Young Rice Seedlings Research Articles

Optimum seeding density and seedling age for the outstanding yield performance of Japonica rice using crop straw boards for seedling cultivation.

Crop straw boards, a novel nursery material, has proven effective for cultivating dense, young rice seedlings suitable for mechanized transplanting, thereby saving labor. However, under high-density nursery conditions, the biomass accumulation and yield formation in rice vary with different seedling ages, necessitating exploration of optimal seeding densities and seedling ages to achieve high yields. This study aims to determine the appropriate seeding densities and seedling ages using crop straw boards to maximize rice yield. Over two years, field studies were conducted using crop straw boards for rice cultivation at seeding densities of 150, 200, 250, 300, and 350 g/tray (labeled as D1, D2, D3, D4, and D5) and seedling ages of 10, 15, 20, and 25 days (labeled as A1, A2, A3, and A4).The results indicated that D4A2 significantly enhanced tiller number, dry matter accumulation, and photosynthetic capacity, resulting in a yield increase of 2.89% compared to the conventional method of D1A3. High-density and short-aged seedlings cultivated with crop straw boards can enhance rice yield by improving photosynthetic capacity and crop quality. This study emphasizes the importance of using crop straw boards for rice nursery practices, as well as selecting the appropriate seeding densities and seedling ages for optimizing rice production.

Identification and profiling of silicate-solubilizing bacteria for plant growth-promoting traits and rhizosphere competence

Excessive use of synthetic fertilizers may negatively affect overall soil health and the environment. There is a need to come up with alternative strategies to ensure competitive yields of crops and at the same time maintain soil ecological balance. The use of soil microorganisms as microbial inoculants in agriculture is considered an alternative approach to enhance crop growth. Soil is a good source of microorganisms that are capable of producing different beneficial enzymes such as silicase, phosphatase and other growth-promoting enzymes which are important in crop growth. Soil beneficial microorganisms such as silicate-solubilizing bacteria play an important role in solubilizing insoluble forms of silicates that are important in crop growth. This study was conducted to identify and profile silicate-solubilizing bacteria (SSB) in Louisiana soils and to document the colonization potential of SSB in rice (Oryza sativa) plants. Bacterial isolates were spot-inoculated on silica agar medium and incubated at 37 °C for 48 h. The clearing zone around colonies was measured and used to compute for solubilization index (SI), i.e., halo diameter (mm)/colony diameter (mm). Despite of the abundance of microorganisms found in these soils only 20 bacterial isolates are capable of solubilizing silicates; 16 were with low (SI < 2.0) and 4 with intermediate (2.00 < SI < 4.00) solubilization capacities. Further analysis also revealed that three of the isolates with intermediate silicate solubilization capacities also produced plant growth-promoting enzymes: phosphatase, 1-aminocyclopropane-1-carboxylic acid deaminase and indole-3-acetic acid enzyme. Based on the sequencing information and the phylogenetic tree, the putative SSB were identified into four genera: Aeromonas, Bacillus, Enterobacter and Pseudomonas. The fluorescent microscopy analysis revealed that the GFP-tagged SSB can colonize roots of young rice seedlings, a good indicator of SSB potential as seed treatment for scaling up its application in production field. Furthermore, information on the survival of SSB inoculates in different soil-plant systems in Louisiana and impact of management practices on SSB activity and population are needed to fully develop this bio-based approach to improve Si nutrition in soil and plants.

The Effect of Plant Densities in System of Rice Intensification (SRI) Method to Water Productivity of Paddy Field in East Sumba, East Nusa Tenggara

Principle of System of Rice Intensification (SRI) adapted to local conditions to increase productivity and environmentally friendly. The main component of SRI is single seedling per hill, young seedlings, wider spacing, intermittent irrigation, inter-cultivation, and organic fertilization. This study area of the System of Rice Intensification is in East Sumba Regency, East Nusa Tenggara, which has typical areas like soil texture, bulk density, soil water content, and rainfall. The research aimed to know the effect of plant densities in the System of Rice Intensification (SRI) method on the water productivity of paddy fields. This research initially focused on transplanting very young rice seedlings of 14 days old in two treatments of plants. The densities are broad in a square pattern (30 x 30 cm) and a Jajar Legowo pattern (20 x 10 x 40 cm). The rice was not grown in flooded paddies but moist ground, with intermittent irrigation. When SRI was concerned at a different wider spacing, it discovered the effect on water productivity for paddy fields, especially in East Sumba, East Nusa Tenggara. So that it determined the best wider spacing of the System of Rice Intensification method can apply in the area. The results show that the Jajar Legowo pattern spacing (20 x 10 x 40 cm) has a higher water productivity value of 3,4% than the spacing treatment (30 x 30 cm). Jajar Legowo was 11.9% higher than the spacing treatment (30 x 30 cm).

