Growth Of Rice Seedlings Research Articles

Toxic effect of cadmium adsorbed by different sizes of nano-hydroxyapatite on the growth of rice seedlings.

Information regarding the toxic effects of cadmium (Cd) adsorbed by nano-hydroxyapatite (NHAP-Cd) on the growth of crop plants remain limited. We investigated the mechanism of NHAP-Cd (diameters, 20 and 40nm; NHAP20-Cd and NHAP40-Cd, respectively) phytotoxicity. Rice seedlings treated with Cd and NHAP20-Cd showed more severe growth retardation compared to those treated with NHAP40-Cd, for the same Cd concentration. Transmission electron microscopy revealed NHAP in the seedlings. The nanoparticles entered the rice seedlings with no Cd2+ signals in the NHAP treatments compared to -0.47pmolcm-2s-1 of Cd2+ fluxes in the Cd treatment. The higher Cd2+ content in the leaves and mesocotyl of NHAP20-Cd-treated rice seedlings suggested that smaller NHAP-Cd can translocate easily to the aboveground parts. Further, NHAP-Cd increased oxidative stress, which was determined as catalase activity changes in this study. Thus, NHAP-Cd particles in the growth medium can be transported to rice seedlings and cause toxicity.

Ankuri Technology for Seed Germination and Seedling Emergence of Rice in Cold Environment

Rice seed germination as well as seedling emergence in cold environment is a challenge for successful rice cultivation during dry (Boro) season in northern Bangladesh Experiments were conducted in two consecutive Boro seasons in Rajshahi to develop techniques for improving germination and seedling emergence under cold conditions.. Seeds of rice var. BRRI dhan29 and BRRI dhan50 were germinated following the traditional “Zag-method” and separately in a frame covered with air tight heat insulating plastic tripal (called Ankuri- germinator). Then vapor therapy was given inside Ankuri and maintained 25-350C with high humidity. External and internal temperatures of Ankuri were recorded. Seed germination was checked at 12 h interval. In another experiment, germinated seeds of BRRI dhan29 were sown on soil in trays followed by light irrigation. One set of trays was placed in Ankuri. Another two sets of trays were placed in the field with polythene covered and uncovered. Similar experiment using non-germinated dry seed was also conducted. Vapor therapy was applied in Ankuri only in and trays were checked regularly to observe the plumule and radicle growth. The germination rate (%) of the tested varieties in Ankuri ranged from 82-96% which was 64-92% in Zag-method. High variation of germination in Zag-method was due to improper temperature and humidity during the Zag period. Seed germination was faster in Ankuri which was observed within 2.5 days. This was also 2.5 days earlier in comparison with the Zag-method. Soaking period ranged 22-24 h outside in cold water/weather. But 18 h soaking in Ankuri resulted good germination. Irrespective of varieties, the growth was 5.4 and 1.7 times more respectively for plumule and radicle in Ankuri than Zag-method. Seedling emergence was 2-3 days earlier in both dry and soaked/germinated seeds sown in trays of Ankuri than the outside polythene covered trays. Seedling emergence failed in open-trays. Average air temperature from 18:00-9:00 was cooler (150C) than 9:00-18:00 period (150C). Ankuri maintained 25-350C and high humidity which favored seed germination and seedling growth. Therefore, Ankuri could be an effective seed germination technique with faster germination, radicle and plumule growth.Bangladesh Agron. J. 2016 19(2): 115-123

Exogenous glutamate rapidly induces the expression of genes involved in metabolism and defense responses in rice roots

