Rice Growth Inhibition Research Articles

Optimum water depth for suppressing late watergrass growth with minimizing rice growth inhibition under different temperature conditions

Optimum water depth for suppressing late watergrass growth with minimizing rice growth inhibition under different temperature conditions

Candidate Genes Involved in Tolerance to Fenoxaprop-P-Ethyl in Rice Induced by Isoxadifen-Ethyl Hydrolysate

The metabolic resistance of plants to herbicides is similar to the herbicide metabolism process accelerated by safeners. The tolerance to fenoxaprop-P-ethyl (FE) is distinct among different varieties of rice in which phytotoxicity forms easily, resulting in the restricted use of FE in paddy. Safener effectively resolves this issue. This study showed that rice 9311 and Meixiangzhan No. 2 (MXZ) had different tolerance mechanisms to FE. Isoxadifen-ethyl hydrolysate (IH) alleviated FE the inhibition of rice growth. Transcriptome sequencing revealed numerous differentially expressed genes (DEGs) between the two varieties. A total of 31 metabolic enzyme genes related to herbicide detoxification were screened by analyzing the DEGs in different rice varieties or treatments. The results of the quantitative reverse transcription polymerase chain reaction indicated that 12 genes were potential metabolic genes resistant to FE in rice. Additionally, the enhanced expression of GSTU6, DIMBOA UGT BX8, and ABCG39 was confirmed to be induced by safener. Taken together, our results demonstrated that the induced expression of these three genes might be crucial for resistance to herbicide phytotoxicity in crops. These results may help us to understand herbicide metabolism in crops and to develop novel strategies for the safe use of herbicides.

Effects of microplastics on arsenic uptake and distribution in rice seedlings

The potential of microplastics (MPs) and nanoplastics (NPs) to act as a carrier for heavy metals derived from the environment is of rising concern to the health of global ecosystems. Here, we investigated the effects of particle size of polystyrene micro/nano plastics on the uptake, accumulation, and toxicity of As in rice seedlings in a hydroponic system. Significant differences in As uptake and accumulation in different plant tissue were observed between the plants co-exposed to 82 nm NPs + As and 200 nm MPs + As. The NPs + As co-exposure led to higher As accumulation in rice leaves (12.4–36.7 %), while larger sized MPs + As(V) treatment reduced As accumulation in rice leaves. Furthermore, the co-exposure of NPs/MPs + As mitigated the rice growth inhibition caused by As toxicity. These results will provide insight into elucidating the potentially effects of nano/microplastics on As uptake and accumulation in crop plants for assessing the hazards of micro-and nanoplastics as pollutants in the food chain and environment.

Physiological causes of transplantation shock on rice growth inhibition and delayed heading

Transplanting is an important rice cultivation method; however, transplanting shock commonly affects grain yield, and the mechanisms underlying the inhibition of growth, development, and delayed heading caused by transplanting shock have not yet been clearly elucidated. Here, we investigated the effects of seedling age, temperature, and root damage during transplanting on growth, development, and time to heading, both under artificially controlled and natural day length. Additionally, we investigated the impact of seedling root growth space and the potential mitigating effects of residual seed nutrients on young transplanted seedlings. The delay in heading in transplanted versus directly seeded plants was affected more by growth inhibition during the seedling period than by root damage during transplanting. However, root damage had an effect on the inhibition of leaf and tiller development, and the ratio of leaves to tillers increased because tiller development was inhibited more by transplanting shock compared with leaf development. Based on these findings, we propose factors reflecting the delay in growth due to transplanting shock that should be included for more accurate rice phenology modeling and suggest advantageous seeding conditions and transplanting methods for improved rice cultivation and yield in response to climate change.

Boron application mitigates Cd toxicity in leaves of rice by subcellular distribution, cell wall adsorption and antioxidant system

Cadmium (Cd) is a hazardous heavy metal and some of its negative effects include inhibition of rice growth, while also accumulates in the rice grains. Boron (B) has been implicated in mitigating Cd toxicity. Nevertheless, a few studies have been performed up to now to evaluate whether B could encourage Cd tolerance in rice by regulating Cd adsorption on cell walls (CW) in leaves of rice. The current experiment used different concentrations of B (0, 20, and 30 µM) along with 50 µM Cd to rice seedlings. The results indicate that single treatment of Cd significantly inhibited root and shoot growth and caused leaf chlorosis. However, B application at 20, and 30 µM reduced Cd concentrations in the roots by 66% and 77%, and in shoots by 72% and 83%, respectively, and increased plant development. Boron supply at 30 µM increased Cd in leaf CW fraction by 79% and decreased Cd by 64% in the organelle fraction. Moreover, B addition regulated the antioxidant system and decreased malonaldehyde contents (45%) in rice leaves. The present study demonstrates that B reduces Cd translocation and facilitates Cd adsorption on CW and regulates an efficient antioxidant system in rice leaves.

