Root Growth Of Wheat Seedlings Research Articles

Carbohydrate-Derived Superhydrophilic Carbon Aerogels and Their Effects on Seedling Growth of Triticum aestivum.

Synthesis methods of carbon nanomaterials have been developed vigorously in recent years, among which a simple, green, and mature approach is of more research significance. Carbon nanomaterials have depicted an impact on the growth and development of plants. In this study, a new type of carbon nanomaterial, superhydrophilic carbon aerogel (CA), was synthesized via a hydrothermal process using carbohydrates and water-soluble polymers as raw materials. Characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, powder X-ray diffraction, and N2 adsorption analysis, the exemplified CA presented to have porous three-dimensional network structure composed of individual particles with diameters of 25 nm, with reactive surface, single composition, high specific surface area (89.94 m2·g-1), and wide range of density variation. The 9 mg·mL-1 CA suspension had a significant positive effect on the root growth of wheat seedlings, with promoted root elongation (about 67.17% longer) and root diameter (about 28.95% thicker) compared with those of the control group. The cytological results suggested that CA treatment triggered the propagation of meristematic cells, and the increased number of meristematic cells (65.79% more than the control group) led to enhanced root growth by upregulated expression of related phytohormone genes in wheat seedlings.

Humic acid improves wheat growth by modulating auxin and cytokinin biosynthesis pathways.

Humic acids have been widely used for centuries to enhance plant growth and productivity. The beneficial effects of humic acids have been attributed to different functional groups and phytohormone-like compounds enclosed in macrostructure. However, the mechanisms underlying the plant growth-promoting effects of humic acids are only partially understood. We hypothesize that the bio-stimulatory effect of humic acids is mainly due to the modulation of innate pathways of auxin and cytokinin biosynthesis in treated plants. A physiological investigation along with molecular characterization was carried out to understand the mechanism of bio-stimulatory effects of humic acid. A gene expression analysis was performed for the genes involved in auxin and cytokinin biosynthesis pathways in wheat seedlings. Furthermore, Arabidopsis thaliana transgenic lines generated by fusing the auxin-responsive DR5 and cytokinin-responsive ARR5 promoter to ß-glucuronidase (GUS) reporter were used to study the GUS expression analysis in humic acid treated seedlings. This study demonstrates that humic acid treatment improved the shoot and root growth of wheat seedlings. The expression of several genes involved in auxin (Tryptophan Aminotransferase of Arabidopsis and Gretchen Hagen 3.2) and cytokinin (Lonely Guy3) biosynthesis pathways were up-regulated in humic acid-treated seedlings compared to the control. Furthermore, GUS expression analysis showed that bioactive compounds of humic acid stimulate endogenous auxin and cytokinin-like activities. This study is the first report in which using ARR5:GUS lines we demonstrate the biostimulants activity of humic acid.

The effects of soil compaction on wheat seedling root growth are specific to soil texture and soil moisture status

Soil structure is a crucial soil physical property that determines a soil's ability to support the growth and development of plants. Soil compaction modifies soil structure by reducing pore space between soil particles thereby leading to a denser soil fabric. This often limits root growth by increasing soil strength and penetration resistance requiring roots to increase the energy needed to elongate and explore deeper soil. Apart from soil compaction, soil moisture also plays an important role in determining how resistant soil is to root penetration. An understanding of how the synergy of both compaction and moisture content affect root growth is essential to improving plant productivity. We used wheat (Triticum aestivum) seedlings to investigate the differences in root architectural properties using X-ray Computed Tomography imaging under three different compaction levels (1.3, 1.5 and 1.7 Mg m−3) maintained at two different water contents (100% and 70% of field capacity). This was performed on soils of two different textures, a sandy loam and a sandy clay loam. Soil compaction to 1.7 g cm−3 significantly reduced root length, volume and surface area compared to lower compaction levels. Increased soil compaction also resulted in increased root growth angle in the sandy clay loam. Compaction reduced gas diffusivity in both soils (as determined by modelling). Soil moisture on the other hand had a significant impact on average root diameter; plants grown at 100% of field capacity had a higher average root diameter than those at 70% field capacity. Compaction up to 1.7 Mg m−3 adversely effected wheat root growth in both soil textures regardless of moisture content.