BackgroundGlutamate is an active amino acid. In addition to protein synthesis and metabolism, increasing evidence indicates that glutamate may also function as a signaling molecule in plants. Still, little is known about the nutritional role of glutamate and genes that are directly regulated by glutamate in rice.ResultsExogenous glutamate could serve as a nitrogen nutrient to support the growth of rice seedlings, but it was not as effective as ammonium nitrate or glutamine. In nitrogen-starved rice seedlings, glutamate was the most abundant free amino acid and feeding of glutamate rapidly and significantly increased the endogenous levels of glutamine, but not glutamate. These results indicated that glutamate was quickly metabolized and converted to the other nitrogen-containing compounds in rice. Transcriptome analysis revealed that at least 122 genes involved in metabolism, transport, signal transduction, and stress responses in the roots were rapidly induced by 2.5 mM glutamate within 30 min. Many of these genes were also up-regulated by glutamine and ammonium nitrate. Still, we were able to identify some transcription factor, kinase/phosphatase, and elicitor-responsive genes that were specifically or preferentially induced by glutamate.ConclusionsGlutamate is a functional amino acid that plays important roles in plant nutrition, metabolism, and signal transduction. The rapid and specific induction of transcription factor, kinase/phosphatase and elicitor-responsive genes suggests that glutamate may efficiently amplify its signal and interact with other signaling pathways to regulate metabolism, growth and defense responses in rice.

Nitrogenase Activity and IAA Production of Indigenous Diazotroph and Its Effect on Rice Seedling Growth

The diazotroph bacteria as ecofriendly biofer-tilizers play an important role in improving the N status and availability of paddy soil. Laboratory experiment to study nitrogenase activity and IAA production of diazotroph from rice rhizosphere and to assess its effect on the growth of rice seedling has been conducted from September to October 2014 in Agronomy and Horticulture Laboratory Faculty of Agriculture Jenderal Soedirman University, Purwokerto. The experiment was arranged as a completely randomized design and consisted of seven treatments and provided with 4 replications. The treatments were the isolates of indegenous diazotroph (T 1 = A11003, T 2 = A230041, T 3 = A24001, T 4 = A230022, T 5 = A230021, T 6 = A230042 and T 7 = without inoculation). The nitrogenase activity measured by acetylene reduction assay method and IAA production was measured by HPLC method. Plant height, leaf greeness, leaf area, total dry weight and total root length were determined on 21 days after sowing. The experimental results showed that the isolat A230021 was identified as Rhizobium sp. LM-5 and have the highest nitrogenase activity at 0.07 µM C 2 H 4 ml -1 h -1 and IAA production reached 19.01 ppm. Inoculation with strains of diazotroph enhanced chlorophyl content, total root length, and biomass production.

On Improving Seed Germination and Seedling Growth in Rice under Minimal Soil Salinity

On Improving Seed Germination and Seedling Growth in Rice under Minimal Soil Salinity

The plant growth-promoting effect of the nitrogen-fixing endophyte Pseudomonas stutzeri A15.

The use of plant growth-promoting rhizobacteria as a sustainable alternative for chemical nitrogen fertilizers has been explored for many economically important crops. For one such strain isolated from rice rhizosphere and endosphere, nitrogen-fixing Pseudomonas stutzeri A15, unequivocal evidence of the plant growth-promoting effect and the potential contribution of biological nitrogen fixation (BNF) is still lacking. In this study, we investigated the effect of P. stutzeri A15 inoculation on the growth of rice seedlings in greenhouse conditions. P. stutzeri A15 induced significant growth promotion compared to uninoculated rice seedlings. Furthermore, inoculation with strain A15 performed significantly better than chemical nitrogen fertilization, clearly pointing to the potential of this bacterium as biofertilizer. To assess the contribution of BNF to the plant growth-promoting effect, rice seedlings were also inoculated with a nitrogen fixation-deficient mutant. Our results suggest that BNF (at best) only partially contributes to the stimulation of plant growth.

Impact of TiO2 nanoparticles on lead uptake and bioaccumulation in rice (Oryza sativa L.)