Effects of ionic liquid [N4444] AOT on rice seedling growth cytomembrane damage and rhizobacteria resistance.

Ionic liquids (ILs) are solvents composed of ions, containing a large asymmetric cation with an anion. With increasing and widespread applications, the toxic effects of ILs have been considerable in recent years. This study explained the effects of the new functional ionic liquids [N4444] bis(2-ethylhexyl) sulfonyl succinate (AOT) on rice seedling and the growth of rhizobacteria. The rice seeds pretreated by [N4444] AOT revealed that it exhibited a significant negative impact on rice seedlings. The inhibition of rice growth increased with increasing concentration. When the concentration of [N4444] AOT increased to 0.25 and 0.5 mL L-1, the germination potential decreased by 40.0% and 86.3%, respectively, compared with the control. The germination potential and germination rate of rice were reduced, and the stress effect of ionic liquid on the root parts was higher than the aerial parts. The biomass of rice seedlings was decreased by 34.8 to 91.2%. Iodinic propane staining showed that by increasing concentration, the root cell cytomembrane damage level was increased and also changed the cell shapes, especially under 0.25 mg L-1 concentration stress. However, rhizobacteria of rice showed strong [N4444] AOT-resistant characteristics when the concentration was reached to 120 mg L-1. The ILs even more promoted the growth of Enterobacter sp. NP1142 and Pantoea sp. BR23. It was indicated that IL [N4444] AOT can be degraded easily by rhizobacteria to eliminate the eco-risk of ILs.

Unraveling the Genetic Elements Involved in Shoot and Root Growth Regulation by Jasmonate in Rice Using a Genome-Wide Association Study

BackgroundDue to their sessile life style, plant survival is dependent on the ability to build up fast and highly adapted responses to environmental stresses by modulating defense response and organ growth. The phytohormone jasmonate plays an essential role in regulating these plant responses to stress.ResultsTo assess variation of plant growth responses and identify genetic determinants associated to JA treatment, we conducted a genome-wide association study (GWAS) using an original panel of Vietnamese rice accessions. The phenotyping results showed a high natural genetic variability of the 155 tested rice accessions in response to JA for shoot and root growth. The level of growth inhibition by JA is different according to the rice varieties tested. We conducted genome-wide association study and identified 28 significant associations for root length (RTL), shoot length (SHL), root weight (RTW), shoot weight (SHW) and total weight (TTW) in response to JA treatment. Three common QTLs were found for RTL, RTW and SHL. Among a list of 560 candidate genes found to co-locate with the QTLs, a transcriptome analysis from public database for the JA response allows us to identify 232 regulated genes including several JA-responsive transcription factors known to play a role in stress response.ConclusionOur genome-wide association study shows that common and specific genetic elements are associated with inhibition of shoot and root growth under JA treatment suggesting the involvement of a complex JA-dependent genetic control of rice growth inhibition at the whole plant level. Besides, numerous candidate genes associated to stress and JA response are co-located with the association loci, providing useful information for future studies on genetics and breeding to optimize the growth-defense trade-off in rice.

Effects of straw returning on rice growth and yield under water-saving irrigation