ФІЗІОЛОГО-БІОХІМІЧНІ ПОКАЗНИКИ ПРОРОСТКІВ ПШЕНИЦІ М’ЯКОЇ (TRITICUM AESTIVUM L.) ПРИ МОДЕЛЮВАННІ ВОДНОГО ДЕФІЦИТУ ЗА ДІЇ МЕТАБОЛІЧНО АКТИВНИХ СПОЛУК

The article presents a comparative description of the effect of metabolically active substances and their compositions on individual physiological and biochemical parameters of soft wheat in drought conditions. The study involved the use of 7 options for seed treatment: control (untreated seeds + distilled water); vitamin E solution (10-8M) - E; ubiquinone-10 solution (10-8M) - Q; methionine solution (0.001%) - M; paraoxybenzoic acid solution (PОBA) (0.001%) - P; MgSO4 solution (0.001%) - Mg; compositions of substances: vitamin E (10-8M) + ubiquinone-10 (10-8M) - EQ; vitamin E (10-8M) + methionine (0.001%) + POBA (0.001%) - EMР; vitamin E (10-8M) + methionine (0.001%) + POBA (0.001%) + MgSO4 (0.001%) - EMРMg. The experimental water deficiency was simulated by a 12% solution of PEG 6000.
 It was found that the germination of soft wheat seeds under the action of metabolically active substances in a solution of osmotically active substance PEG 6000 did not lead to a decrease in the germination energy of the experimental seeds compared to the control. Determination of germination of soft wheat seeds showed that treatment with Mg solution and compositions of EQ, EMР, EMРMg reduced the inhibitory effect of PEG 6000, showed a stimulating effect and increased seed germination. The highest seed germination in water-deficient conditions was found by treatment with EMРMg composition.
 Studies of the effect of metabolically active substances on the processes of rhizogenesis of soft wheat seedlings have shown that seeds’ treatment with the solution of methionine most effectively stimulated the formation of roots on wheat seedlings in conditions of water deficiency. Ubiquinone-10 solution stimulated linear root growth in conditions of water deficiency most effectively, exceeding the control by 16,9%, neutralizing the inhibitory effect of PEG 6000. High efficiency in stimulating linear root growth of wheat seedlings in drought conditions was observed after using the compositions EMР and EMPMg, and solutions of ubiquinone-10 and MgSO4. Ubiquinone-10 solution and composition EQ showed the best stimulating effect on the development of a shoot of soft wheat under water deficiency. Seeds treated with solutions of ubiquinone-10, MgSO4 and EQ had the highest rates of weight gain of roots. The seeds treated with ubiquinone-10 solution stimulated weight gain of the shoot more effectively under water deficiency (exceeded the control by 41.8%).
 Treatment of soft wheat seeds with compositions EQ and EMPMg stimulated the accumulation of free proline in wheat seedlings most effectively under water deficiency. Proline is an indicator of plant adaptation in conditions of slow water supply and increased drought resistance of soft wheat.
 Thus, seeds pre-sowing treatment with the studied metabolically active compounds and their compositions could be used as elements of technology in the cereals cultivation under water deficiency.

Changes in the concentrations and transcripts for gibberellins and other hormones in a growing leaf and roots of wheat seedlings in response to water restriction.