Orchestration of ethylene and gibberellin signals determines primary root elongation in rice.

Primary root growth in cereal crops is fundamental for early establishment of the seedling and grain yield. In young rice (Oryza sativa) seedlings, the primary root grows rapidly for 7-10 days after germination and then stops; however, the underlying mechanism determining primary root growth is unclear. Here, we report that the interplay of ethylene and gibberellin (GA) controls the orchestrated development of the primary root in young rice seedlings. Our analyses advance the knowledge that primary root growth is maintained by higher ethylene production, which lowers bioactive GA contents. Further investigations unraveled that ethylene signaling transcription factor ETHYLENE INSENSITIVE3-LIKE 1 (OsEIL1) activates the expression of the GA metabolism genes GIBBERELLIN 2-OXIDASE 1 (OsGA2ox1), OsGA2ox2, OsGA2ox3, and OsGA2ox5, thereby deactivating GA activity, inhibiting cell proliferation in the root meristem, and ultimately gradually inhibiting primary root growth. Mutation in OsGA2ox3 weakened ethylene-induced GA inactivation and reduced the ethylene sensitivity of the root. Genetic analysis revealed that OsGA2ox3 functions downstream of OsEIL1. Taken together, we identify a molecular pathway impacted by ethylene during primary root elongation in rice and provide insight into the coordination of ethylene and GA signals during root development and seedling establishment.

Self-propelled puddler for rice (Oryza sativa) crop and its evaluation

Rice is the most important food crop of India which is grown in about 43.86 million hectare. In India the production touches 112 MT milled rice used to feed 0.8 billion peoples that is 65% of the population.Rice is grown by manual transplanting of young rice seedlings in the puddled field in bending and squatting posture, which is very drudgerious operation. Prior to transplanting, puddling is done to prepare a soft seedbed for maintain water level in the field. Generally, animal drawn puddler, tractor’s cage wheel and power tiller operated rotary tiller were used for puddling operation.A self-propelled puddler developed at IIT Kharagpur for rice crop was tested in sandy loam soil of Kharagpur district in India. The average value of puddling index and the puddle depth was found to be above 78 % and 107 mm, respectively. The puddling with self-propelled puddled was found to be at par with that of rotary tiller.

Comparative Study of Rice Yield Production for Conventional Paddy Rice and Systems of Rice Intensification

Food security in Kenya is at stake due to decline in farm productivity with a combination of an ever increasing population and worsened by global warming. Improvement of agricultural productivity may not be realized soon as rice farmers currently uses traditional method of flooding rice which has been reported to yield low rice. There is need for a deliberate use of new agricultural technologies that improves productivity of rice farming. System of Rice intensification (SRI) provides an opportunity of yield improvements in rice production. This study was undertaken in Ahero Irrigation Scheme to compare yield production of conventional and SRI rice production for IR 2793-80-1 cultivar. The experiment was laid out in a randomized complete block design with three replications. SRI experiments recorded higher number of effective tillers with experiment having a spacing of 20cm by 20cm and transplanted at 8-11 days gave 321 per m² as compared to 226 effective tillers/m². Seed yield/plant was highly significant in SRI (39.61 g) as compared to a traditional paddy system (17.32 g). Transplanting rice seedling at the age of 8 to 11 days and at 20cm by 20cm spacing recorded highest seed yield/ha of 4.7 t/ha as compared to traditional flooding which recorded 2.7 t/ha. These results imply that planting young rice seedlings improves grain yield because of increase in number of tillers per square meters, plant height and better plant rooting ability.

