Scielo RSS <![CDATA[Journal of soil science and plant nutrition]]> vol. 14 num. 2 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Effects of particle sizes of rock phosphate on immobilizing heavy metals in lead zinc mine soils</b>]]> Phosphate-induced immobilization is recognized as one of effective in situ remediation methods for heavy metal contaminated soils. Phosphate-based minerals that adsorb, chelate, or complex heavy metals in soil were greatly concerned as effective heavy metals immobilizing materials. Effects of particle sizes of rock phosphate on immobilizing heavy metals in Pb-Zn mine soils by a greenhouse experiment was conducted. Rock phosphate was added to a Pb-Zn mine soil with four different particle sizes, D97<101.43 µm (UP), D97<71.12 µm (P1), D97<36.83 ìm (P2) and D97< 4.26 µm (P3) (the diameters of 97% of the particles were less than 4.26 µm.), and 2 rates (2.5% and 5%). Lolium prenne, L. were grown in the treated soils. Compared to the control, addition of rock phosphate (RP) decreased metal contents in both roots and shoots significantly. Pb contents in shoots decreased by 19.59%-37.80% by different particle sizes at the rate of 5%, reaching lowest level at lowest particle size P3. Zn contents in shoots decreased by 13.47% -13.75 %, Cu in roots was decreased by 18.46%-67.98% and in shoots by 16.82%-32.61%, and Cd in roots decreased by 31.03%-74.23%. The results indicated that, RP can reduce the phytoavailability of Pb, Zn, Cu and Cd in soil significantly by immobilization and the effects strengthened with the decrease of particle size and increasing the rate of addition. <![CDATA[<b>How to improve yield and quality of potatoes</b>: <b>effects of two rates of urea N, urease inhibitor and Cytozyme nutritional program</b>]]> A field experiment was conducted to assess the efficiency of urea applied with urease inhibitor [N-(n-butyl) thiophosphoric triamide (nBTPT- trade-name Agrotain®), and organic compound (Cytozyme) in minimizing abiotic plant stress in a potato (Solanum tuberosum L.) in Dera Ismail Khan, Pakistan in 2010-2011. The nine treatments of control (no N or Cytozyme), urea applied at 200 and 300 kg N ha-1, Agrotain treated urea applied at 200 and 300 kg N ha-1, urea-200+Cytozyme, urea-300+Cytozyme, Agrotain treated urea-200+Cytozyme, and Agrotain treated urea-300+Cytozyme, were replicated 5 times. Potato growth, yield and quality were significantly influenced by urea applied with Agrotain and Cytozyme. Agrotain treated-urea-200 with Cytozyme resulted in maximum plant survival (91%), plant height (48 cm), plant canopy (61 cm) and the number of stems per plant (3.9 stems) compared to urea alone. Agrotain-treated urea applied at 200 and 300 kg N ha-1 increased potato yield by 46% and 42%, respectively, compared to urea alone. Cytozyme with urea @ 200 and 300 kg N ha-1 increased potato yield by 53% and 35%, respectively, comparing to potato crops receiving urea at the two N rates. Tuber yield improved by 14% when Cytozyme was applied with Agrotain-treated urea at 200 kg N ha-1. Cytozyme and urea applied with Agrotain treated urea-300+Cytozyme produced 33% of large tubers, followed by 31% of medium tubers with urea-200 and Agrotain treated urea-200+Cytozyme. Our results demonstrate that urea applied at 200 kg N ha-1 with either Agrotain or with Cytozyme have the most potential to enhance potato yield. <![CDATA[<b>Nutrients, ultrastructures, and Cd subcellular localization in the cottonseeds of three upland cotton cultivars under Cd stress</b>]]> A pot experiment was performed to study the Cd-induced alterations in seed quality at maturity in two transgenic upland cotton cultivars, ZD-90 and SGK3, and the upland cotton standard line, TM-1. The results shown that Cd content in cotton kernels increased linearly with the elevation of Cd stress levels. SGK3 accumulated more Cd than others. Protein content in the kernels was increased under Cd stress generally, but those at 600 µM Cd level were lower than that under 400 µM Cd level. The changes in oil content were inversed to that of protein content. Significant ultra-structural changes in cottonseeds were induced by Cd stress, especially at higher Cd levels, which were more obvious in TM-1, followed by ZD-90 and SGK3. Plasmolytic shrinkage, disintegration of nucleus, cell wall thickening, and