Indica Rice Seedlings Research Articles

Genome-Wide Association Study of Local Thai Indica Rice Seedlings Exposed to Excessive Iron

Excess soluble iron in acidic soil is an unfavorable environment that can reduce rice production. To better understand the tolerance mechanism and identify genetic loci associated with iron toxicity (FT) tolerance in a highly diverse indica Thai rice population, a genome-wide association study (GWAS) was performed using genotyping by sequencing and six phenotypic data (leaf bronzing score (LBS), chlorophyll content, shoot height, root length, shoot biomass, and root dry weight) under both normal and FT conditions. LBS showed a high negative correlation with the ratio of chlorophyll content and shoot biomass, indicating the FT-tolerant accessions can regulate cellular homeostasis when encountering stress. Sixteen significant single nucleotide polymorphisms (SNPs) were identified by association mapping. Validation of candidate SNP using other FT-tolerant accessions revealed that SNP:2_21262165 might be associated with tolerance to FT; therefore, it could be used for SNP marker development. Among the candidate genes controlling FT tolerance, RAR1 encodes an innate immune responsive protein that links to cellular redox homeostasis via interacting with abiotic stress-responsive Hsp90. Future research may apply the knowledge obtained from this study in the molecular breeding program to develop FT-tolerant rice varieties.

Nano-selenium controlled cadmium accumulation and improved photosynthesis in indica rice cultivated in lead and cadmium combined paddy soils

Selenium nanoparticles (Se NPs) are less toxic and more biocompatible than selenite or selenate. However, studies involving spraying with Se NPs for reducing accumulation of cadmium (Cd) and lead (Pb) in rice grains have been rarely reported as yet. Herein, indica rice seedlings cultivated in Cd+Pb-spiked paddy soils (denoted as positive control) were sprayed with Se NPs sols for four times from tillering to booting stage. Compared to positive control, 50–100 μmol/L Se NPs downregulated Cd transporters-related genes such as OsLCT1, OsHMA2 and OsCCX2 in leaves and OsLCT1, OsPCR1 and OsCCX2 genes in node I at filling stage. Meanwhile, Se-binding protein 1 was distinctly elevated, involving the repression of Cd and Pb transportation to rice grains. Se NPs also differentially improved RuBP carboxylase and chlorophylls especially some key genes and proteins involving photosynthetic system. Besides, 25–50 μmol/L Se NPs diminished reactive oxygen species overproduction from NADPH oxidases whereas boosted glutathione peroxidase, reducing protein carbonylation in rice seedlings. However, the antioxidant isozymes and oxidatively modified proteins were slightly rebounded at 100 μmol/L. Se contents were noticeably elevated and confirmed to exist as selenomethionine in the rice grains following all the treatments by Se NPs. Thus, the optimal dosage of Se NPs for foliar application is 50 μmol/L, which significantly decreased Cd accumulation, improved photosynthesis and Se enrichment whereas caused no distinct reduction of Pb in the grains. Thus, an appropriate dosage of Se NPs can be conducted to decrease Cd accumulation, improve photosynthesis, and organic Se contents in rice grains.

Expression levels of the Na+/K+ transporter OsHKT2;1 and vacuolar Na+/H+ exchanger OsNHX1, Na enrichment, maintaining the photosynthetic abilities and growth performances of indica rice seedlings under salt stress.