Identification of QTLS for NH4+ and NO3- use efficiency under water stress and non-stress conditions and expression analysis of glutamine synthetase and nitrate reductase in rice (Oryza Sativa L.)

Nitrogen (N) is one of the most critical inputs and the current average nitrogen use efficiency (NUE) in the rice field is approximately 33%, poorest among cereals. Predominant form of N in aerobic soils is nitrate (NO3-) while ammonium (NH4+) exists in anaerobic soils. Development of cultivars with improved NH4+ or NO3- use efficiency by harnessing inherent significant variability for NUE can be an important approach. Considering these facts, the present study was established with one hundred twenty two and selected thirty two recombinant inbred lines (RILs) of two indica genotypes, Danteshwari × Dagad deshi under three nitrogen forms and three environments. The trend analysis of NH4+-N and NO3--N dynamics revealed that NH4+-N concentration persisted more under anaerobic condition and NO3--N concentration under aerobic conditions. Three way-ANOVA showed high level of significance for variance components (G, N, E) and their interactions effects (GXN, GXE, NXE, EXNXG) for yield and NUE and their component traits. Mean performance of genotypes depicted higher values for agronomically important traits i.e. yield and NUE under NH4+ as compared to NO3--N and N0. The phenotypic and genotypic data was statistically analyzed for QTLs identification for yield and NUE traits. A total of 58 QTLs conferring the corresponding five traits were detected under three N forms and two environments. We also investigated the different members of AMT (Ammonium transporters), NRT (Nitrate transporters), GS (Glutamine Synthetase) and GOGAT (Glutamate Synthase) genes, involved in NUE and analyzed the expression pattern of each gene using gene-specific primer in young rice seedlings. Collectively, OsGln1;1, OsGln1;2, OsGln1;3, OsGln2, OsGlt1 and OsGlt2 manifested different and reciprocal responses to nitrate and ammonium supply. The activity of enzymes NR, NiR, GS and GOGAT was significantly affected by NH4+and NO3- treatment. These results assist us to identify NH4+ and NO3- responsive cultivars which could be used for cultivation and/or used as parent’s in future breeding program to produce better nitrogen use efficiency varieties under water stress and non-stress conditions.

Group compositions: the politics of technology implemented in smallholder farming

This article investigates the connection between performance, group, and society. The argument is that group formation around particular farm operations and the details of the activities they engage in are an expression of the preferred way of technology implementation. The argument is developed using Paul Richards' notion of agriculture as performance. Two cases are presented. The first is the composition of a spraying team for weed control in smallholder oil palm production in Sumatra, connected to a global agreement on sustainable oil palm production, known as the Roundtable on Sustainable Palm Oil (RSPO). The second case is about a team of women transplanting young rice seedlings on prepared paddy fields in a village in Uttarakhand, India. A new way of rice transplanting was introduced by a local non-governmental organization, known as the System of Rice Intensification (SRI). The analysis shows that group performances provide essential information about how introduced plans, regulations and material designs are reworked and turned into meaningful and effective changes to agricultural practices. The article concludes that these activities are not merely technical adjustments but in themselves express arguments about the preferred way of organising farming, farm labor, and payments. Performing groups thus exert a form of bargaining power against development actors.Keywords: Group performance, smallholder farming, technology transfer, political acts

Identification of QTLs for nitrate and ammonium use efficiency under direct seeded condition and differential expression of genes involved in their absorption and metabolic pathway