BackgroundBread wheat (Triticum aestivum) is a major source of nutrition globally, but yields can be seriously compromised by water limitation. Redistribution of growth between shoots and roots is a common response to drought, promoting plant survival, but reducing yield. Gibberellins (GAs) are necessary for shoot and root elongation, but roots maintain growth at lower GA concentrations compared with shoots, making GA a suitable hormone for mediating this growth redistribution. In this study, the effect of progressive drought on GA content was determined in the base of the 4th leaf and root tips of wheat seedlings, containing the growing regions, as well as in the remaining leaf and root tissues. In addition, the contents of other selected hormones known to be involved in stress responses were determined. Transcriptome analysis was performed on equivalent tissues and drought-associated differential expression was determined for hormone-related genes.ResultsAfter 5 days of applying progressive drought to 10-day old seedlings, the length of leaf 4 was reduced by 31% compared with watered seedlings and this was associated with significant decreases in the concentrations of bioactive GA1 and GA4 in the leaf base, as well as of their catabolites and precursors. Root length was unaffected by drought, while GA concentrations were slightly, but significantly higher in the tips of droughted roots compared with watered plants. Transcripts for the GA-inactivating gene TaGA2ox4 were elevated in the droughted leaf, while those for several GA-biosynthesis genes were reduced by drought, but mainly in the non-growing region. In response to drought the concentrations of abscisic acid, cis-zeatin and its riboside increased in all tissues, indole-acetic acid was unchanged, while trans-zeatin and riboside, jasmonate and salicylic acid concentrations were reduced.ConclusionsReduced leaf elongation and maintained root growth in wheat seedlings subjected to progressive drought were associated with attenuated and increased GA content, respectively, in the growing regions. Despite increased TaGA2ox4 expression, lower GA levels in the leaf base of droughted plants were due to reduced biosynthesis rather than increased catabolism. In contrast to GA, the other hormones analysed responded to drought similarly in the leaf and roots, indicating organ-specific differential regulation of GA metabolism in response to drought.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12870-022-03667-w.

Changes of oxidative metabolism in the roots of wheat (Triticum aestivum L.) seedlings in response to elevated ammonium concentrations

To elucidate the response of oxidative metabolism, triggered by elevated ammonium (NH4+) concentrations, on root growth of wheat seedlings, Yumai 49 (NH4+-tolerant) and Lumai 15 (NH4+-sensitive) cultivars were supplied with either 5.0 mmol L−1 NH4+-N (EAC) or 5.0 mmol L−1 NO3–-N (CON) under hydroponic conditions. Root growth in both cultivars was significantly reduced under EAC, and the negative effect was greater in Lumai 15. EAC enhanced the activities of monodehydroascorbate reductase and dehydroascorbate reductase in the roots of both cultivars, while it decreased ascorbic acid (ASA) content and GDP-mannose pyrophosphorylase (GMPase) activity at the 12th day after treatment in Lumai 15 by 62.0 and 71.4%; and in Yumai 49 by 38.8 and 62.2%, respectively, indicating that the regeneration of ASA was increased, but the biosynthesis of ASA was reduced under EAC treatment. Moreover, EAC increased DHA/ASA, reactive oxygen species (ROS), and malondialdehyde contents, as well as antioxidant enzyme activities in the roots of both cultivars. Relatively greater increases in ROS and soluble sugar, and lower antioxidant enzyme activities in Lumai 15 indicate severe disruption of oxidative metabolism when compared to Yumai 49. Results reveal that the reduction of ASA biosynthesis via decreased GMPase activity under the EAC condition probably acts as a trigger for accumulated ROS and imbalanced redox status, resulting in root growth inhibition during wheat seedling growth stage. Yumai 49, being an NH4+ -tolerant cultivar, had the stronger capacity to protect itself from oxidative stress, which allowed it to retain a lower DHA to ASA ratio by maintaining a better redox homeostasis than could be maintained in the NH4+ -sensitive cultivar Lumai 15.

Hydrogen peroxide mediates triclosan-induced inhibition of root growth in wheat seedlings