Salt affected soil inhibits plant growth, development and productivity, especially in case of rice crop. Ion homeostasis is a candidate defense mechanism in the salt tolerant plants or halophyte species, where the salt toxic ions are stored in the vacuoles. The aim of this investigation was to determine the OsNHX1 (a vacuolar Na+/H+ exchanger) and OsHKT2;1 (Na+/K+ transporter) regulation by salt stress (200mM NaCl) in two rice cultivars, i.e. Pokkali (salt tolerant) and IR29 (salt susceptible), the accumulation of Na+ in the root and leaf tissues using CoroNa Green® staining dye and the associated physiological changes in test plants. Na+ content was largely increased in the root tissues of rice seedlings cv. Pokkali (15min after salt stress) due to the higher expression of OsHKT2;1 gene (by 2.5 folds) in the root tissues. The expression of OsNHX1 gene in the leaf tissues was evidently increased in salt stressed seedlings of Pokkali, whereas it was unchanged in salt stressed seedlings of IR29. Na+ in the root tissues of both Pokkali and IR29 was enriched, when subjected to 200mM NaCl for 12h and easily detected in the leaf tissues of salt stressed plants exposed for 24h, especially in cv. Pokkali. Moreover, the overexpression of OsNHX1 gene regulated the translocation of Na+ from root to leaf tissues, and compartmentation of Na+ into vacuoles, thereby maintaining the photosynthetic abilities in cv. Pokkali. Overall growth performance, maximum quantum yield (Fv/Fm), photon yield of PSII (ΦPSII) and net photosynthetic rate (Pn) was improved in salt stressed leaves of Pokkali than those in salt stressed IR29.

Protective Role of Mentha arvensis Aqueous Extract against Manganese Induced Toxicity by Reducing Mn Translocation and Promoting Antioxidative Defense in growing Indica Rice Seedlings

Mentha arvensis L. (Ma) leaf extract, a wide source of natural antioxidants is widely used to protect animal cells against oxidative stress. In the current study, we have studied the ameliorative effects of Ma leaf extract on Mn induced oxidative stress in rice (Oryza sativa L.) seedlings. Hydroponically grown rice seedlings treated with 1.5 mM MnCl2 showed a decline in vigour and contents of photosynthetic pigments, increased production of reactive oxygen species (O2˙‾, H2O2, and.OH), lipid peroxidation, protein thiol and carbonyl contents along with increased activity of antioxidative enzymes- superoxide dismutase (SOD), guaiacol peroxidase (GPX) and ascorbate peroxidase (APX). The activity of catalase (CAT), however, declined in the seedlings after prolonged Mn treatment of 8 days. Interestingly exogenous application of Ma leaf extract (638.4 mg ml-1) effectively restored the Mn-induced decline in seedling vigour, photosynthetic pigments, increased levels of H2O2, lipid peroxides and altered activities of antioxidative enzymes. The results indicate that exogenous application of Ma leaf extract significantly lowers the toxic effects of Mn in rice seedlings by modulating Mn translocation and reducing oxidative stress.

Paclobutrazol mitigates salt stress in indica rice seedlings by enhancing glutathione metabolism and glyoxalase system

Stress-induced methylglyoxal (MG) functions as a toxic molecule, inhibiting plant physiological processes such as photosynthesis and antioxidant defense systems. In the present study, an attempt was made to investigate the MG detoxification through glutathione metabolism in indica rice [Oryza sativa L. ssp. indica cv. Pathumthani 1] under salt stress by exogenous foliar application of paclobutrazol (PBZ). Fourteen-day-old rice seedlings were pretreated with 15 mg L−1 PBZ foliar spray. After 7 days, rice seedlings were subsequently exposed to 0 (control) or 150 mM NaCl (salt stress) for 12 days. Prolonged salt stress enhanced the production of MG molecules and the oxidation of proteins, leading to decreased activity of glyoxalase enzymes, glyoxalase I (Gly I) and glyoxalase II (Gly II). Consequently, the decreased glyoxalase activities were also associated with a decline in reduced glutathione (GSH) content and glutathione reductase (GR) activity. PBZ pretreatment of rice seedlings under salt stress significantly lowered MG production and protein oxidation, and increased the activities of both Gly I and Gly II. PBZ also increased GSH content and GR activity along with the up-regulation of glyoxalase enzymes, under salt stress. In summary, salinity induced a high level of MG and the associated oxidative damage, while PBZ application reduced the MG toxicity by up-regulating glyoxalase and glutathione defense system in rice seedlings.

