Soil Pot Experiments Research Articles

EDTA Shuttle Effect vs. Lignosulfonate Direct Effect Providing Zn to Navy Bean Plants (Phaseolus vulgaris L 'Negro Polo') in a Calcareous Soil.

Zn-Lignosulfonates (LS) fertilizers are used as an eco-friendly alternative to chelate formulations. The mechanisms of Zn release in the rhizosphere by both types of products are compared. The ability to provide Zn to Phaseolus vulgaris L of non-modified and chemically modified ZnLS and ZnEDTA is compared in a hydroponic assay. Stable isotope 67Zn was used to study Zn source (fertilizer, ZnFer, or native, ZnNat) uptake and distribution in plants in two soil pot experiments. ZnEDTA was the best treatment to provide both ZnFer and ZnNat to navy bean plants. A shuttle effect mechanism and an isotopic exchange may occur. ZnLS from eucalyptus (ZnLSE) provides more Zn to the plant than LS from spruce. Chemical modifications of ZnLSE does not improve its efficiency. A double dose of ZnLSE provides similar ZnFer in leaves and similar soluble ZnFer content in soil than ZnEDTA. A model for the Zn fertilizers behavior in the soil and plant system is presented, showing the shuttle effect for the synthetic chelate and the direct delivery in the rhizosphere for the ZnLS complex.

Aging and Substrate Type Effects on Iodide and Iodate Accumulation by Barley (Hordeum vulgare L.)

The mechanism of iodine uptake by plants from soil is the interest of many studies, though the information about the uptake mechanism and iodine mobility in soil is still insufficient. The uptake of the most common naturally occurring iodine species in soil—iodide and iodate by barley (Hordeum vulgare L.) from iodine-spiked soil and agar cultivation media was evaluated in our study based on laboratory pot and petri dish experiments. Soil pot experiments were conducted in two stages: after iodine spiking and after a 3-month aging period taking account on the processes that can influence iodine bioavailability. Our results indicate that iodine bioavailability does depend on the form of iodine present in the growth substrate, the character of the substrate itself, and the time between iodine application and plant cultivation. The loss of iodine from soil via volatilization can also be a limiting factor to iodine bioavailability. Our results provide additional information on iodine mobility and behavior in soil and suggest plants’ essential role in biogeochemical cycle of iodine. We also highlighted importance of iodine source and speciation on the base level of the food chain where iodine mobility and bioavailability is limited by its chemical form, substrate characteristics, and intensity of natural biogeochemical processes related to iodine biotransformation.

Effects of Pisolithus tinctorius and Cenococcum geophilum inoculation on pine in copper-contaminated soil to enhance phytoremediation

ABSTRACTWe used Pisolithus tinctorius and Cenococcum geophilum to determine the copper (Cu) resistance of ectomycorrhizal (ECM) fungi and their potential for improving phytoremediation of Cu-contaminated soil by Chinese red pine (Pinus tabulaeformis). The results showed that nutrient accumulation in C. geophilum mycelium was significantly lower under higher Cu concentrations in the soil, which was not observed in P. tinctorius. Meanwhile, P. tinctorius exhibited greater Cu tolerance than C. geophilum. Inoculation with ECM fungi significantly improved the growth of pine shoots planted in polluted soil in pot experiments (p < 0.01). The total accumulated Cu in pine seedlings planted in Cu-contaminated soil increased by 72.8% and 113.3% when inoculated with P. tinctorius and C. geophilum, respectively, indicating that ECM fungi may help their host to phytoextract heavy metals. Furthermore, the majority of the total absorbed metals remained in the roots, confirming the ability of ECM fungi to promote heavy metal phytostabilization. There were no differences between the effects of the two fungi in helping the host stabilize and absorb Cu, even though they have different Cu tolerances. Inoculation with ECM fungi can benefit plant establishment in polluted environments and assist plants with phytoremediating heavy-metal-contaminated soils.

Immobilization of Lead by Alishewanella sp. WH16-1 in Pot Experiments of Pb-Contaminated Paddy Soil