Titanium dioxide nanoparticles (TiO2 NPs) are among the most widely used metal oxide nanoparticles, and their release into the environment is inevitable. The impact of this NPs release on the fate and toxicity of coexisting heavy metals is largely unknown. In this work, a series of hydroponic experiments were conducted to investigate impact of four types of TiO2 NPs, including one anatase (NAnT), one pristine rutile (NRuT) and two rutiles with hydrophilic and hydrophobic surfaces (NLRuT, NBRuT), as well as the bulk particles (BT), on the bioaccumulation of lead (Pb) by rice (Oryza sativa) seedlings. The results indicate that TiO2 NPs exposure at the levels of 10 and 1000mg/L had no significant adverse effects on the growth and development of rice seedlings. Due to its small crystallite size (252.2Å), only one type of TiO2 NPs (NAnT) entered rice seedling roots through an apoplastic route. However, NAnT particles were not translocated from roots to shoots, likely due to the obstruction effects of casparian strip in the root tissues. Both nano and bulk TiO2 reduced the bioaccumulation of Pb in rice at high TiO2 exposure levels (1000mg/L) but the extent of the reduction was TiO2-type dependent. NAnT, NRuT and NLRuT reduced the Pb concentration in rice roots by >80% and by 77–97% in shoots, likely due to the particles high sorption potential for Pb in the nutrient solution. NBRuT and BT reduced Pb levels by 45–61% in roots and 11–38% in shoots. Although NAnT was able to effectively reduce the bioaccumulation of Pb in rice tissues, this particle did accumulate in rice roots, which poses a potential risk to food safety. Accordingly, NAnT is not recommended for Pb pollution control. NRuT and NLRuT are more appropriate agents to reduce Pb contamination threats to rice plants, which in turn may mitigate health risk to humans through the food chain.

Effects of sulfate and sulfide on the life cycle of Zizania palustris in hydroponic and mesocosm experiments.

Under oxygenated conditions, sulfate is relatively non-toxic to aquatic plants. However, in water-saturated soils, which are usually anoxic, sulfate can be reduced to toxic sulfide. Although the direct effects of sulfate and sulfide on the physiology of a few plant species have been studied in some detail, their cumulative effects on a plant's life cycle through inhibition of seed germination, seedling survival, growth, and seed production have been less well studied. We investigated the effect of sulfate and sulfide on the life cycle of wild rice (Zizania palustris L.) in hydroponic solutions and in outdoor mesocosms with sediment from a wild rice lake. In hydroponic solutions, sulfate had no effect on seed germination or juvenile seedling growth and development, but sulfide greatly reduced juvenile seedling growth and development at concentrations greater than 320μg/L. In outdoor mesocosms, sulfate additions to overlying water increased sulfide production in sediments. Wild rice seedling emergence, seedling survival, biomass growth, viable seed production, and seed mass all declined with sulfate additions and hence sulfide concentrations in sediment. These declines grew steeper during the course of the 5yr of the mesocosm experiment and wild rice populations became extinct in most tanks with concentrations of 250mg SO4 /L or greater in the overlying water. Iron sulfide precipitated on the roots of wild rice plants, especially at high sulfate application rates. These precipitates, or the encroachment of reducing conditions that they indicate, may impede nutrient uptake and be partly responsible for the reduced seed production and viability.

Rice straw amendment ameliorates harmful effect of salinity and increases nitrogen availability in a saline paddy soil

Abstract High concentrations of salt (NaCl) in soils reduce plant growth and have enormous influence on nitrogen dynamics in the soil solution. However, addition of rice straw is expected to mitigate the effect of salinity on nitrogen cycling, therefore positively influencing plant growth. This study describes how rice seedling emergence and early growth in a saline paddy soil can be improved by adding rice straw to the soil and incubating the soil/straw mixtures for two months. I conducted a short-term laboratory incubation and a plant growth experiment to evaluate the benefit of rice straw addition to a saline paddy soil with respect to nitrogen availability and the associated growth response of saline tolerant (BRRI Dhan47) and saline sensitive (BRRI Dhan28) rice seedlings. A naturally saline paddy soil was collected from the coastal area of Bangladesh. The soil was then incubated with rice straw (0%, 25%, 50%, 100%, and 200% of the straw yield) for two months. After that, BRRI Dhan47 and BRRI Dhan28 rice varieties were sown in these incubated soils. Rice seedlings were harvested after 14 days of sowing. My results indicated that raw rice straw addition to saline paddy soil decreased the bio-availability of salt. Furthermore, BRRI Dhan28 responded better than the BRRI Dhan47 to increased addition of rice straw to soil. Bulk soil pH declined and nitrogen availability increased with increasing rice straw in addition to saline paddy soil. This study concluded that rice straw can be a meaningful soil amendment to decrease harmful effect of salt and increase nitrogen availability in a saline paddy soil.