eventual cell collapse and disintegration were observed in the cells of cottonseeds under Cd stress. Transmission electron microscope (TEM) observation and energy dispersive X-ray analysis (EDAX) confirmed that Cd existed in the form of rings and crystals as well as electron dense granules, occurred in the intercellular space, the cytoplasm, and the cell wall. SGK3 was a tolerance cultivar to Cd stress with greater Cd accumulation and sequestration in cottonseeds. <![CDATA[<b>Organic acids alleviate iron chlorosis in chickpea grown on two p-fertilized soils</b>]]> The objectives of this paper are to investigate the response of chickpea growing on two iron (Fe) chlorosis-inducing calcareous soils, with different Fe availability, generously supplied with phosphate (P), and to evaluate the effectiveness of a mixture of organic acids (citric, oxalic and malic) to alleviate Fe chlorosis symptoms. Application of P (+P treatment) aggravated Fe deficiency irrespective of the soil. Phosphorus-induced Fe chlorosis was alleviated when organic acids were also applied to the soil (+P+OA treatment), which was reflected in increased leaf chlorophyll concentration and decreased root ferric reductase activity in the plants growing on both soils; the effect was stronger for plants grown on the soil with the lowest Fe-available content. However, Fe chlorosis was still more severe than in the control (-P treatment) plants. The need of -P treatment plants to explore soil in order to take up nutrients is reflected in their root architecture, reduced root diameter and increased length, surface and volume relative to +P and +P+OA roots. Organic acids alleviate Fe chlorosis in function of non crystalline Fe oxides content but inhibit the root response mechanisms as a consequence of increasing Fe concentration in the soil solution. <![CDATA[<b>Urease activity and its relationships to soil physiochemical properties in a highly saline-sodic soil</b>]]> To ascertain the levels of urease activities (UA) and their relationships with soil physicochemical properties in salt-affected soils during reclamation, soil transects of a saline-sodic soil with different planting years under drip irrigation were intensively sampled. An enhanced soil UA in root zone (0-40 cm beneath drip emitter) was found as the planting years increased. In all transects, soil UA ranged from 0.38 to 8.53 µg NH4+-N released g-1 dry soil h-1 at 37 °C, and showed a large spatial variability within transect. R² of multiple regressions increased gradually with planting years, indicating that variations in UA could be better predicted after amelioration. Path analysis showed that the negative direct effects of soil pH on UA were clearly dominant, with the direct path coefficients of -0.357 ~ -0.666 (p < 0.05). Soil organic matter yielded greater positive indirect path coefficients through pH and total nitrogen. An exponential relationship was found between soil UA and pH values (p < 0.01). Our findings demonstrate that after the cultivation under drip irrigation for 3 years, soil biological activities and fertility level increased, with the decrease of soil salinity and sodicity. <![CDATA[<b>The effect and mechanism of improved efficiency of physicochemical pro-release treatment for low grade phosphate rock</b>]]> With the increasingly acute contradictions between shortage of bonanza phosphorus resources and phosphate fertilizer demands, to develop an efficient use technology for low-grade phosphate rocks (LGPR) was an inevitable choice. In this study, the physicochemical pro-release phosphate rock (PCPR) was prepared by adding modified lignin during the process of ultra-fine grinding LGPR. The relationship between phosphorus chemical composition of PCPR, molecular structure and fertilizer efficiency was explored by chemical analysis, spectral analysis and pot experiment. The results showed that after pro-release treatment of phosphate rock (PR), available phosphorus, reactive phosphorus and soluble phosphorus levels were significantly increased compared with PR. The available phosphorus content increased by 40%, the reactive phosphorus content increased more than 3.5 times, and 6 consecutive extraction soluble phosphorus accumulation increased by 24 times. The structure of the PR showed the pro-release processing would