ABSTRACT Straw returning (SR) is an important means of straw utilization, which has been tested and is helpful for improving soil fertility and crop production. However, the effects of SR on plant growth and yield of paddy rice (Oryza sativa L. subsp. japonica Kato) under water-saving irrigation (WSI) are rarely investigated. In the 2015 and 2016 rice seasons, field experiments were conducted with four treatments, namely controlled irrigation with conventional fertilization (CI- CF), controlled irrigation with straw returning (CI-SR), flooding irrigation with conventional fertilization (FI-CF), and flooding irrigation with straw returning (FI-SR). The objective of the present study was to investigate the response of plant height, number of tillers, biomass, and yield to SR and irrigation management. Results indicated that SR enhanced rice yield on average by 7.9% and 7.5% and improved irrigation water use efficiency (IWUE) by 6.3% and 8.3% in 2015 and 2016, respectively. The CI-SR combination significantly increased IWUE compared with FI-CF. These results suggested that SR could offset the inhibition of rice growth caused by CI, and the CI-SR combination could be an effective measure to enhance soil fertility, maintain the rice field, and increase IWUE. Furthermore, rice growth (plant height, number of tillers, and biomass) was slightly inhibited by SR during the first 20 d of the rice season, but increased after the jointing stage (approximately 40 d after transplanting). This implied that diverting some top-dressed chemical N fertilizer into basal application may be necessary for fertilizer management to better meet crop nutrient uptakes in rice fields with SR application, especially with CI.

Accumulation of ammonium and reactive oxygen mediated drought-induced rice growth inhibition by disturbed nitrogen metabolism and photosynthesis

Nitrogen (N) deficiency and drought are two key limiting factors for rice production worldwide, but the relationship of drought stress with N homeostasis in rice is rarely advanced. The aim of this study was to dissect the physiological effects of drought stress on rice growth that coupled unbalanced N metabolism. Water-deficient stress (WD) limited stomatal aperture function and activity of Rubisco carboxylase to photosynthesis. The rate of total electron transport (Jt) and the electron to carboxylation (Jc) were considerably decreased, whereas the proportion of e− flow to photorespiration was stimulated by WD, especially at 1600 μmol m−2 s−1 PPFD. Concurrently, the expressions of glycolate oxidase genes (GOX1, GOX5) and glycine decarboxylase complex (GDCH, GDCP and GDCT) were significantly induced in leaves of WD treatment, which led to the accumulation of reactive oxygen species in leaves. With the photosynthetic change, nitrate uptake and reduction were suppressed. Moreover, the enhanced photorespiration generated excess NH3 accumulation in leaves and stimulated the expressions of GS1;1, GS1;2 and GS2, which were tightly coupled with the expressions of PEPC1 and PEPC2 under WD stress. Our results suggest that the inhibited nitrate reduction associated with diminished electron transport rate, and the photorespiration-associated accumulation of hydrogen peroxide and NH3 were critical in the drought-induced rice growth inhibition.

Ethylene Mediates Alkaline-Induced Rice Growth Inhibition by Negatively Regulating Plasma Membrane H+-ATPase Activity in Roots.

pH is an important factor regulating plant growth. Here, we found that rice was better adapted to low pH than alkaline conditions, as its growth was severely inhibited at high pH, with shorter root length and an extreme biomass reduction. Under alkaline stress, the expression of genes for ethylene biosynthesis enzymes in rice roots was strongly induced by high pH and exogenous ethylene precursor ACC and ethylene overproduction in etol1-1 mutant aggravated the alkaline stress-mediated inhibition of rice growth, especially for the root elongation with decreased cell length in root apical regions. Conversely, the ethylene perception antagonist silver (Ag+) and ein2-1 mutants could partly alleviate the alkaline-induced root elongation inhibition. The H+-ATPase activity was extremely inhibited by alkaline stress and exogenous ACC. However, the H+-ATPase-mediated rhizosphere acidification was enhanced by exogenous Ag+, while H+ efflux on the root surface was extremely inhibited by exogenous ACC, suggesting that ethylene negatively regulated H+-ATPase activity under high-pH stress. Our results demonstrate that H+-ATPase is involved in ethylene-mediated inhibition of rice growth under alkaline stress.

Non‐protein thiols and glutathione S‐transferase alleviate Cd stress and reduce root‐to‐shoot translocation of Cd in rice

