Different Organs Of Rice Research Articles

Effects of Biochar on the Cd Uptake by Rice and the Cd Fractions in Paddy Soil: A 3-Year Field Experiment

Biochar is a potential amendment for the remediation of Cd-contaminated soils. Although the immobilization effect of biochar on soil Cd has been studied under indoor laboratory conditions, the effect of biochar on rice Cd uptake and soil Cd fractions under field conditions is still poorly understood. Here, the Cd content of the different organs of rice and the Cd fractions in soil were characterized for three years after the application of different amounts of biochar (0, 7.5, 15, 30 t ha−1, and 3 t ha−1 year−1). The Cd content of brown rice, husk, leaf, stem and sheath, and root under biochar treatment could be maximally reduced by up to 26.25%, 20.16%, 20.74%, 33.2%, and 26.89%, respectively. Biochar altered the Cd fractions in soil, including the decrease in exchangeable Cd content and the increase in Fe-Mn oxide bound Cd and organic bound Cd. The concentration factor of Cd uptake by rice was reduced by 32% under biochar application, while biochar had little influence on the transfer factor and distribution factor. The immobilization effect of biochar on soil Cd lasted for at least three years, but the trend of Cd immobilization efficiency over time for different amounts of biochar treatment was different. The Risk Assessment Code (RAC) of Cd in soil with biochar amendment could be reduced to a medium risk level from a high risk level. Redundancy analysis (RDA) revealed that changes in soil pH and Fe-Mn oxide bound Cd content caused by biochar application contributed most to the reduction in the Cd content of rice organs. These findings would enhance our understanding of the immobilization effect of biochar on Cd in paddy soil under field conditions.

Spatial ionomics provides new insights into the accumulation and transport of mineral ions in rice (Oryza sativa L.) under Cadmium stress

The distribution of various elements in different organs is spatially specific, and the distribution of elements in different organs of rice under Cadmium (Cd) stress and nutrient deficiency conditions is unknown, these limit the creation of ideal crops. In this study, spatially-specific ionomics study was applied to the spatial distribution of ions in different organs of 14 different varieties of hybrid rice seedlings under Cd stress. Under Cd stress, magnesium (Mg), manganese (Mn), zinc (Zn), copper (Cu), and iron (Fe) were found to accumulate mainly in the nodes, while Ca accumulated mainly in the mature leaves, and K mainly in the leaf sheaths and new leaves. Under Cd stress, the contents of Mg and Mn in all organs and Mg, Mn, Zn, Ca, Cu, and Fe in nodes decreased, but the accumulation of Fe in roots increased. In all organs, the concentrations of calcium (Ca), Mg, Mn, and Fe were almost positively correlated. Moreover, the ion transfer factors of Mg/Mn, Mg/Cu, and Zn/potassium (K) all showed positive correlations, indicating that these elements had similar chemical properties or biological functions. The accumulation of Cd in different organs of 4 varieties under Cd stress and K/Mn/Ca/Mg deficiency treatments was studied. Under Mg deficiency stress, the Cd concentration increased significantly. Under Ca deficiency stress, Cd transport was reduced. In conclusion, spatial ionomics was used to investigate the transport and accumulation of elements in different organs of O. sativa L., and these results provided theoretical support for the creation and production of ideal crops under Cd stress.

<sup>15</sup>N Tracer-based Analysis on Nitrogen Utilization Laws of Rice Under Different Irrigation Modes

In order to promote the efficient and coordinated utilization of water and nitrogen in rice, the  15 N missing technology experiment was adopted to study the effects of nitrogen application rate (N 0 , N 160 , N 200 , N 240 ) and irrigation mode (Wet-dry alternation, conventional irrigation) on nitrogen absorption, transport, residue, loss and nitrogen utilization of super rice. The results showed that with the increase of nitrogen application rate, the accumulation of fertilizer nitrogen and total nitrogen in rice plants at different growth stages, and the accumulation of nitrogen in various organs at mature stage increased significantly, and the accumulation of nitrogen per panicle at mature stage was the highest, reaching 67.20%~69.02%. The transport amount of nitrogen from different sources in different vegetative organs of rice plants increased with the increase of nitrogen application rate, and the comparison of nitrogen transport amount in organs was as follows: leaf > stem > root; After full heading, the accumulation of nitrogen from different sources and its contribution rate to grain nitrogen per spike increased with the increase of nitrogen application rate, but with the increase of nitrogen application rate, the residual amount of soil fertilizer nitrogen increased significantly, the residual rate showed a downward trend, and the nitrogen loss rate increased significantly. Dry-wet alternate irrigation treatment can increase nitrogen accumulation in different organs of rice in different periods, improve nitrogen use efficiency and rice yield to a certain extent. This study summarized the laws of nitrogen absorption, utilization, residue and loss of rice under different irrigation conditions and different nitrogen application conditions, which provided a theoretical basis for efficient cultivation of rice.