significantly increase particle fineness and specific surface area of PR , strengthen the characteristic absorption peak intensity of PO4(3-), HPO4(2-), replace the Cl-, F-, Fe²+ in the apatite and change the phase composition of PR. Pot experiment results showed corn biomass and phosphorus utilization processed by the PCPR were much higher than superphosphate (SP), diammonium phosphate(DAP), and significantly improve soil phosphorus content. The high soluble phosphorus and active phosphorus in PCPR providing the moderate continuous phosphorus supply intensity was the main reason for its high bioavailability. The combination of a static extraction and continuous extraction of reactive phosphorus and soluble phosphorus was an appropriate evaluation of physicochemical pro-release effect. <![CDATA[<b>Interaction of cyanide uptake by sorghum and wheat with nitrogen supply</b>]]> Cyanide occurs naturally in soils, arising from biological cyanogenesis and also in some cases from anthropogenic contamination. Plant utilization of cyanide at non-toxic concentrations as a supplemental source of nitrogen has been a topic of recent scientific interest and it was investigated here using sorghum (Sorghum bicolor L.) and wheat (Triticum aestivum L.). The accumulation of cyanogenic nitrogen in plant tissues was assessed under nitrogen regimes with specific combinations of cyanide, ammonium, and nitrate or each nitrogen source alone. Cyanogenic nitrogen accumulated in plant tissues when in combination with nitrate and accumulation of cyanogenic nitrogen decreased when ammonium was present. A greater increase of nitrogen in tissue from cyanide was observed in both species when cyanide was substituted for ammonium, but accumulation of cyanogenic nitrogen decreased when ammonium was present. A reciprocal nitrogen labeling experiment showed that nitrogen from nitrate and ammonium was accumulated preferentially over cyanogenic nitrogen. Differences in biomass and relative growth rate were observed in response to the treatments where plants were grown with nitrate, ammonium, or cyanide as the sole nitrogen source, but not when cyanide was present along with ammonium and nitrate. Physiological nitrogen use efficiency did not differ significantly within a species for any treatment imposed. The results suggest that cyanide as a nitrogen source can potentially support plant growth and development for up to eight weeks, but more effectively in combination with ammonium and nitrate. <![CDATA[<b>Exogenous application of glycinebetaine and potassium for improving water relations and grain yield of wheat under drought</b>]]> Compatible solutes rescue plants in the hour of intense water deficit conditions. Glycinebetaine (GB) and potassium (K) are main solutes, playing role in improving plant water potential and ultimately the crop yield. However, only a few attempts have been made so far to study their optimum dozes and interactions to ameliorate the drought stress in wheat. To explore this, GB solutions of 0, 50,100 and 150 mM concentration and K solutions of 0, 0.5, 1.0, and 1.5% concentration were sprayed at milking stage of two wheat varieties under stress (Auqab-2000; drought sensitive and Lasani-2008; drought resistant). The stress was created by withholding water up till appearance of wilting symptoms and then the solutes (alone and/or in combination) were sprayed with carboxymethyl cellulose as a sticking agent, whereas Tween-20 was used as a surfactant for foliar spray. At maturity, ten random plants from field-experiments and three in case of pot experiment were selected to estimate plant height, spike length, number of spikelets spike-1, number of grains spike-1, and grain yields. Besides, water potential, osmotic potential and turgor potential of crop were also estimated. The results indicated that the drought stress adversely affected all the above parameters. The exogenous application of GB and K to wheat significantly improved spike length, number of grain per spike and grain yields. Moreover, a significant interaction between these solutes was observed since at a given level of GB all these yield parameters were increased (p < 0.05) with K concentration. The highest values were obtained when GB and K were applied in combination at 100 mM and 1.5%, respectively. The same treatment