AbstractA hydroponic experiment was conducted to investigate the dynamic variations of cadmium (Cd) uptake and transport, non‐protein thiols (NPT) and glutathione (GSH) concentrations, glutathione S‐transferase (GST) activity and lipid peroxidation under Cd stress in order to clarify the role of NPT and GST in reducing Cd toxicity and translocation in rice (Oryza sativa L.). Cadmium accumulation was initially fast and then slowed down with increasing time of Cd exposure. However, the rice growth inhibition and lipid peroxidation were not intense until 5d after Cd treatment, even though Cd kept accumulating in root and shoot, suggesting that Cd may be effectively detoxified. The concentrations of NPT in root increased gradually until 5d after Cd stress, whereas those in shoot showed no significant changes. The concentration of shoot GSH was progressively enhanced upon Cd treatment, while it gradually declined in root after an initial increase. The GST activity varied similarly in root and shoot, reaching the maximum level on 3rd day, followed by a significant decrease 5 d after Cd application. Significant increases of lipid peroxidation and root‐to‐shoot translocation on 7th day indicate that the equilibrium in Cd‐thiol interaction in rice might be disturbed upon the prolonged Cd exposure. In summary, our results suggest that Cd may be retained and detoxified in rice root through chelation with thiol compounds and subsequent sequestration.

Strain competition and agar affect the interaction of rhizobia with rice

Competition assays with Sinorhizobium meliloti 1021 and its GFP-labelled pSymA cured and deleted derivatives, SmA818 and SmA146, demonstrated that Sm1021 could still inhibit rice seedling growth even when outnumbered by a large excess of the noninhibitory cured or deleted strain. The wild-type strain Sm1021 also inhibited the growth of its noninhibitory pSymA-cured strain SmA818(gfp) and its pSymA-deleted strain SmA146(gfp) in a manner suggesting that Sm1021 produced a bacteriocin-like substance. The production of, and resistance to, this substance seemed to be pSymA-associated, but it was not the cause of killing in competition experiments on rice, suggesting that the killing of SmA818(gfp) and SmA146(gfp) was medium dependent. The addition of agar in liquid F10 medium at concentrations < or = 0.4% (m/v) abolished the rice growth inhibition of strain Sm1021 and Sm1021(gfp). The increased medium viscosity at higher agar concentrations decreased the diffusion of gases and small molecules through the media. Thus, the low agar concentrations may mimic waterlogged soil conditions leading to the production of inhibitory compounds by the bacterial strains under microaerobic conditions.

Rhizobium-Initiated Rice Growth Inhibition Caused by Nitric Oxide Accumulation

Isolates of Rhizobium leguminosarum bv. trifolii (the clover root-nodule endosymbiont) from the Nile River delta have been found to infect rice roots and colonize the intercellular spaces of the rice roots. Some of these isolates inhibit rice seedling growth but one in particular, R4, has been found in rice roots which develop and grow normally. We present evidence that the induced growth inhibition is due to a toxic accumulation of nitric oxide (NO), from the reduction of nitrate, and suggest that the reason that R4 does not inhibit rice root growth is because it is capable of completing the reduction of NO through to nitrogen gas. Thus, strain R4 is a candidate for engineering into a future biological nitrogen fixation system within these roots.

Plasmid‐associated genes in the model micro‐symbiont Sinorhizobium meliloti 1021 affect the growth and development of young rice seedlings

Sinorhizobium meliloti strain 1021 and its closely related strain Rm2011 inhibit rice seedling (Oryza sativa L. cv. Pelde) growth and development under certain rice-growing conditions. Experiments showed that inoculation of seedlings with approximately less than 10 cells of 1021 was sufficient to cause this inhibition. By using a series of plasmid-cured and plasmid-deleted derivatives of Rm2011, it was found that interactions between genes encoded on pSymA, and possibly pSymB, of Rm2011, affected rice growth and development by affecting both/either the plant and/or the bacteria. Further studies found that genes potentially related to indole-3-acetic acid (IAA) synthesis and nitrate metabolism, encoded on pSymA, were involved in rice growth inhibition in Sm1021- and Sm2011-treated rice seedlings. We conclude that the rice growth inhibition by S. meliloti Sm1021 is pSymA-associated and is induced by environmental nitrate.