Considering water and labor crises, area under direct seeded rice cultivation has increased. With the direct seeding during the early seedling stage the rice crop is very sensitive to water stress and nutrient deficiencies. The availability of nutrients is highly influenced by water status. Over the years, we have critically observed that under direct seeded condition at seedling stage if drought occurs the plants suffer more because of nutrient deficiency rather than water deficiency. The continued plant growth and development under changed rhizosphere depends heavily on availability of nitrogen and other nutrients (P, Fe and S) and the ability of the root system to absorb these nutrients efficiently and use in metabolism under their changed forms. Rice has evolved and adopted for efficient utilization of ammonical form of nitrogen, while nitrate from is less efficiently used at least during seedling and early vegetative phases. Most of the genotypes (except a few) we evaluated exhibited extremely low level of Nitrate transporter and Nitrate Reductase activities which are key factor and enzyme in absorption and utilization of nitrate form of nitrogen. Therefore, the identification of lines with greater nitrate use efficiency, mainly because of more efficient High Affinity Transporters, increased expression of nitrate reductase and nitrite reductase along with ammonium transporters and GS and GOGAT will certainly have key role in N efficiency of rice genotypes particularly under water stress conditions. In study 1, one hundred twenty two and selected thirty two recombinant inbred lines (RILs) of two indica genotypes, Danteshwari × Dagaddeshi were evaluated under three nitrogen forms and three environments (Irrigated, Rainfed and Terminal stage drought) along with root studies under soil filled glass rhizotrons at IGKV, Raipur, for generation of phenotypic data. The genotypic data of 162 SSR and HvSSR based markers were developed and used for identifying QTLs for agronomically complex trait i.e. NUE. The phenotypic and genotypic data was statistically analyzed for QTLs identification for yield & NUE traits using QTL Cartalographer. QTLs for nitrate and ammonical use efficiency varied significantly. A presence of QTL clusters between HvSSR 1–87(38.9cM) to HvSSR 1–89 (40.6cM) on chromosome 6, RM 449 (81.9cM) to RM5 (9.4cM) on chromosome 5, HvSSR 9–25 (14.6cM) to HvSSR 9–27 (15.5cM) on chromosome 9 and RM 434 (57.7cM) to RM 410 (64.4cM) on chromosome 5 signifies important genomic regions associated with evaluated traits under different conditions and will be useful in marker assisted breeding for NUE in rice. In study 2, we investigated the different members AMT (Ammonium transporters), NRT (Nitrate transporters), GS (Glutamine Synthetase) & GOGAT (Glutamate Synthase) genes, involved in NUE and analyzed the expression pattern of each gene using gene-specific primer in young rice seedlings by quantitative real time PCR, revealing a distinct expression pattern of these genes. Collectively, OsGln1;1, OsGln1;2, OsGln1;3, OsGln2, OsGlt1 and OsGlt2 manifested different and reciprocal responses to nitrate and ammonium supply. The relationship of these genes/enzymes and its interaction with water stress will be presented during the conference.

Chemometric analysis of N,N-dimethyl formamide-induced phytotoxicity in rice seedlings

Physiological responses of rice (Oryza sativa L. cv. XZX 45) seedlings to N,N-dimethyl formamide (DMF) were evaluated using chemometric modeling. Thirteen selected physiological parameters of the plants were monitored to evaluate the phytotoxicity from DMF exposure. The data matrix was further treated with cluster analysis and principal component analysis (PCA). Cluster analysis (CA) rendered two distinct clusters, suggesting different responses to DMF exposure between the root and shoot. PCA results suggested that relative growth rate (RGR), water use efficiency (WUE), malondialdehyde (MDA), soluble sugar (SS), proline, protein, Evan blue uptake (EBU), catalase (CAT), and peroxidase (POD) were dominant in root tissues, whereas carotenoids and total chlorophyll were most common in the shoot of DMF-treated rice seedlings. Additionally, analysis of red list index (RLI) was conducted to calculate the sensitivity index among all selected parameters in the shoots and roots at DMF EC10 and EC50 concentrations. The most sensitive parameter to DMF exposure in the shoots was proline and RGR at EC50 concentration, whereas it was EBU in root tissues. Superoxide dismutase (SOD) and CAT activities were the most sensitive parameters to DMF stress in the roots and shoots at EC10 concentration, respectively. Chemometric analysis suggested that DMF exposure caused phytotoxic stress to young rice seedlings, but plant tissues responded differently.

A Comprehensive Proteomic Survey of ABA-Induced Protein Phosphorylation in Rice (Oryza sativa L.)

abscisic acid (ABA) is a key phytohormone regulating plant development and stress response. The signal transduction of ABA largely relies on protein phosphorylation. However; little is known about the phosphorylation events occurring during ABA signaling in rice thus far. By employing a label-free; MS (Mass Spectrometry)-based phosphoproteomic approach; we identified 2271 phosphosites of young rice seedlings and their intensity dynamics in response to ABA; during which 1060 proteins were found to be differentially phosphorylated. Western-blot analysis verified the differential phosphorylation pattern of D1, SMG1 and SAPK9 as indicated by the MS result; suggesting the high reliability of our phosphoproteomic data. The DP (differentially phosphorylated) proteins are extensively involved in ABA as well as other hormone signaling pathways. It is suggested that ABA antagonistically regulates brassinosteroid (BR) signaling via inhibiting BR receptor activity. The result of this study not only expanded our knowledge of rice phosphoproteome, but also shed more light on the pattern of protein phosphorylation in ABA signaling.