also improved the leaf water potential, osmotic potential and turgor potential to maintain plant water potential gradient under stress. These findings lead us to conclude that application of GB and K (100 mM and 1.5%, respectively) is the best strategy to ameliorate the drought impact on wheat at milking stage with improved production. <![CDATA[<b>Compositions and properties of microbial residues formed by three single species fungi and mixed strains in cellulose-containing liquid media</b>]]> The microbial residues, due to their closely connection with humic substances (HS), aroused our considerable interest. The method of shake-flask in liquid culture was adopt to accumulate them, in which the cellulose served as the sole C source. The microbial suspensions including Trichoderma viride (Tv), Aspergillus niger (An), Penicillium (P) and mixed strains (Ms) were inoculated into the cellulose culture fluid respectively. The incubation was performed for 70 days at a constant temperature of 28 °C. The results showed that different microbial treatments had different effects on the C turnover in the cellulose fluid, among which Ms performed the most effective role in accumulating microbial residue and consuming organic C of cell metabolic product, Tv followed. As compared to cellulose, large amounts of inorganic N in the fluid could be transferred into the organic N components of residue. In the mean time, the proportion of aromatic rings could be increased at the cost of losing O-containing groups. Specifically, the degrees of condensation were enhanced by Tv and An, however their degrees of oxidation were inhibited. On the contrary, the P and Ms treatments had a significant advantage in the oxydative degradation of cellulose. Although some intermediate products (polysaccharides, phenolic compounds, carboxylic groups and syringyl units etc.) of HS could be detected in the microbial residues treated by Tv and An, their organic molecules did not still achieve the polymerization degree of real HS. <![CDATA[<b>Diagnosing of <em>rice</em> nitrogen stress based on static scanning technology and image information extraction</b>]]> At present, the identifying of rice nitrogen stress by the chemical analysis is time-consuming and laborious. Machine vision technology can be used to non-destructively and rapidly identify rice nitrogen status, but image acquisition via digital camera is vulnerable to external conditions, and the images are of poor quality. In this research static scanning technology was used to collect images of the rice's top-three leaves that were fully expand in 4 growth periods. From those images, 14 spectral and shape characteristic parameters were extracted by R, G, B mean value function and Regionprops function in MATLAB. After analyzing, the R, G, Leaf Length, LeafArea, and Leaf Perimeter were chosen as 5 universal characteristic parameters for identifying nitrogen stress in 4 growth periods. The results showed that the overall recognition accuracy of nitrogen stress were 92%, 92%, 100% and 96% respectively. Based on the result, the methodology developed in the study is capable of identifying nitrogen stress accurately in the rice. <![CDATA[<b>Soil organic carbon, dehydrogenase activity, nutrient availability and leaf nutrient content as affected by organic and inorganic source of nutrient in mango orchard soil</b>]]> Changes in soil organic carbon, dehydrogenase activity, nutrient availability and leaf nutrient concentrations in a mango orchard soil was evaluated from four years (2007-2011) field experiment on a Typic Ustocrepts soil of subtropical region in Lucknow, India. Organic (FYM, vermicompost, mulching, Azotobacter, PSM and Trichoderma harzianum) and inorganic (N, P, K) substrates were applied each year within the tree basin. It was observed that soil and leaf nutrients concentrations significantly increased in organic and inorganic amended soils as compared to control. Vermicompost, organic mulching and microbial inoculation significantly enhanced soil organic carbon content, available nutrients, dehydrogenase activity and leaf nutrient concentrations. Dehydrogenase activity was highest (1.85 ìg TPF g-1 h-1) in organically treated soils. Surface soil (0-10 cm depth) showed higher dehydrogenase activity (1.29 to 1.85 ìg TPF g-1 h-1) as compared to