In vitro plant growth promotion by ZnO nanomaterials in indica rice seedlings (Oryza sativa L.)

This research focuses on zinc oxide nanomaterials (nano-ZnO) applied to agricultural fields. Plants were exposed to nanomaterials and responded differently in tolerance to the various concentrations and types of nanomaterials. Two cultivars (SP1 and SP90) of indica rice (Oryza sativa L.) seedlings were grown at 0-1,000 mg.L-1 nano-ZnO and their morphological and physiological response was determined. Rice seedlings were harvested 5, 7, 10 and 14 days after treatments. Results demonstrated a significant increase in biomass, growth tolerance index (GTI), chlorophyll contents and antioxidant enzyme activities of the treated plant at 100 mg.L-1 nano-ZnO but these parameters decreased with increasing nano-ZnO concentration in the treated plants at 300-1,000 mg.L-1 nano-ZnO when compared to control plants (0 mg.L-1 nano-ZnO). The high accumulations of biomass, GTI and chlorophyll contents were related to production of antioxidant enzyme activities (catalase and peroxidase) in plant cells when plants were exposed to a low dose of nano-ZnO. Further investigations will determine the effect of nano-ZnO on the plant productivity.

Changes in physiological and antioxidant activity of indica rice seedlings in response to mannitol-induced osmotic stress

Changes in physiological and antioxidant activity of indica rice seedlings in response to mannitol-induced osmotic stress

Differential responses of antioxidative defense system to prolonged salinity stress in salt-tolerant and salt-sensitive Indica rice (Oryza sativa L.) seedlings

The present investigation evaluated the ability of an antioxidative defense system in terms of the tolerance against salinity-induced oxidative stress and also explored a possible relationship between the status of the components of an antioxidative defense system and the salt tolerance in Indica rice (Oryza sativa L.) genotypes. When the seedlings of a salt-sensitive cultivar was grown in sand cultures containing different NaCl concentrations (7 and 14 dS m(-1)) for 5-20 days, a substantial increase was observed in the rate of superoxide anion (O (2) (·-) ) production, elevated levels of H(2)O(2) and thiobarbituric acid reactive substances (TBARS) which indicated an enhancement in lipid peroxidation. A declination in the level of thiol clearly indicated an increase in the protein oxidation as well as a decline in the reduced forms of ascorbate (AsA) and glutathione (GSH) and the ratios of their reduced to oxidized forms occurred in the salt-sensitive seedlings. Similar treatment caused a very little alteration or no change in the levels of these components in the seedlings of salt-tolerant cultivar. The activity of antioxidative enzymes superoxide dismutase (SOD), its isoform Cu/Zn-SOD and ascorbate peroxidase (APX) increased in both the cultivars against salinity. In salt-sensitive seedlings, the activity of the various enzymes, guaiacol peroxidase (GPX), catalase (CAT), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) increased at moderate salinity treatment of 7 dS m(-1) NaCl while the activities of these enzymes declined with higher salinity level of 14 dS m(-1) NaCl. However, a consistent increase was observed in the activities of these enzymes of salt-tolerant seedlings with an increase in the duration and the level of the salinity treatment. The results suggest that a higher status of antioxidants (AsA and GSH) and a coordinated higher activity of the enzymes (SOD, CAT, GPX, APX, and GR) can serve as the major determinants in the model for depicting salt tolerance in Indica rice seedlings.