Triclosan, an extensively used antimicrobial agent, enters agroecosystems when sewage sludge and reclaimed water are applied to agricultural fields, and may trigger a series of plant physiological and biochemical responses. However, few studies have investigated the mechanism by which plant development is affected by triclosan. Here, microscopic, pharmacological and biochemical analyses, and histochemical dye staining were used to explore the effects of triclosan on root growth in wheat plants. Exposure to triclosan inhibited root elongation, and significantly triggered hydrogen peroxide (H2O2) production and lipid peroxidation in wheat roots. The inhibition of root growth by triclosan was reversed by dimethylthiourea, a H2O2 scavenger, indicating that alterations of endogenous H2O2 concentrations in root cells were likely linked to triclosan-induced root growth inhibition. The addition of butylated hydroxyanisole, a lipophilic antioxidant, during triclosan treatment completely prevented the increase of lipid peroxidation, but did not alleviate triclosan-induced reduction of root growth. In triclosan-treated wheat roots, the level of indole-3-acetic acid decreased by 68.3%, while the contents of two indole-3-acetic acid oxidative metabolites, indole-3-aldehyde and indole-3-carboxylic acid, increased by 71.3% and 314.4%, respectively. Moreover, the oxidation of auxin induced by triclosan in wheat roots was prevented by dimethylthiourea. These results together suggested that the triclosan-enhanced production of H2O2 induced auxin oxidation, thus leading to the suppression of root growth. Findings of this study improve our mechanistic understanding on how antimicrobial agents such as triclosan affect plant root growth.

Elevated CO2-induced production of nitric oxide differentially modulates nitrate assimilation and root growth of wheat seedlings in a nitrate dose-dependent manner.

Wheat is a major staple food crop worldwide contributing approximately 20% of total protein consumed by mankind. The nitrogen and protein concentration of wheat crop and grain often decline as a result of exposure of the crop to elevated CO2 (EC). The changes in nitrogen (N) assimilation, root system architecture, and nitric oxide (NO)-mediated N signaling and expression of genes involved in N assimilation and high affinity nitrate uptake were examined in response to different nitrate levels and EC in wheat. Activity of enzyme nitrate reductase (NRA) was downregulated under EC both in leaf and root tissues. Plants grown under EC displayed enhanced production of NO and more so when nitrate supply was high. Based on exogenous supply of NO, inhibitors of NO production, and NO scavenger, regulatory role of NO on EC mediated changes in root morphology and NRA was revealed. The enhanced NO production under EC and high N levels negatively regulated the transcript abundance of NR and high affinity nitrate transporters (HATS).

Determination of zinc oxide nanoparticles toxicity in root growth in wheat (Triticum aestivumL.) seedlings

The effect of zinc oxide nanoparticles (ZnONPs) was studied in wheat (Triticum aestivum L.) seedlings under in vitro exposure conditions. To avoid precipitation of nanoparticles, the seedlings were grown in half strength semisolid Murashige and Skoog medium containing 0, 50, 100, 200, 400 and 500 mg L(-1) of ZnONPs. Analysis of zinc (Zn) content showed significant increase in roots. In vivo detection using fluorescent probe Zynpyr-1 indicated accumulation of Zn in primary and lateral root tips. All concentrations of ZnONPs significantly reduced root growth. However, significant decrease in shoot growth was observed only after exposure to 400 and 500 mg L(-1) of ZnONPs. The reactive oxygen species and lipid peroxidation levels significantly increased in roots. Significant increase in cell-wall bound peroxidase activity was observed after exposure to 500 mg L(-1) of ZnONPs. Histochemical staining with phloroglucinol-HCl showed lignification of root cells upon exposure to 500 mg L(-1) of ZnONPs. Treatment with propidium iodide indicated loss of cell viability in root tips of wheat seedlings. These results suggest that redox imbalances, lignification and cell death has resulted in reduction of root growth in wheat seedlings exposed to ZnONPs nanoparticles.

Influence of Merosesquiterpenoids from Marine Sponges on Seedling Root Growth of Agricultural Plants

The impact of the merosesquiterpenoids avarol (1), avarone (2), 18-methylaminoavarone (3), melemeleone A (4), isospongiaquinone (5), ilimaquinone (6), and smenoquinone (7), isolated from marine sponges of the Dictyoceratida order, was studied on the root growth of seedlings of buckwheat (Fagopyrumesculentum Moench), wheat (Triticumaestivum L.), soy (Glycine max (L.) Merr.), and barley (Hordeumvulgare L.). Compounds 2and 6 were effective for the root growth of wheat seedlings, compound 3 stimulated the root growth of seedlings of buckwheat and soy, compound 4 affected the roots of barley seedlings, and compound 5 stimulated the root growth of seedlings of buckwheat and barley. Compounds 1 and 7 showed no activity on the root growth of the seedlings of any of the studied plants. The stimulatory effect depends on the chemical structure of the compounds and the type of crop plant.