Dynamics of gene expression associated with arsenic uptake and transport in rice during the whole growth period

BackgroundGenes associated with arsenite uptake and transport in rice plants (i.e., OsLsi1, OsLsi2, OsLsi3, OsLsi6 and OsABCC1) have been identified to date. However, their expression over time during the whole growth period of rice under arsenite stress conditions is still poorly understood. In this study, the dynamics of gene expression associated with arsenite transport and arsenic concentrations in different organs of rice were investigated to determine the critical period(s) of arsenite uptake and translocation regulated by gene expression during the whole growth period.ResultsThe relative expression of OsLsi2 and OsLsi1 in the roots was upregulated and reached its highest value (2-∆∆Ct = 4.04 and 1.19, respectively) at the jointing stage (9 weeks after transplantation), in which the arsenic concentration in roots also was the highest at 144 mg/kg. A range from 45.1 to 61.2% of total arsenic accumulated in the roots during seedling to heading stages (3–16 weeks), which was mainly associated with the relatively high expression of OsABCC1 (1.50–7.68), resulting in arsenic located in the vacuoles of roots. Subsequently, the As translocation factor from root to shoot increased over time from heading to milky ripe (16–20 weeks), and 74.3% of the arsenic accumulated in shoots at the milk stage. Such an increase in arsenic accumulation in shoots was likely related to the findings that (i) OsABCC1 expression in roots was suppressed to 0.14–0.75 in 18–20 weeks; (ii) OsLsi3 and OsABCC1 expression in nodes I, II, and III was upregulated to 4.01–25.8 and 1.59–2.36, respectively, in 16–20 weeks; and (iii) OsLsi6 and OsABCC1 expression in leaves and husks was significantly upregulated to 2.03–5.26 at 18 weeks.ConclusionsThe jointing stage is the key period for the expression of arsenite-transporting genes in roots, and the heading to milky ripe stages are the key period for the expression of arsenite-transporting genes in shoots, both of which should be considered for regulation during safe rice production in arsenic-contaminated paddy soil.Graphical abstract

Effect of CO2 Doubling and Different Plant Growth Stages on Rice Carbon, Nitrogen, and Phosphorus and Their Stoichiometric Ratios

The variation characteristics of ecological stoichiometric ratios can reflect the nature of plant adaptation to environmental changes. The C, N, and P contetns, and their stoichiometric ratios in different organs of rice were studied using a CO2 continuous labeling system, by simulating the increase of atmospheric CO2 concentration (800×10-6). The results showed that CO2 doubling promoted the growth of rice organs and increased the root/shoot ratio. CO2 doubling reduced the shoot TN content in different growth periods, increased the C/N ratio in the rice root, shoot, and grain, decreased the N use efficiency, and improved the P use efficiency. Multiple comparison and Venn diagram analyses showed that CO2 concentration only has a significant impact on the TN content in the rice shoot; it contributed little to the variation in rice nutrient content and their stoichiometric ratios, indicating that CO2 doubling had no effect on these. Under the condition of elevated atmospheric CO2 concentrations, the C, N, and P contents and their stoichiometirc ratios, in rice organs had good homeostasis, and the stoichiometric change during growth periods was consistent with "the Growth Rate Theory". In farmland management, appropriate nitrogen fertilizers can alleviate the nutrient balance pressure caused by the increase in CO2 concentration.

Effect of Modified Bentonite on Cd Accumulation in Different Organs and Growth of Rice under Cadmium Stress

Modified bentonite(MB) was added in culture solution with different concentration of Cd to inhibit migration of Cd from culture solution to rice seeding. Biomass of rice, Cd concentration of culture solution over time and Cd concentration of different organs of rice were determined. The result showed that MB could improve growth of rice in the culture solution with no Cd was added. MB could decrease Cd concentration of culture solution for its good adsorption on Cd, but it did not completely immobilize Cd in culture solution. Adding MB in culture solution with Cd only alleviate poison of Cd on rice.

Effect of Various Intensities of Drought Stress on δ<sup>13</sup>C Variation among Plant Organs in Rice: Comparison of Two Cultivars

The δ13C value is widely used to assess the effects of drought on water status in plants. However, there is little information regarding the δ13C signature in different organs of rice. We conducted a field study to examine whether the δ13C among different plant parts would be affected by the intensities of drought, and to evaluate genotypic variation in δ13C fluctuation among plant parts affected by drought intensities. Two cultivars, “Nipponbare” (Oryzasativa ssp. japonica) and “Kasalath” (O. sativa ssp. indica), were grown in the field with a line-source sprinkler system. The δ13C values of panicles, flag leaves, straws, culms, and roots were measured from plant samples. The δ13C value increased as drought stress increased, especially in the panicles and roots. “Nipponbare” showed higher values of δ13C than “Kasalath” under the well-watered and mild drought stress conditions, but there was no significant difference between the genotypes in the δ13C value under the severe drought stress condition. The variation in δ13C value among different plant parts was also increased with increasing drought stress. In contrast, these variations were small under well-watered conditions. Furthermore, there was much greater variation in the δ13C value among different plant parts in “Kasalath” than in “Nipponbare” when the plants were grown under drought stress conditions. A significant negative relationship was observed between the δ13C value of panicles and shoot dry matter production, suggesting that the δ13C value of panicles may be the best indicator of plant water status in rice.