Effects of silicon soil amendments and nitrogen fertilizer on apple snail (Ampullariidae) damage to rice seedlings

This study examines the potential for silicon soil amendments and nitrogen to reduce apple snail, Pomacea canaliculata Lamarck, damage to rice (Oryza sativa L.) seedlings. A rate of 75 kg/ha of nitrogen applied as (NH4)2SO4 to rice (cv IR64 and cv YTH183) seedbeds increased seedling biomass, allowing the seedlings to gain critical stem thickness and avoid snail herbivory. These seedlings remained relatively large after exposure to snails in pot experiments, mainly because of faster growth rates, but also due to lower damage from snails to >21 day-old IR64 seedlings. Silicon applied as Na2O3Si·9H20 alone (without nitrogen) reduced seedling growth compared to control seedlings. When nitrogen and silicon were applied together, the addition of silicon resulted in reduced seedling growth in YTH183 compared to seedlings treated with nitrogen alone. However, the same effect was not noted for IR64 seedlings, indicating clear variety-specific responses to seedbed inputs. Regardless of variety, silicon-treated seedlings that were transplanted to snail-infested pots at 21 days after seeding (DAS) had lower biomass than seedlings without silicon despite silicon-treated IR64 seedlings having less snail damage than untreated controls. From an experiment conducted in snail-infested ponds, we found no difference between snail damage to silicon (SiO2)-treated and control cv IR50 seedlings. Although we did not determine silicon levels in plant tissues, our results indicate that the effects of silicon soil amendments are largely insufficient to reduce the impact of apple snails to young rice seedlings (≤21 DAS).

Effects of trivalent chromium on biomass growth, water use efficiency and distribution of nutrient ele-ments in rice seedlings

This paper presents an investigation of the effects of trivalent chromium on biomass growth (RGR), water use efficiency (WUE) and distribution of nutrient elements in young rice seedlings (Oryza sativa L. cv. XZX 45) exposed to chromium nitrate (Cr(III)) hydroponically. Results indicated that phytotoxicity of Cr(III) to rice seedlings was apparent, showing an linear decrease in both RGR and WUE with increasing Cr(III) concentrations. Using the Leven-berg-Marquardt Algorithm, the effective concentrations (EC) obtained from the RGR were always smaller than these from WUE, indicating that the former was more sensitive to change of Cr(III) application than the latter. Although a dose-dependent total accumulation rate of Cr in plant materials was observed, the translocation of Cr into shoots was a restricted process during phytotransport of Cr within plant materials. Results also showed that the effect of Cr(III) application on uptake and distribution of nutrient elements in rice seedlings was variable. In conclusion, the toxic response of young rice seedlings to Cr(III) was obvious and inhibitory effects were highly dependent on the total accumulation rate of Cr in plant materials.

Light-mediated modulation of helix angle and rate of seminal root tip movement determines root morphology of young rice seedlings

abstractSeminal root growth is one of the factors to determine rice seedling establishment. Our previous reports showed light can induce Z-type wavy root and coiling root morphology in several rice (Oryza sativa L.) varieties, and the regulated Z-type and unregulated coil seminal roots were resulted by different circumnutational trajectories. Moreover, the light-induced seminal root waving was conducted by an NO-dependent signaling pathway. In order to further reveal the difference of root tip movement between straight and wavy seminal roots; here, the root tip movement trajectories of Tainung 67 variety (TNG67; presented straight root in light conditions) and Taichung Native 1 (TCN1; presented Z-type wavy root in light) were recorded and analyzed in both white light and dark (dim far-red light was applied in dark for taking time-lapse photography) conditions. The results showed the root tip movement of both rice varieties in low intensity of dim far-red light conditions were followed the circumnutation path. However, the stimuli of high intensity of white light would increase the root helix angle in TCN1 seedlings but not in TNG67. In addition, slowing down the rate of root helix was induced by white light treatment in TCN1 but not in TNG67 seedlings. In conclusion, changes of TCN1 rice seminal root morphology from straight to wavy type stimulated by light was resulted by both helix angle increasing and circumnutation rate slowing of root tip movement.