Interaction of nitric oxide and reactive oxygen species and associated regulation of root growth in wheat seedlings under zinc stress

The inhibition of root growth was investigated in wheat seedlings exposed to 3mM zinc (Zn). Zn treatment with or without 250µM 2-phenyl-4,4,5,5,-tetrame-thylimidazoline-3-oxide-1-oxyl (PTIO) or 10µM diphenylene iodonium (DPI) significantly inhibited growth, increased malondialdehyde content and lowered cell viability in roots. The most prominent changes of these three parameters at Zn+DPI treatment could be partly blocked by high PTIO concentration (1mM). The production of nitric oxide (NO) and hydrogen peroxide (H2O2) influenced each other under different treatments, with the highest NO level and the highest H2O2 accumulation in Zn+DPI-treated roots. Compared with Zn-stressed roots, catalase, soluble peroxidase (POD), ascorbate peroxidase and superoxide dismutase decreased in Zn+DPI-treated roots, suggesting that ROS generation from plasma membrane (PM) NADPH oxidase was associated with the regulation of antioxidant enzyme activities. Additionally, Zn-treated roots exhibited significant decreases in cell wall-bound POD, diamine oxidase and polyamine oxidase activities. Our results suggested that Zn-induced effects on root growth resulted from NO interaction with H2O2 and that Zn+DPI-induced strongest inhibition could be explained by the highest increase in the endogenous NO content and the reduction of extracellular ROS production.

Cerebroside C increases tolerance to chilling injury and alters lipid composition in wheat roots.

Chilling tolerance was increased in seed germination and root growth of wheat seedlings grown in media containing 20 µg/mL cerebroside C (CC), isolated from the endophytic Phyllosticta sp. TG78. Seeds treated with 20 µg/mL CC at 4°C expressed the higher germination rate (77.78%), potential (23.46%), index (3.44) and the shorter germination time (6.19 d); root growth was also significantly improved by 13.76% in length, 13.44% in fresh weight and 6.88% in dry mass compared to controls. During the cultivation process at 4°C for three days and the followed 24 h at 25°C, lipid peroxidation, expressed by malondialdehyde (MDA) content and relative membrane permeability (RMP) was significantly reduced in CC-treated roots; activities of lipoxygenase (LOX), phospholipid C (PLC) and phospholipid D (PLD) were inhibited by 13.62–62.26%, 13.54–63.93% and 13.90–61.17%, respectively; unsaturation degree of fatty acids was enhanced through detecting the contents of CC-induced linoleic acid, linolenic acid, palmitic acid and stearic acid using GC-MS; capacities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) were individually increased by 7.69–46.06%, 3.37–37.96%, and −7.00–178.07%. These results suggest that increased chilling tolerance may be due, in part, to the reduction of lipid peroxidation and alternation of lipid composition of roots in the presence of CC.

Potential allelopathic effects of Xanthium italicum Moretti on wheat.

The allelopathic potential of invasive Xanthium italicum Moretti on seedling growth of wheat (Triticum aestivum Linn) was investigated. Aqueous (0.05 g/ml) and ethanol (1 mg/ml) extracts reduced root elongation of wheat seedlings by 71 and 87%, respectively; chloroform fraction of the ethanol extract exhibited the strongest phytotoxic effect as compared to other fractions, inhibiting root growth of wheat seedlings by 95% at 1 mg/ml. Incorporation of X. italicum plant residues (20, 50 and 100 g/kg soil) into soils affected not only photosynthetic pigment content, but also photosynthetic parameters of wheat seedlings. Chlorophyll a, b and carotenoid contents of wheat seedlings decreased significantly when plant residues were applied at 100 g/kg soil. Net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductivity (gs) decreased greatly when seedlings were treated with plant residues at 20, 50 and 100 g/kg soil, whereas CO2 concentration (Ci) increased significantly at 50 and 100 g plant residue/kg soil. Shoot length, fresh and dry weight were also significantly affected starting from 20 g plant residue/kg soil treatment in a dose-dependent manner. Furthermore, our results indicated that soil conductivity, soil pH and soil nutrients were unlikely responsible for the aforementioned changes. Our results suggest that allelopathy might contribute to the invasion success of X. italicum, and its invasion could possibly pose potential threat to wheat production in China. Key words: Allelopathy, phytotoxin, wheat, Xanthium italicum.