lower soil depths in all the treatments. <![CDATA[<b>Using a crop simulation model to select the optimal climate grid cell resolution</b>: <b>A study case in Araucanía Region</b>]]> Crop models are sensitivi by the climatic spatial scale for performing thesimulation. Several crop simulation studies use mesoescale climate database (20-50 km), where topography is neglected. We develop a method to select the optimal climate grid cell resolution (OCGR) based on winter wheat (Triticum aestivum L) yield simulations in complex topographical zones (CTZ) and flat topographical zones (FTZ) in the Araucania Region of Chile (37°35' and 39°37' S - 73°31׳ and 71.31׳ W). The OCGR was estimated from the simulated crop yield (CERES-DSSAT) using a semivariogram to compute the distance, which minimize yield differences with respect to its neighbors. Climate variables were obtained from DGF-PRECIS (25 km) downscaled to a fine resolution of 1 km through Precipitation characterization with Auto-Searched Orographic and Atmospheric (PCASOA). Climate variables were calibrated and validated from 56 in-situ meteorological stations between 1961 and 1991 and the yield was validated from field experiments. The crop simulation presented no significant differences (3.0±0.3-3.0±0.1 Mg ha-1) compared to field experiments. Increasing the resolution improves the crop simulation reducing the RSME from 0.8 to 0.32 Mg ha-1 The OCGR estimated averaged < 7 km for CTZ, whereas it was &gt; 25 km for FTZ. Our approach can be applied for similar crops and complex topographical zones. <![CDATA[<b>Soil biological and biochemical traits linked to nutritional status in grapevine</b>]]> The purpose of this work was to study vineyards of NE Italy seeking for features associated to the soil or plant compartment that could serve as proxies to infer productivity of the grape. Soils were characterized for physico-chemical properties, mineralization of organic matter by a novel patented device based on in-situ microbial degradation of buried fibers, bacterial intergenic spacer length diversity (ARISA), enzyme activities and the expression of genes involved in response to abiotic stresses. Significant differences (p<0.05) were observed among vineyards for the parameters evaluated. The groupings obtained by ARISA were coherent with those obtained by PCA of soil properties. Vineyards endowed with higher productivity had soils showing higher enzyme activities along with neutral pH, higher TOC content and appropriate C/N ratio. These soils also showed higher mineralization of organic matter determined the novel in-soil thread degradation method. Grapevines of less productive vineyards had suboptimal leaf nitrogen and sulfur contents and showed up-regulation of WRKY, SuSy, PAL and STS1 genes. Results put in evidence useful correlations with yield that can be obtained up to several months earlier than harvest time upon analyzing selected indicators. An interesting link arises unifying soil biological properties, nutritional status, molecular stress response of grapevine and its production level. <![CDATA[<b>Exogenous nitric oxide (NO) ameliorates salinity-induced oxidative stress in tomato <i>(Solanum lycopersicum)</i> plants</b>]]> Nitric oxide (NO) is involved in numerous physiological and stress responses in higher plants. Tomato is one of the most important vegetable crops in the world and previously it has been reported that salinity induced an oxidative stress affecting its redox and NO homeostasis. Using tomato plant exposed to 120 mM NaCl, it was studied whether the exogenous application of NO could ameliorate the negative effects provoked by salinity. Thus, nitric oxide provoked a significantly increase in the main antioxidative enzymes including superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR) and peroxidase (POD) activities, and also a raise of some enzymes involved in nitrogen metabolism including nitrate reductase (NR) and nitrite reductase (NiR) activities. Moreover, NO-treated plants showed a higher content in both proline and ascorbate but lower content of H2O2. These data indicate that the exogenous NO application is useful to mitigate the salinity-induced oxidative stress in tomato plants. <![CDATA[<b>Sensitivity of <i>Allium cepa</i> and <i>Vicia faba</i> towards cadmium toxicity</b>]]> Sensitivity