graminae species as phytoextractors. Hordeum vulgare was chosen as test species because of its worldwide economic importance and extensive cultivation.

Physiological changes in barley plants under combined toxicity of aluminum, copper and cadmium

Crop production on acid soil is markedly reduced, further, a multiple heavy metal pollution except Al on acid soil is detected in many areas. The present study was undertaken to assess the toxicities of Al, Cd, and Cu separately and in combinations, three heavy metals very often coexisting on acid soil, and to identify their interactions in two kinds of barley seedlings differing in Al tolerance. The plant growth, metals accumulations, total soluble protein and sugar contents, MDA contents and the activities of SOD and POD were estimated in roots and leaves after 5-week supply of the heavy metals excess in the nutrient solution. The results indicated that the stress treatments including low pH (pH 4.5) alone all adversely affected plant growth and disturbed the cell metabolism seriously. The development of toxic symptoms corresponded to a high accumulation of Al, Cd, Cu and to a poor increase in soluble sugar contents but to a high increase in MDA contents, to the decrease in soluble protein contents and to the much elevated SOD and POD activities in both roots and leaves. In addition, binary metal combinations of Al + Cd and Al + Cu both produced the synergistic response for the growth of barley seedlings, in particular for Shang 70-119, while, ternary metal combination of Al + Cu + Cd produced different interactions in two kinds of genotypes, thus, the significant synergistic response was seen in Shang 70-119, but the antagonistic response was detected in Gebeina. The different responses to ternary metal combination of two genotypes may result from the different metal bioaccumulation patterns, hence, the existence of Cd and Cu promoted Al accumulation in Shang 70-119 but inhibited Al accumulation in Gebeina.

Effect of plant growth-promoting bacteria and soil compaction on barley seedling growth, nutrient uptake, soil properties and rhizosphere microflora

Inoculants are of great importance in sustainable and/or organic agriculture. In the present study, plant growth of barley (Hordeum vulgare) has been studied in sterile soil inoculated with four plant growth-promoting bacteria and mineral fertilizers at three different soil bulk densities and in three harvests of plants. Three bacterial species were isolated from the rhizosphere of barley and wheat. These bacteria fixed N2, dissolved P and significantly increased growth of barley seedlings. Available phosphate in soil was significantly increased by seed inoculation of Bacillus M-13 and Bacillus RC01. Total culturable bacteria, fungi and P-solubilizing bacteria count increased with time. Data suggest that seed inoculation of barley with Bacillus RC01, Bacillus RC02, Bacillus RC03 and Bacillus M-13 increased root weight by 16.7, 12.5, 8.9 and 12.5% as compared to the control (without bacteria inoculation and mineral fertilizers) and shoot weight by 34.7, 34.7, 28.6 and 32.7%, respectively. Bacterial inoculation gave increases of 20.3–25.7% over the control as compared with 18.9 and 35.1% total biomass weight increases by P and NP application. The concentration of N and P in soil was decreased by increasing soil compaction. In contrast to macronutrients, the concentration of Fe, Cu and Mn was lower in plants grown in the loosest soil. Soil compaction induced a limitation in root and shoot growth that was reflected by a decrease in the microbial population and activity. Our results show that bacterial population was stimulated by the decrease in soil bulk density. The results suggest that the N2-fixing and P-solubilizing bacterial strains tested have a potential on plant growth activity of barley.

Effect of germination temperature on characteristics of phytase production from barley

The effects of germination temperature on the growth of barley seedlings for phytase production were studied at 15, 20 and 25 °C for 6–10 days. The growth rate of the barley seedlings was increased as the germination temperature was increased. The initial rate of total protein production was closely coupled to that of the barley growth, and the rate of total protein production tended to increase as the germination temperature was increased. SDS–PAGE analysis of total protein from the barley seedlings showed time-dependent appearance and disappearance of protein bands. Although no significant phytase activity was detected at zero time of germination, a significant increase in phytase activity up to 7.9-fold occurred during the first several days of germination then decreased. Phosphate production (viz. phytate degradation) in the barley seedlings occurred rapidly at the beginning of germination. However, the rate of production continued to decrease with further germination. A time lag of about 1–2 days between the rate of total protein production and that of phytase production was observed. Unlike the extent of total protein production, that of phytase production was similar irrespective of germination temperature. Partial purification of a crude enzyme extract by hydrophobic interaction chromatography resulted in two phytase fractions (PI and PII). Zymogram analysis demonstrated that PI had two bands with molecular masses of about 66 and 123 kDa while PII had one band corresponding to a molecular mass of about 96 kDa. The optimal temperature for PI was found to be 55 °C, while it was 50 °C for PII. The enzyme fraction PI had a pH optimum at 6.0, whereas the optimum pH for PII was found to be 5.0. Addition of 0.1% (v/v) Tween 80 was found to increase enzyme activity significantly (i.e., 167% for PI and 137% for PII). Phytate in cereals including barley, rice, corn and soybean degraded effectively by the treatment of the barley phytases.

Effect of Salt Stress and Manganese Supply on Growth of Barley Seedlings

Effect of supplemental manganese (Mn) on the growth of salt-stressed barley (Hordeum vulgare L.) was assessed to determine if a salinity-induced Mn deficiency was limiting plant growth. Sodium chloride (NaCl) was added to the black-cotton soil and salinity was maintained at 0.3, 4, 8, 12, and 16 dS m−1. A negative relationship between percent seed germination and increasing salt concentration was obtained, however, results suggested that barley is salt tolerant at seed germination stage. Increasing concentration of NaCl significantly reduced plant growth. Also, salinity induced a Mn deficiency in shoots of plants. Manganese was added to the soil at control and at 8 dS m−1 salinity. Supplemental Mn improved the growth of salt-stressed plants to a limited extent, but it did not improve the growth of control plants. Further, supplemental Mn increased the relative growth rate of salt-stressed plants and this increase was attributed to an increase in the net assimilation rate of salt-stressed plants and not to leaf area ratio. Salt concentration adversely affected the uptake of nitrogen and phosphorus by plants, which resulted in imbalance of nutrients in salt-stressed plants. It appears that factors other than Mn, such as ionic, water- and nutrient-stresses can limit the growth of salt-stressed plants and supplemental Mn has only a limited role in mitigation of adverse effect of salinity.