Zinc induced phytotoxicity mechanism involved in root growth of Triticum aestivum L.

This study investigated the inhibition mechanism of root growth in wheat seedlings when exposed to different zinc (Zn) concentrations. All applied Zn concentration did not affect seed germination, but reduced root length; in contrast, only Zn at 3mM inhibited significantly the growth of shoot. The loss of cell viability and the significant increases of lignification as well as the increases of hydrogen peroxide (H2O2), superoxide radical (O2−) and malondialdehyde levels were observed in the root tissue exposed to Zn treatment. And also, Zn stress led to the inhibition of cell-wall bound peroxidase. Moreover, NADPH oxidase inhibitor diphenylene iodonium could block greatly the elevation of O2− generation in Zn-treated roots. Therefore, the increased H2O2 generation was dependent on the extracellular O2− production derived from plasma membrane NADPH oxidase. In addition, the loss of cell viability and the significant increases of lignification in response to the highest Zn concentration may be associated with the remarkable reduction of root growth in wheat seedlings.

Genetic control of wheat seedling root growth

Wheat cultivars should have long primary roots to allow good crop establishment, considering the short crop establishment season (April) in the State of São Paulo, Brazil, where the occurrence of water stress is frequent. This paper demonstrates the control and type of inheritance of the primary root growth trait. Crosses were made between genotypes, BH-1146 and KAUZ "S"/IAC-24 M4 with strong and reduced primary root growth, respectively. F2 and F3 generation seeds from these crosses and F2 generation seeds from the backcrosses of both parents were also obtained. Seedlings from these genotypes plus the parentals were evaluated in relation to primary root growth in complete nutrient solutions containing 3.875 mg L-1 phosphorus, at pH 4.0 and a temperature of 25 ± 1°C for 10 days. Control of the primary root growth trait was demonstrated to have quantitative inheritance. The degrees of dominance showed that the genes for strong root growth had a partially recessive behavior. Heterosis and heterobeltiosis values were negative. The estimated broad-sense heritability for root growth indicated that a great part of the observed variation was of genetic origin. The narrow-sense heritability indicated that a great part of the total genetic variability in relation to the trait under consideration is due to a small number of genes. Considering the estimated coefficient of determination, selection for strong root growth would be effective even when made in the early segregant generations after the cross.

Cell-wall extension as a mode of action of coal-derived humates

A coal-derived sodium humate (HANa) was found to stimulate root growth of wheat seedlings ( Triticum aestivum L.). A study of possible modes of action of HANa showed that (i) by chelating out ferrous iron, HANa sequestered a key participant from the reaction whereby proline is hydroxylated to hydroxyproline, resulting in significantly less hydroxyproline being formed in the cell walls of roots treated with HANa, and that (ii) HANa inhibited the activity of peroxidase and IAA oxidase, the inhibition of peroxidase being of the uncompetitive type. Since these effects have implications for the ability of root cells to undergo extension, it is proposed that they provide explanations for the stimulatory effect of HANa on growth.

98/03802 Root growth and trace element uptake in acid soils treated with coal combustion byproducts

Root growth of wheat seedlings (Triticum aestivum) and trace element levels in ryegrass (Lolium multiorum) were determined in acid soils treated with 1.25 to 80 g kg−1 of eight coal combustion by-products: fly ash (FA), bed ash (BA), cyclone ash (CA), limestone injection residue ( LIMB), spray drier residue (SD), scrubber sludge (CS), stabilized scrubber sludge (SS) and gypsum-like material (G). Low application rates of by-products did not inhibit wheat seedling root growth. FA and G did not limit root growth at any application rate while BA, LIMB, SD and CA inhibited root growth at high rates. Ryegrass concentrations of Cu, Zn, Ni, Pb, Cd and Cr were similar in treated and untreated soil. B, Se, As and Mo were increased in ryegrass grown in treated soil, but Se from FA treatments was the only potential food chain risk from a single application of these materials. The G material would seem to be the most benign for land application because it improved root growth without producing elevated trace element levels in plant material or soil solution.