A new method for monitoring the susceptibility of the brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae), to pymetrozine by combining topical application and measurement of offspring number

Pymetrozine is a promising chemical agent for controlling the brown planthopper, Nilaparvata lugens (Stal), after resistance to some neonicotinoid insecticides developed nearly a decade ago. Susceptibility tests by assessing mortality resulting from insecticidal activity are not available for pymetrozine because its key biological action suppresses the reproductive performance of treated N. lugens females. In this study, a new simple method for monitoring the susceptibility of N. lugens to pymetrozine was developed by combining topical application and assessment of the number of offspring using young rice seedlings in a test tube. The ED50 values of the Osaka strain (collected in 1971) and Kumamoto strain (collected in 2011) of N. lugens against pymetrozine were 0.036 and 0.091 μg/g, respectively. In the future, this method will be used to monitor the susceptibility of N. lugens to pymetrozine.

Metabolite Profiling of Diverse Rice Germplasm and Identification of Conserved Metabolic Markers of Rice Roots in Response to Long-Term Mild Salinity Stress.

The sensitivity of rice to salt stress greatly depends on growth stages, organ types and cultivars. Especially, the roots of young rice seedlings are highly salt-sensitive organs that limit plant growth, even under mild soil salinity conditions. In an attempt to identify metabolic markers of rice roots responding to salt stress, metabolite profiling was performed by 1H-NMR spectroscopy in 38 rice genotypes that varied in biomass accumulation under long-term mild salinity condition. Multivariate statistical analysis showed separation of the control and salt-treated rice roots and rice genotypes with differential growth potential. By quantitative analyses of 1H-NMR data, five conserved salt-responsive metabolic markers of rice roots were identified. Sucrose, allantoin and glutamate accumulated by salt stress, whereas the levels of glutamine and alanine decreased. A positive correlation of metabolite changes with growth potential and salt tolerance of rice genotypes was observed for allantoin and glutamine. Adjustment of nitrogen metabolism in rice roots is likely to be closely related to maintain the growth potential and increase the stress tolerance of rice.

Phytotoxicity of methylene blue to rice seedlings

AB S TRACT: Methylene blue is widely used in various industrial branches. Due to insufficient treatment, its occurrence in wastewater is frequently detected, which may result in serious environment problems to aquatic organisms. Hydroponic experiments were conducted with rice seedlings (Oryza sativa L. cv. XZX 45) exposed to methylene blue to determine the effective concentration using relative growth rate and water use efficiency as response endpoints. Results showed that acute toxicity of methylene blue to rice seedlings was evident. Although a linear decrease in relative growth rate and water use efficiency was observed in rice seedlings with increasing methylene blue concentrations, relative growth rate of rice seedlings was more sensitive to change of methylene blue than water use efficiency. Using non-linear regression, EC-48 h values for 10%, 20% and 50% inhibition of the relative growth rate were estimated to be 1.54, 3.22 and 10.13 mg MB/L for rice seedlings exposed to methylene blue, respectively, while smaller EC were obtained for 96 h exposure. In conclusion, the toxic response of young rice seedlings to methylene blue is obvious and inhibitory effects are highly dependent on response endpoints and the duration of exposure period.