Fine mapping of qHUS6.1, a quantitative trait locus for silicon content in rice (Oryza sativa L.)

Silicon is essential for optimal growth of rice (Oryza sativa L.). This study was conducted to fine map qHUS6.1, a quantitative trait locus (QTL) for rice hull silicon content previously located in the interval RM510-RM19417 on the short arm of chromosome 6, and to analyze the effect of this QTL on the silicon content in different organs of rice. Selfed progenies of a residual heterozygous line of rice were detected using 13 microsatellite markers in the vicinity of qHUS6.1. Three plants with overlapping heterozygous segments were selected. Three sets of near isogenic lines (NILs) were developed from the selfed progenies of the 3 plants. They were grown in a paddy field and the silicon contents of the hull, flag leaf, and stem were measured at maturity. Based on analyses of the phenotypic distribution and variance among different genotypic groups in the same NIL set, a significant genotypic effect was shown in the NIL set that was heterogenous in the interval RM19410-RM5815, whereas a significant effect was not found in the remaining 2 NIL sets that were heterogenous in either of the intervals RM4923-RM19410 or RM19417-RM204. On comparison among the physical positions of the 3 heterogenous segments, qHUS6.1 was delimited to a 64.2-kb region flanked by RM19410 and RM19417 that contains nine annotated genes according to the genome sequence of Nipponbare. This QTL showed strong effects on all of the three traits tested, and the enhancing alleles were always derived from the paternal line Milyang 46. The present study will facilitate the cloning of qHUS6.1 and the exploration of new genetic resources for QTL fine mapping.

Effects of Irrigation Regimes during Grain Filling on Grain Quality and the Concentration and Distribution of Cadmium in Different Organs of Rice

The objective of this study was to investigate whether the grain quality could be improved and the proportion of cad-mium(Cd)be reduced in grains through a proper irrigation regime when rice was planted in Cd-contaminated soil.Two rice cul-tivars of Yangjing 9538(japonica)and Yangdao 6(indica)were pot-grown.150 mg kg-1 Cd was added into pots before seedling transplanting(Cd treatment),and no Cd addition was taken as control(CK).Three irrigation regimes,well-watered(WW),mod-erate dry-wet alternate irrigation(MD,soil was re-watered when soil water potential reached at-20 kPa),and severe dry-wet al-ternate irrigation(SD,soil was re-watered when soil water potential reached at-40 kPa),were imposed from 7 d after heading to maturity.The results showed that under the same Cd concentration in soil and when compared to WW,MD significantly increased,whereas SD significantly reduced,seed-setting rate,1 000-grain weight,grain yield,brown rice rate,milled rice rate,and head rice rate.MD markedly reduced,while SD increased,chalkiness.There were no significant differences in the seed-setting rate,1 000-grain weight,and each index of rice quality between the Cd treatment and the control.Under the Cd treatment and com-pared to WW,MD,and SD significantly increased the concentration and proportion of Cd in roots,while significantly reduced Cd concentration in stems and leaves and reduced Cd proportion in grains.Cd concentrations in grains and milled rice were signifi-cantly higher under SD than under WW,and exhibited no significant difference between MD and WW.SD showed lower propor-tion of Cd in milled rice,when compared to MD or WW.The two cultivars behaved the same.The results indicate that a moderate dry-wet alternate irrigation during grain filling could increase grain yield,improve milling and appearance quality and not in-crease Cd concentration or even reduce Cd proportion in grains.Reasons for variations in grain yield,quality,and the concentra-tion and proportion of Cd under different irrigation regimes were analyzed from the aspects of root activity,photosynthetic cha-racters,and Cd translocation.

Overexpression of OsERF1, a novel rice ERF gene, up-regulates ethylene-responsive genes expression besides affects growth and development in Arabidopsis

Ethylene-responsive factors (ERFs), composing the largest group of AP2/EREBP transcription factors, are involved in diverse functions and some of them have been identified in plants. However, even in model plants Arabidopsis and rice, most of the genes in this group are functionally unknown yet. Especially in rice, ERF genes involved in ethylene response have not been reported previously. Here, we report a novel member of ERF group in rice, OsERF1 (Ethylene Response Factor gene in Oryza sativa). OsERF1 expressed consistently in different organs of rice and could be up-regulated by ethylene, a plant hormone associated with stress response. Overexpression of OsERF1 in Arabidopsis up-regulated the expression of two known ethylene-responsive genes, PDF1.2 and b-chitinase, and also significantly affected the growth and development of transgenic Arabidopsis. These results suggest the involvement of OsERF1 in ethylene response.