Root growth and trace element uptake in acid soils treated with coal combustion by-products

Root growth of wheat seedlings ( Triticum aestivum) and trace element levels in ryegrass ( Lolium multiorum) were determined in acid soils treated with 1.25 to 80 g kg −1 of eight coal combustion by-products: fly ash (FA), bed ash (BA), cyclone ash (CA), limestone injection residue ( LIMB), spray drier residue (SD), scrubber sludge (CS), stabilized scrubber sludge (SS) and gypsum-like material (G). Low application rates of by-products did not inhibit wheat seedling root growth. FA and G did not limit root growth at any application rate while BA, LIMB, SD and CA inhibited root growth at high rates. Ryegrass concentrations of Cu, Zn, Ni, Pb, Cd and Cr were similar in treated and untreated soil. B, Se, As and Mo were increased in ryegrass grown in treated soil, but Se from FA treatments was the only potential food chain risk from a single application of these materials. The G material would seem to be the most benign for land application because it improved root growth without producing elevated trace element levels in plant material or soil solution.

Growth retardant activity of paclobutrazol enantiomers in wheat seedlings

The resolved enantiomers of paclobutrazol appeared to have different primary modes of action as plant growth retardants in rht3 (tall) wheat seedlings. 2S,3S-Paclobutrazol reduced shoot growth more effectively than root growth, whereas the opposite was the case with the 2R,3R-enantiomer. Low concentrations (0.03–1.0 μM) of 2S,3S-paclobutrazol specifically inhibited gibberellin A1 (GA1) production in Rht3 (dwarf) seedlings without affecting shoot growth, confirming that inhibition of GA biosynthesis is the primary mode of action of this enantiomer. Reductions in shoot growth of rht3 (tall) wheat treated with 2S,3S-paclobutrazol were associated with reductions in GA1 content, an effect that could be reversed by gibberellic acid (GA3) application, showing that GAs are important regulators of light-grown shoot growth in wheat. The inhibition of root growth of wheat seedlings following treatment with 2R,3R-paclobutrazol was associated with a decline in de novo synthesis of major sterols, a decrease in stigmasterol: sitosterol ratio and an accumulation of the 14α-methyl sterol, obtusifoliol. Concentrations >3 μM 2S,3S-paclobutrazol also affected de novo sterol production in wheat roots, suggesting that root growth is more responsive to interference with sterol than GA biosynthesis. There was a decline in abscisic acid (ABA) content in Rht3 (dwarf) shoots treated with relatively high concentrations of 2S,3S-paclobutrazol but no effect with its optical isomer.

Soil acidity effects on wheat seedling root growth

Abstract Soft red winter wheat (Triticum aestivum L. cv Hart) was used as a test crop in a bioassay technique to assess acid soil chemical constraints in major hill land soils of the Appalachian Region. Seedling root growth was related to amounts and forms of Al in soil solution and Al extracted by 0.01M CaCl2, 1M KC1, 0.5M CuCl2, and 0.33M LaCl3. Aluminum determined in the various extractants, total soil solution Al and soil solution Al reacting with 8‐hydroxy‐quinoline, pyrocatechol violet, and aluminon showed large differences in root growth prediction ability. In general, Al extracted by 0.01M CaCl2 was a good predictor of root growth. Root elongation was more inhibited in subsurface horizons than in surface horizons. Although surface horizons had the lowest mean pH, the presence of high levels of exchangeable cations tended to ameliorate the Al toxicity. The root bioassay technique adapted here should be useful in assessing the potential Al toxicity of diverse soil types.