Biosynthetic relationship between C28-brassinosteroids and C29-brassinosteroids in rice (Oryza sativa) seedlings

A crude enzyme solution was prepared from young rice seedlings, and the metabolism of C29-brassinosteroids identified from the seedlings was examined. When 28-homoteasterone was added as a substrate, 28-homotyphasterol, teasterone, and 26-nor-28-homoteasterone were characterized as enzyme products by GC–MS/SIM analysis. With 28-homotyphasterol, 28-homoteasterone, typhasterol, 28-homocastasterone, and 26-nor-28-homotyphasterol were formed and identified as products. When 28-homocastasterone was used, castasterone and 26-nor-28-homocastasterone were identified as products. Together with the reduced biological activity of C29-brassinosteroids and their metabolites in the rice lamina inclination assay, these metabolic studies suggest a biosynthetic sequence, 28-homoteasterone↔28-homotyphasterol→28-homocastasterone for C29-brassinosteroid biosynthesis is connected to the biosynthetic sequence teasterone↔typhasterol→castasterone for C28-brassinosteroids by C-28 demethylation, i.e., in order to increase biological activity in the rice plant. Additionally, the C29-brassinosteroids seem to bio-degrade their C-26 demethylated C28-brassinosteroid analogs to reduce brassinosteroid activity in planta. In conclusion, the biosynthesis of C29-brassinosteroids is a likely alternative route to the biologically-active brassinosteroid, castasterone, in rice.

Chelator-induced phytoextraction of zinc and copper by rice seedlings

Solution culture was carried to investigate capacity of synthetic aminopolycarboxylic acids (ethylenediamine tetraacetate, N-hydroxyethylenediaminetriacetic acid, and diethylenetriamine-pentaacetate) for enhancing botanical removal and transport of heavy metals (Cu and Zn) by plants. Biodegradable organic acids (citric acid, malic acid, and oxalic acid) were also selected as alternatives to compare them with synthesized chelating agents for effectiveness. Young rice seedlings (Oryza sativa L. cv. XZX 45) were grown in nutrient solutions treated with single or combined metal solutions in presence or absence of chelating compounds. Calculation by chemical equilibrium program VISUAL MINTEQ showed that different chelating compounds had various complex potential with Cu(2+) and Zn(2+) ions, in which synthetic chelators exhibited higher complexed capability than biodegradable organic acids. All applied synthetic aminopolycarboxylic acids significantly decreased removal of metal from nutrient solution (p < 0.01), while more or less effects of organic acids supplied on biosorptive potential were observed with all treatments (p > 0.05), compared with the treatment without metal ligands. Synthetic aminopolycarboxylic acids significantly decreased metal concentrations in plant materials in all treatments (p < 0.01). However, biodegradable organic acids decreased metal concentrations in roots (p < 0.01), but enhanced them in shoots (p < 0.01). Results obtained indicated that synthetic aminopolycarboxylic acids decreased uptake of metals by rice seedlings, but translocation of metals complexed within plant materials was evident. Although exogenous biodegradable organic acids showed negligible effect on botanical removal of metals, metals complexed with organic acids was more mobile than those complexed with other chelating agents. These information collected here had important implication for the use of biodegradable metal chelators in transport of essential micronutrients in plant nutrition.

Iron Nutrition &amp;lt;i&amp;gt;vis-&amp;#224;-vis&amp;lt;/i&amp;gt; Aconitase Activity and Ferritin Accumulation in Tropical &amp;lt;i&amp;gt;Indica&amp;lt;/i&amp;gt; Rice Cultivars Differing in Grain Iron Concentration

Effect of Fe nutrition on Fe acquisition, aconitase enzyme activity and assimilation of the element in ferritin protein was studied in two indica rice cultivars viz. Sharbati and Lalat having contrasting grain Fe concentration. Young rice seedlings were grown in hydroponics with different levels of Fe. For comparison, the two cultivars were also grown in the field under natural conditions of rice culture. Iron accumulation, aconitase activity and ferritin level were higher in the high Fe containing cultivar, Sharbati than that in the low Fe containing cultivar, Lalat. While aconitase activity increased consistently with the increase in concentration of Fe in the growing medium, the same was not found to be true for accumulation of ferritin protein. The leaf ferritin level increased up to a certain level of Fe in the growing medium and declined thereafter. Levels of Fe in the growing medium giving maximum ferritin synthesis were found to be different in the two rice cultivars. In both cultivars, aconitase activity attained maximum level after 20 days of panicle emergence (heading). Pattern of Fe accumulation in the leaves in response to increasing Fe level in the nutrient solution paralleled with that of the aconitase activity indicating a positive correlation. It was concluded that accumulation of both ferritin protein and aconitase enzyme were influenced not only by the Fe level in the growing medium but also by the internal Fe concentration of the two cultivars.