of common onion (Allium cepa L.) and faba bean (Viciafaba L.) to cadmium (Cd) stress was investigated using genotoxicity endpoints. Simultaneously, the antioxidative stress enzymes (guaiacol peroxidise and catalase) and lipid peroxidation [malonaldehyde MDA) conten] were investigated in the plants exposed to Cd in solution. The endpoints screened for genotoxicity included chromosomal aberrations, micronuclei frequency and mitotic frequency. Additionally comet assay was performed for DNA fragmentation. Evan's blue uptake by the root meristems as a cell death parameter served as indicator of cytotoxicity. The results indicated that exposure to Cd induced dose-dependent increase in chromosomal aberrations, DNA fragmentation and micronucleus frequency in both A.cepa and V. faba. The enzymes guaiacol peroxidase (GPX) and catalase (CAT) activities increased in both the plants and were higher in V. faba. A positive correlation between the activity of GPX and CAT and MDA content was recorded at all concentrations of Cd. Regarding sensitivity, our results showed that V. faba is more sensitive plant than A. cepa towards Cd -induced toxicity. Higher genotoxicity level correlated to the increased level of oxidative stress in root tissues. This was likely to be an important cause of Vicia plant to be less tolerant than Allium. <![CDATA[<b>Using agronomic biofortification to boost zinc, selenium, and iodine concentrations of food crops grown on the loess plateau in China</b>]]> Micronutrient malnutrition among humans is typically caused by micronutrient deficiency in soils and then staple food crops grown on these soils. In this study, field trials were conducted to investigate the biofortification of micronutrients in the edible parts of winter wheat, maize, soybean, potato, canola, and cabbage. Fertilizers of Se, Zn and I were applied to soil independently or together, while Se and Zn were sprayed as solution on winter wheat in another part of the trials. Selenium, when applied to the soil in the form of sodium selenate, whether alone or combined with Zn and/or I, was effective in increasing Se to around target levels in all of the tested crops. Selenium as sodium selenite was effective as a foliar application to winter wheat, increasing it from 25 to 312 µg kg-1 in wheat grain with 60 g Se ha-1. For Zn, soil-applied zinc sulphate was only found to be effective for increasing the Zn concentration in cabbage leaf and canola seed, with 35 and 61 mg kg-1, respectively, while foliar zinc sulphate application was effective in biofortifying winter wheat, increasing grain Zn from 20 to 30 mg kg-1. While for I, soil-applied potassium iodate was only effective in increasing I concentration in cabbage leaf, and biofortification of the other crops was not possible. The enhancements of Se, Zn, and I concentration resulting from either the single or combined application of microelement fertilizers were similar. Therefore, agronomic biofortification of edible parts of various food crops with Zn, Se, and I can be an effective way to increase micronutrient concentrations, and the effectiveness depends on crop species, fertilizer forms and application methods. <![CDATA[<b>Enhancement of switchgrass <i>(Panicum virgatum</i> l.) early growth as affected by composts</b>]]> Switchgrass (Panicum virgatum L.) is a bunchgrass native to North America recently successively cultivated as an energy crop. The use of compost as soil amendment is a universal practice well known for its benefits to soil properties and plant growth. This study aimed to assess the possible benefits of compost addition on the growth parameters of four switchgrass populations, the octaploids Shelter, Shawnee and Dacotah, and the tetraploid Alamo, in pot experiments. Three growing media were prepared by mixing peat (P) with each of three different composts, a green compost (GC), a mixed compost (MC) and a coffee compost (CC), at the percentages of 5%, 10% and 20% (v/v). Results obtained showed that, with respect to the use of P only, all compost mixtures exerted positive effects on root, shoot and primary leaf lengths and on the fresh weight of the different switchgrass populations. In particular, GC/P and MC/P mixtures appeared more efficient at 5% and 10% of compost, whereas CC/P mixtures produced the best results at 10% and 