イネの初期生育に関与する生理的要因の解明 : 4. 初期生育速度と穂発芽性の関係

イネの初期生育に関与する生理的要因の解明 : 4. 初期生育速度と穂発芽性の関係

イネの初期生育に関与する生理的要因の解明 : 1. 各生育段階における生長速度の品種間差異

イネの初期生育に関与する生理的要因の解明 : 1. 各生育段階における生長速度の品種間差異

Effect of methyl salicylate (MeSA), an elicitor on growth, physiology and pathology of resistant and susceptible rice varieties.

Methyl salicylate (MeSA) is a volatile organic compound synthesized from salicylic acid (SA) a plant hormone that helps to fight against plant disease. Seed treatment with MeSA, is an encouraging method to the seed industry to produce more growth and yield. The aim of our study is to find out the growth, development and disease tolerance of rice seed treated with different concentrations of MeSA. Also the seed treatments were studied to determine whether they directly influenced seedling emergence and growth in rice (Oryza sativa L) cultivars ‘IR 20, IR 50, IR 64, ASD 16, ASD 19 and ADT 46’ under greenhouse condition. MeSA seed treatments at 25, 50, 75 and 100 mg/L significantly increased seedling emergence. Effects were stronger in IR 50, and IR 64 and the effects were dose dependent, although the relationship between dose and effect was not always linear. MeSA seed treated rice plant against bacterial blight were analyzed. Bacterial blight was more effectively controlled by the seed treated with 100 mg/L than others. These results suggest that seed treatment with MeSA alters plant physiology in ways that may be useful for crop production as well as protection.

Exogenous amino acids increase antioxidant enzyme activities and tolerance of rice seedlings to cadmium stress

Cadmium (Cd) contamination has posed a serious problem for safe food production and become a potential agricultural and global environmental problem. A hydroponic experiment was carried out in this study to characterize the modulation of exogenous amino acids (glutamate, glycine, and cysteine) for antioxidant defense system against Cd‐induced toxicity in rice (Oryza sativa L.) seedlings exposed to 5.0 μmol L−1 Cd. Cd stress (5.0 μmol L−1) caused a significant inhibition of the rice seedlings growth, and the three amino acids alleviated the damaging effects of oxidation in varying degrees. Glutamate and glycine at three application rates did not influence rice plant biomass in comparison to the only Cd treatment, but 25 μmol L−1 cysteine treatment reached the control treatment level. For 25 and 100 μmol L−1 cysteine treatment, the Cd uptake in the whole rice plant was significantly higher than those in the only Cd treatment. Though all of the three amino acids played a role in decreasing lipid peroxidation, increasing catalase, superoxide dismutase activities, and reduced glutathione contents, the effect of cysteine treatment was relatively better. The main reason may be ascribed to that cysteine represents the most important conceptual fragments of glutathione, which is the main precursor of the phytochelatins. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 155–161, 2017

The growth and uptake of Ga and In of rice (Oryza sative L.) seedlings as affected by Ga and In concentrations in hydroponic cultures

Limited information is available on the effects of gallium (Ga) and indium (In) on the growth of paddy rice. The Ga and In are emerging contaminants and widely used in high-tech industries nowadays. Understanding the toxicity and accumulation of Ga and In by rice plants is important for reducing the effect on rice production and exposure risk to human by rice consumption. Therefore, this study investigates the effect of Ga and In on the growth of rice seedlings and examines the accumulation and distribution of those elements in plant tissues. Hydroponic cultures were conducted in phytotron glasshouse with controlled temperature and relative humidity conditions, and the rice seedlings were treated with different levels of Ga and In in the nutrient solutions. The growth index and the concentrations of Ga and In in roots and shoots of rice seedlings were measured after harvesting. A significant increase in growth index with increasing Ga concentrations in culture solutions (<10mgGaL−1) was observed. In addition, the uptake of N, K, Mg, Ca, Mn by rice plants was also enhanced by Ga. However, the growth inhibition were observed while the In concentrations higher than 0.08mgL−1, and the nutrients accumulated in rice plants were also significant decreased after In treatments. Based on the dose-response curve, we observed that the EC10 (effective concentration resulting in 10% growth inhibition) value for In treatment was 0.17mgL−1. The results of plant analysis indicated that the roots were the dominant sink of Ga and In in rice seedlings, and it was also found that the capability of translocation of Ga from roots to shoots were higher than In. In addition, it was also found that the PT10 (threshold concentration of phytotoxicity resulting in 10% growth retardation) values based on shoot height and total biomass for In were 15.4 and 10.6μgplant−1, respectively. The beneficial effects on the plant growth of rice seedlings were found by the addition of Ga in culture solutions. In contrast, the In treatments led to growth inhibition of rice seedlings. There were differences in the phytotoxicity, uptake, and translocation of the two emerging contaminants in rice seedlings.