Effects of Irrigation Patterns during Grain Filling on Grain Quality and Concentration and Distribution of Cadmium in Different Organs of Rice

The objective of this study was to investigate whether grain quality could be improved and the proportion of cadmium (Cd) be reduced in grains through a proper irrigation management when rice ( Oryza sativa L.) was planted in Cd-contaminated soil. Two rice cultivars, Yangjing 9538 ( japonica) and Yangdao 6 ( indica), were pot-grown. A total of 150 mg kg −1 Cd was added into pots before seedling transplantation (Cd treatment), and Cd-free treatment was used as the control. Three irrigation patterns, well-watered (WW), moderate dry-wet alternate irrigation (MD, soil was re-watered when soil water potential reached −20 kPa), and severe dry-wet alternate irrigation (SD, soil was re-watered when soil water potential reached at −40 kPa), were carried out from 7 d after heading to maturity. Under the same Cd concentration in soil and compared to WW, MD significantly increased, but SD significantly reduced seed-setting rate, 1000-grain weight, grain yield, brown rice rate, milled rice rate, and head rice rate. Moderate dry-wet alternate irrigation markedly reduced, whereas SD increased chalkiness. There were no significant differences in seed-setting rate, 1000-grain weight, and quality traits of rice between the Cd treatment and the control. Under the Cd treatment and compared to WW, MD and SD significantly increased the concentration and proportion of Cd in roots, but significantly reduced Cd concentration in stems and leaves and reduced Cd proportion in grains. Cadmium concentrations in grains and milled rice were significantly higher under SD than under WW, and exhibited no significant difference between MD and WW. Severe dry-wet alternate irrigation resulted in lower proportion of Cd in milled rice compared to MD or WW. The results from this study indicate that moderate dry-wet alternate irrigation during grain filling increases grain yield and improves milling and appearance quality, but does not increase Cd concentration or even reduce Cd proportion in grains. The reasons for variations in grain yield, quality, and the concentration and proportion of Cd under different irrigation patterns were analyzed in terms of root activity, photosynthetic characters, and Cd translocation.

イネ光合成器官のプロテオーム解析：光合成・一次代謝関連酵素の比較

イネ光合成器官のプロテオーム解析：光合成・一次代謝関連酵素の比較

Genetic Dissection of Silicon Content in Different Organs of Rice

Quantitative trait loci (QTLs) analysis for Si content in rice (Oryza sativa L.) was performed to study the inheritance of Si content in rice. A recombinant inbred line (RIL) population of 244 lines derived from the indica rice cross ‘Zhenshan 97B’ (ZS97B)/‘Milyang 46’ (MY46) were grown in 2003 with two replications. Silicon content in the hull (HUS), flag leaf (FLS), and stem (STS) were measured. On the basis of a linkage map consisting of 207 DNA marker loci, a total of 10 QTLs showing significant additive effects and 14 digenic interactions having significant additive‐by‐additive (AA) epistatic effects were detected. The number of QTLs and AA interactions for individual traits were four and four for HUS, four and four for FLS, and two and six for STS, respectively. General contributions to the phenotype variance due to additive effects and AA effects were 29.3 and 18.6% for HUS, 14.8 and 13.6% for FLS, and 8.6 and 28.6% for STS, respectively. This indicates that gene actions at both the one‐ and two‐locus levels play an important role to genetically control Si content in rice. In addition, it was shown that the detection of QTLs at the one‐locus level, as well as magnitude and direction of the additive effect, might be influenced greatly by digenic interactions involving loci linked to the given QTL. By comparing these results with other reports, genetic association between QTLs for Si content and QTLs for yield component traits and lodging‐tolerance related traits were evident.

Characterization of a cDNA Encoding a Novel Subunit for Cytochrome c Oxidase (COX6b) from Rice.

To date, there have been only a limited number of reports about the nuclear-encoded subunit for cytochrome c oxidase (COX) in the mitochondria of higher plants. In the present study, we characterized a cDNA encoding a novel subunit of COX (COX6b), which had not previously been reported in plants. It was found that the rice COX6b gene encodes 169 amino acids with a calculated molecular mass of 19 kDa. The deduced amino acid sequence of rice COX6b is longer than those of vertebrate and yeast COX6b subunits. Genomic Southern hybridization suggested that the rice COX6b subunit is encoded by at least two copies of COX6b genes. Northern hybridization showed that one of the genes (COX6b-1) is constitutively transcribed in different organs of rice. However, the steady-state mRNA levels slightly varied among organs.