20% of compost. The effects of composts were more evident for the Shawnee population and less for the Shelter one, thus indicating an involvement of the genotype in the plant response. <![CDATA[<b>Influence addition of Fine Sawdust on the Physical Properties of Expansive Soil in the Middle Nile Delta, Egypt</b>]]> This study evaluated how the fresh fine sawdust from Pinewood affects some hydro-physical properties of expansive soil which collected from the middle Nile Delta, Egypt. To fulfil this objective, a number of laboratory tests were carried on the clay loam soil samples collected from the depth of 0-30 cm. Clay loam soils were treated by sawdust at the rate of 0%, 1%, 2%, 5%, 10%, 15% and 20% on the dry weight basis. Various experimental methods were used to determine the variations in the falling-head permeability, the clay size fraction, the plasticity index, the linear shrinkage and the cracking width with different sawdust-amended soils. The results showed that the addition of sawdust decreases the clay size fraction, the plasticity index, the linear shrinkage and the cracking width, while it increases significantly the falling-head permeability, which is a sign improvement of soil hydro-physical properties. It can be concluded that sawdust had the potential to improve the hydro-physical properties of expansive soils, especially, when added into soil in between one to two percent on dry weight basis, above this percentage the improvement was much less significant and warranted by the clay content decrease. <![CDATA[<b><i>In planta</i> selection of plant growth promoting endophytic bacteria for rice <i>(Oryza sativa</i> L.)</b>]]> In this study, bacteria were isolated from the rhizosphere and inside the roots of canola (Brassica napus L.) plants grown in the field from northern Iran. Firstly, 150 strains (endophytic and rhizospheric isolates) isolated from canola were characterized for plant growth promoting (PGP) traits. Of them, one hundred isolates produced indole-3-acetic acid (IAA), whereas 17 isolates solubilized phosphate, 44 isolates produced siderophore, 34 produced 1-aminocyclopropane-1-carboxylate (ACC) deaminase and five produced hydrocyanic acid (HCN). All of the screened isolates with different growth promoting traits were separately inoculated as different mixtures on two rice cultivars under gnotobiotic conditions. A total of 22 endophytic isolates were re-isolated from two rice cultivars and characterized for Plant Growth Promoting (PGP) traits again. All 22 endophytic isolates produced IAA. Secondly, the colonization and growth promoting effects of the IAA producing endophytic strains were compared in inoculated rice plantlets as single-strain inoculants. All of the IAA producing strains were consistently more active in colonizing rice seedlings as compared with other isolates. Therefore, it seems that IAA production may be required for endophytic competence as compared to other PGP traits in rice seedlings. In addition, this study indicates that the selected bacterial isolates based on their IAA producing trait have the potential for PGP and more colonization of rice. <![CDATA[<b>Growth promotion of the rice genotypes by pgprs isolated from rice rhizosphere</b>]]> Plant growth promoting rhizobacteria (PGPRs) improve growth of the host plants in a variety of ways. For this reason five bacterial strains isolated form the rice rhizospheric soil (B 15, B 17, B 19, BN 17 and BN 30) and three standard PGPR strains (viz. Pseudomonas putida, Pseudomonasfluorescens and Azospirillum lipoferum) were tested for plant growth promotion when applied to the rice plants as seedling treatments. The experiment was conducted for two rainy seasons of the years 2010 and 2011. Rice plants inoculated with the bacterial isolates recorded an improved plant growth and higher photosynthetic capacity signified by the higher chlorophyll content. Root and shoot dry mass was also found to be increased in the inoculated plants. Besides these iron and zinc content of the treated rice plants was also found to be higher in comparison with the uninoculated control plants. Hence, it can be concluded that application of PGPR has immense potential to be used as agricultural crop inoculants as they promote plant growth as well as improve the health and yield of the plants.