Interactive effects of cadmium and Microcystis aeruginosa (cyanobacterium) on the growth, antioxidative responses and accumulation of cadmium and microcystins in rice seedlings.

Cadmium pollution and harmful cyanobacterial blooms are two prominent environmental problems. The interactive effects of cadmium(II) and harmful cyanobacteria on rice seedlings remain unknown. In order to elucidate this issue, the interactive effects of cadmium(II) and Microcystis aeruginosa FACHB905 on the growth and antioxidant responses of rice seedling were investigated in this study, as well as the accumulation of cadmium(II) and microcystins. The results showed that the growth of rice seedlings was inhibited by cadmium(II) stress but promoted by inoculation of M. aeruginosa FACHB905. cadmium(II) stress induced oxidative damage on rice seedlings. Inoculation of M. aeruginosa FACHB905 alleviated the toxicity of cadmium(II) on rice seedlings. The accumulation of cadmium(II) in rice seedlings was decreased by M. aeruginosa FACHB905, but the translocation of cadmium(II) from root to shoot was increased by this cyanobacterium. The accumulation of microcystins in rice seedlings was decreased by cadmium(II). Results presented in this study indicated that cadmium(II) and M. aeruginosa had antagonistic toxicity on rice seedlings. The findings of this study throw new light on evaluation of ecological- and public health-risks for the co-contamination of cadmium(II) and harmful cyanobacteria.

Variation of DNA methylation patterns associated with gene expression in rice (Oryza sativa) exposed to cadmium.

We report genome-wide single-base resolution maps of methylated cytosines and transcriptome change in Cd-exposed rice. Widespread differences were identified in CG and non-CG methylation marks between Cd-exposed and Cd-free rice genomes. There are 2320 non-redundant differentially methylated regions detected in the genome. RNA sequencing revealed 2092 DNA methylation-modified genes differentially expressed under Cd exposure. More genes were found hypermethylated than those hypomethylated in CG, CHH and CHG (where H is A, C or T) contexts in upstream, gene body and downstream regions. Many of the genes were involved in stress response, metal transport and transcription factors. Most of the DNA methylation-modified genes were transcriptionally altered under Cd stress. A subset of loss of function mutants defective in DNA methylation and histone modification activities was used to identify transcript abundance of selected genes. Compared with wide type, mutation of MET1 and DRM2 resulted in general lower transcript levels of the genes under Cd stress. Transcripts of OsIRO2, OsPR1b and Os09g02214 in drm2 were significantly reduced. A commonly used DNA methylation inhibitor 5-azacytidine was employed to investigate whether DNA demethylation affected physiological consequences. 5-azacytidine provision decreased general DNA methylation levels of selected genes, but promoted growth of rice seedlings and Cd accumulation in rice plant.

Seed Priming with Beta-Amino Butyric Acid Improves Abiotic Stress Tolerance in Rice Seedlings