Studies on the Varietal Difference in Morphological and Physiological Charaters in Indica Rice Seedlings

Studies on the Varietal Difference in Morphological and Physiological Charaters in Indica Rice Seedlings

Studies on Varietal differences in Morphological and Physiological Characters of Indica Rice Seedlings

Studies on Varietal differences in Morphological and Physiological Characters of Indica Rice Seedlings

Modulation of proline and anthocyanin levels improves salt tolerant in indica rice seedlings

Modulation of proline and anthocyanin levels improves salt tolerant in indica rice seedlings

Effects of different Nitrogen forms and osmotic stress on water use efficiency of rice (Oryza sativa)

AbstractA hydroponic experiment with simulated water stress induced by polyethylene glycol (PEG) was conducted in greenhouse to study the effects of different nitrogen (N) forms (; and the mixture of and ) on water stress tolerance and water use efficiency (WUE and WUET) of different rice cultivars. Two rice cultivars (cv. ‘Shanyou 63’ hybrid indica and ‘Yangdao 6’ indica, China) were grown under non‐water‐ or water‐stressed condition [10% (w/v) PEG, molecular weight 6000] with different N forms for 3 weeks. Under non‐water stress, the biomass of Shanyou 63 was 50.0% and 64.3% and of Yangdao 6 was 6.9% and 87.8% higher under the supply of mixture of and than either under the sole supply of or , respectively; under water stress, the biomass of both rice cultivars decreased in all three nitrogen forms compared with non‐water stress; however, the inhibitory effect of water stress on biomass varied between and nutrition; the reduction of dry matter was significantly higher in than in nutrition. Compared with non‐water stress, under water stressed condition, WUE of both two rice cultivars significantly decreased in supply; WUE did not vary in and the mixture supply. It is concluded that (a) the resistance of water stress of rice seedlings is related to nitrogen form; (b) under water stress, could maintain a higher WUE compared with ; (c) hybrid indica rice seedlings have a higher water stress tolerance than indica rice seedlings.

Effect and Mechanism of Cold Tolerant Seed-Coating Agents on the Cold Tolerance of Early Indica Rice Seedlings

Abstract To better understand the effect and mechanism of cold tolerant seed-coating agents on the cold tolerance of rice seedlings, the physiological and biochemical effects of four cold tolerant seed-coating agents (HET, YKJ, YKZYJ, and the ABA seed coating agents) on two early indica rice varieties were studied under chilling stress. The results showed that the rice seedlings treated with cold tolerant seed-coating agents under chilling stress maintained dramatically higher root vigor, POD, CAT and SOD activities, and chlorophyll content, had lower MDA content and electrolyte leakage, and accumulated more soluble sugar and free proline, when compared with the control without the treatment, and finally showed lower plant injury rate. It was indicated that the cold tolerant seed coating agent improved the ability of rice seedlings in resisting to chilling stress. YKZYJ was ranked the first in terms of the efficiency in cold tolerance among the four cold tolerant seed-coating agents tested.

Changes in soluble and cell wall-bound peroxidase activities with growth in anoxia-treated rice ( Oryza sativa L.) coleoptiles and roots

The activity of soluble and cell wall-bound (1.0 M NaCl extractable) peroxidase in relation to growth of anoxia-grown Indica rice seedlings ( Oryza sativa L. cv. Taichung Native 1) was examined. Guaiacol and syringaldazine were used to assay for peroxidase activity. In air-grown coleoptiles, guaiacol or syringaldazine peroxidase activity initially decreased or remained constant, respectively, in the early period but then both increased as coleoptile elongation ceased. In air-grown roots, both guaiacol and syringaldazine peroxidase activities decreased slightly during the growth period. In response to anoxia, coleoptile elongation was stimulated but root growth was seriously inhibited. Anoxia induced a significant decrease in activity of cell wall-bound guaiacol and syringaldazine peroxidase while soluble peroxidase activity was not affected in coleoptiles. In contrast to coleptiles, anoxia-grown roots showed an increase in cell wall-bound guaiacol and syringaldazine peroxidase activities. When transferred to aerobic conditions, cell wall-bound guaiacol and syringaldazine peroxidase activities in anoxia-grown coleoptiles and roots recovered almost to the air-control levels. On exposure to ABA, the enhancement of coleoptile elongation and the decrease of cell wall-bound peroxidase activity in anoxia-grown coleoptiles were inhibited. These results indicate that there is a reciprocal correlation between growth and cell wall-bound peroxidase levels in etiolated rice seedlings.