Gas chromatography-mass spectrometry analysis of indoleacetic acid and tryptophan following aqueous chloroformate derivatisation of Rhizobium exudates

A new method for preparing alkyl esters of indole-3-acetic acid (IAA) in aqueous solution is adapted from the chloroformate method originally described by Hušek for the analysis of amino acids. This method has the significant advantage of avoiding the generation and use of diazomethane, and is done in aqueous solution without the need to dry the sample with concomitant non-specific losses of IAA. The effectiveness of this method is demonstrated by its use in an isotope dilution gas chromatography-mass spectrometry (GC-MS) assay of IAA and l-tryptophan (Trp) in the culture supernatant of a series of Sinorhizobium meliloti and Rhizobium leguminosarum bv. trifolii strains that can interact with rice to either enhance or inhibit rice plant growth. We were testing the hypothesis that the rice growth inhibition was related to the biosynthesis of IAA. It was found that S. meliloti and Rhizobium strains produced high amounts of IAA in Trp supplemented BIII minimal medium compared to BIII media. All the strains produced more than the minimum amount of IAA required to inhibit rice growth and thus IAA is not the major inhibitory factor of rice seedling growth from S. meliloti and Rhizobium strains.

Rhizobium plasmids are involved in the inhibition or stimulation of rice growth and development

This paper originates from an address at the 8th International Symposium on Nitrogen Fixation with Non-Legumes, Sydney, NSW, December 2000 We examined growth responses of rice seedlings (Oryza sativaL. cv. Pelde) to specific Rhizobium strains and their mutants, to investigate the molecular basis of colonization and the stimulation or inhibition of rice growth and development by rhizobia. Inoculation experiments with rice seedlings showed that specific Rhizobium isolates of these rice-associated and legume-associated rhizobia could either promote, inhibit, or have no influence on rice plant growth. There are genes on certain plasmids of Rhizobium leguminosarum bv. trifolii and R. leguminosarum bv. viciae that affect the growth and development of rice root morphology. Additionally, we found that bacteria can intimately associate with, and enter into, rice seedling roots by alternative mechanisms to those encoded by the symbiotic (pSym) and the tumour-inducing (Ti) plasmids. Investigations suggest an involvement of the phytohormone auxin, and possibly nitrate, in this complex rice–Rhizobium interaction.

オキサジアゾン乳剤による新しい水田除草法の確立に関する研究

The present study was undertaken with a view to clarifying the properties of oxadiazon as a herbicide for transplanted rice and to developing effective application methods best suited to its properties.Weed control effect of the herbicide on barnyardgrass was evaluated and the following results were obtained.1) Oxadiazon application was most effective as a pre-emergence treatment. Weed control effect of the herbicide was reduced with the progression of the growth stages of barnyardgrass.2) Oxadiazon was able to control barnyardgrass effectively in flooded water even at a concentration as low as 0.05ppm.3) The deeper the incorporation of oxadiazon in soil, the lower was the herbicidal activity.4) In the soil incorporation treatment, oxadiazon was effective in the control of barnyardgrass at the pre-emergence stage up to a depth of 2-3cm from the soil surface. However oxadiazon lost its effectiveness in the control of barnyardgrass when it was incorporated in deeper soil layers.As for the phytotoxicity of oxadiazon to rice plants, the following characteristics were observed.1) No toxic symptoms were recorded in rice plants at a concentration of oxadiazon below 0.2ppm in flooded water.2) The deeper the incorporation in soil, the less was the phyototoxicity to transplanted rice plants.3) The highest degree of phytotoxicity in rice plants was observed when the seedlings were transplanted with the entire root zone located in the oxadiazon treated layer.4) A negligible degree of phytotoxicity was observed in rice seedlings with newly developed roots coming in to contact with the oxadiazon-treated layer.5) The characteristic symptom of oxadiazon toxicity was the appearance of browning in newly developed leaves.6) Leaf browning was the external manifestation of browning of the assimilatory tissues. No adverse effect of oxadiazon was observed in other tissues.7) In general, the degree of leaf browning (browning in both leaf sheath and lamina) tended to be directly proportional to rice growth inhibition. A minimal degree of leaf sheath browning did not exert a deleterious effect on the growth of rice plants.8) Oxadiazon absorbed by the roots was readily translocated to the shoots.Based on the properties of oxadiazon as a herbicide for transplanted rice, to achieve effective weed control with minimum or no phytotoxicity to rice plants, oxadiazon should be applied in layers located at a 2-3cm depth from the soil surface. A flooded condition should be maintained after the treatment and the final concentration should not exceed 0.2ppm in the flooded water to avoid damage to rice plants.To satisfy the above conditions at the time of application of oxadiazon an effective, economic and easy application method suited to different types of soil and acceptable to a large number of farmers was developed as follows: the hebicide in the form of an emulsifiable concentrate is scattered directly over the water surface before or immediately after final puddling of the field.