We studied the influence of seed priming with beta-amino butyric acid (BABA) on the growth, physiological and biochemical parameters of seedlings with varied abiotic stress tolerance, which were raised and grown under unstressed and stressed (NaCl/PEG-6000) conditions. Under stressed conditions, the growth of rice seedlings was less when compared to control plants. After BABA priming, the seedling growth increased both under unstressed and stressed conditions as compared to the respective controls. BABA priming of rice seeds caused increase in the photosynthetic pigment content of the leaves, modified the chlorophyll a fluorescence related parameters and also enhanced the photosystem activities of seedlings when compared to their respective non-primed controls. BABA priming also caused increased mitochondrial activities of the rice seedlings. Moreover, BABA priming significantly reduced malondialdehyde content in the seedlings and also resulted in accumulation of proline especially in the NaCl tolerant variety Vyttila 6. BABA seed priming also enhanced the activity of nitrate reductase enzyme and activities of antioxidant enzymes like guaiacol peroxidase and superoxide dismutase. The presence of BABA was detected by high performance thin layer chromatography analysis in the rice seeds whereas in the seedlings it was not detected. Thus, it can be inferred that the seed priming effect of BABA mainly occurred within the seeds, which was further carried to the seedlings. It is concluded that BABA priming of seeds improved the drought and salinity stress tolerance of all the three rice varieties and it was significantly evident in the drought tolerant variety Vaisakh and NaCl tolerant variety Vyttila 6, when compared to the stress sensitive variety Neeraja.

Effect of salinity and soil temperature on the growth and physiology of drip-irrigated rice seedlings

ABSTRACTDrip irrigation offers potential for rice (Oryza sativa L.) production in regions where water resources are limited. However, farmers in China’s Xinjiang Province report that drip-irrigated rice seedlings sometimes suffer salt damage. The objective of this study was to learn more about the effects of soil salinity and soil temperature on the growth of drip-irrigated rice seedlings. The study consisted of a two-factor design with two soil salinity treatments (0 and 1.8 g kg−1 NaCl) and three soil temperature treatments (18°C, 28°C and 36°C). The results showed that shoot biomass, root biomass and root vigor were greatest when seedlings were grown with no salt stress (0 g kg−1 NaCl) at 28°C. Moderate salt stress (1.8 g kg−1 NaCl) combined with high temperature (36°C) significantly reduced root and shoot biomass by 39–53%. Moderate salt stress and high temperature also increased root proline concentration by 77%, root malonyldialdehyde concentration by 60% and seedling mortality by 60%. Shoot and root Na+ concentrations, shoot and root Na+ uptake and the Na+ distribution ratio in shoots were all the greatest when moderate salt stress was combined with high temperature. In conclusion, high soil temperature aggravates salt damage to drip-irrigated rice seedlings. Therefore, soil salinity should be considered before adopting drip-irrigation for rice production.

The effect of periphyton on seed germination and seedling growth of rice (Oryza sativa) in paddy area

Periphyton is widely distributed in paddy fields and its interactions with paddy soil and rice growth have been reported rarely. In this study, model paddy ecosystems with different additional soil substrates were simulated under controlled conditions to investigate the effects of periphyton on rice seed germination and seedling growth. Results show that the selected soil substrates had significant effects on the metabolic activities and growth of periphyton in paddy fields. The addition of straw to soil enhances but the addition of biochar leads to attenuation of periphyton growth. The presence of periphyton in the paddy system, especially with straw in soil greatly increased the germination index of rice seed (by maximally 21%). However, the biochar treatment in the presence of periphyton was detrimental for the seed vitality with a decrease of 30%. As a result, the periphyton cover on paddy soil surface significantly inhibited the growth of rice seedling, including rice height, leaf width and biomass. To summarize, this study indicates that the presence of periphyton during seed germination period was detrimental for rice growth, but could be used to control the weed growth. Thus, this study provided insight into understanding the periphyton-plant relationships with different soil-substrates and also new approaches to controlling weeds in paddy fields by regulating the growth of periphyton.

English

In this study, the effects of Ligusticum chuanxiong extract as herbicide safeners were determined on glutathione-S-transferase (GST) activity of rice crop. Two main extract compounds, Z-ligustilide and senkyunolide A, were identified by high performance liquid chromatography and liquid chromatography-mass spectrometry. In both bioassays conducted in agar and soil, the whole L. chuanxiong extract, as well as two active components individually were effective in safening the growth of rice seedlings against S-metolachlor toxicity. Z-Ligustilide was a better safener than senkyunolide A, and both compounds were more protective of shoots than roots. After herbicide-inhibited rice seedlings were treated with Z-ligustilide, GST activity significantly increased, suggesting the safening effect of this L. chuanxiong extract component involves GST. © 2016 Friends Science Publishers