This study investigates the effectiveness and mechanism of decreasing the bioavailability of Pb in bacterial culture and in pot experiments of Pb-contaminated paddy soil by Alishewanella sp. WH16-1. The WH16-1 strain was isolated from mine soil and exhibited high resistances to many heavy metals, especially to Pb2+ (2070 mg/L) and Cr (VI) (2340 mg/L). During cultivation of the WH16-1 strain with the addition of 100 mg/L Pb2+, Pb2+ was precipitated, and 84.13 % of Pb2+ was removed in 72 h. The precipitant was observed by transmission electron microscopy (TEM) and further confirmed to be PbS by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The WH16-1 strain was incubated in Pb2+-added paddy soil pot experiments for 60 days and compared with the uninoculated Pb2+-added paddy soil. Comparison showed that the exchangeable and carbonate-bound Pb in the paddy soil decreased by 14.04 and 10.69 % (P < 0.05), respectively. The Fe-Mn oxide-bound Pb, organic matter-bound Pb and the residual Pb increased by 4.47, 19.40, and 22.78 % (P < 0.05), respectively. Compared with the uninoculated Pb2+-added paddy soil, the dry weight of rice significantly increased by 28.59 %, and the Pb concentrations in rice, husk, leaves, and culms in Pb2+-added paddy soil pot experiment incubated with the WH16-1 strain significantly decreased by 26.18, 26.94, 26.61, and 25.56 % (P < 0.05), respectively. These results suggest that Alishewanella sp. WH16-1 can reduce the bioavailability of Pb in soil. This bacterium may be applicable for the biological stabilization of Pb in Pb-contaminated paddy soil.

Characterization of cadmium-resistant bacteria and their potential for reducing accumulation of cadmium in rice grains

Cadmium (Cd) pollution is a serious widespread environmental problem that not only destroys the microbial ecology of soil and decreases crop production, but also poses a serious risk to human health. Many methods have been used for the remediation of Cd pollution but none of these is totally satisfactory. Microbial remediation strategies have attracted increasing interest since they are environmentally friendly and cost-effective. In the present study, three Cd-resistant bacteria were isolated and evaluated for potential application in Cd bioremediation. Based on their morphological, physiological and biochemical characteristics, together with 16S rDNA gene sequence analyses, bacteria were identified as Stenotrophomonas acidaminiphila (2#), Pseudomonas aeruginosa (9#) and Delftia tsuruhatensis (12#). Pseudomonas aeruginosa showed very high tolerance to metals, especially Cd (2200mg/L), Zn (1800mg/L) and Pb (1200mg/L), and is thought to be a multi-metal-resistant bacterium. Pseudomonas aeruginosa was also sensitive to 13 different antibiotics. The effects of the bacterial strains on the growth of rice plants and their ability to reduce Cd accumulation from Cd-contaminated soils in pot experiments were also evaluated. For Oryza sativa L. A grown in contaminated soil (3mg/kg Cd), the accumulation of Cd was decreased by 31.2 and 25.5% in brown rice and polished rice, respectively, by strain 9#; Pseudomonas aeruginosa was more effective in reducing Cd accumulation in rice grains than a mixture of strains. For Oryza sativa L. B, a mixture of strains acting synergistically was more effective than a single strain in reducing Cd accumulation; treatment with mixed strains (strains+3mg/kg Cd) resulted in 41.3, 35.9, and 32.6% reductions in Cd accumulation in unhulled rice, brown rice and polished rice, respectively. Although different results were obtained for two rice varieties, it can still be concluded that Cd-resistant bacteria are suitable for reducing Cd accumulation in rice grains and show potential for bioremediation of Cd-contaminated soils.

Heavy metal accumulation and effects on growth, biomass and physiological processes in mustard

Mustard (Brassica juncea) var. Pusa Jaikisan was grown in a pot experiment in soil supplemented with different concentrations of nickel and chromium (50 and 100 mg kg−1 soil), lead (100 and 200 mg kg−1 soil), cadmium (5 and 10 mg kg−1 soil) and mercury (25 and 50 mg kg−1 soil) as a leafy vegetable. The study revealed that as the contamination level increased significant reductions were observed in biomass, photosynthetic rate and chlorophyll a and b contents as compared to control plants. However, plant’s stress tolerance mechanisms, including proline content and activity of antioxidant enzyme increased under different treatments. Mercury treatment recorded greater negative effects on the crop.

Regulatory effects of sulfur on oilseed rape (Brassica napus L.) response to selenite

ABSTRACTSelenite is a form of selenium (Se) commonly found in Se-excessive soils. To regulate the Se content in plants in high-Se areas, a potted soil experiment was performed on oilseed rape (Brassica napus L.) to evaluate the effects of varied amounts of sulfur (S) on the biomass, accumulation and distribution of Se in B. napus under the conditions of different amounts of Se in the soil. The results showed that the seedlings of B. napus were more sensitive to Se than the mature plants were. The addition of S significantly alleviated the growth inhibition in seedlings and facilitated the growth of mature plants under higher Se (15 mg kg−1) conditions. S treatment significantly decreased soil pH within the range of 0.22–0.60. An appropriate moderate amount (150 mg kg−1) of S exerted the strongest inhibition on Se concentration and accumulation in B. napus at the seedling stage, but a higher amount (300 mg kg−1) of S led to a more significant decrease in the mature plants under higher Se conditions, with the maximum reduction in various parts of B. napus reaching 51.3–60.9% and 42.5–53.4%, respectively. The application of S only affected the uptake of Se, and not the translocation of Se; the accumulation of Se in B. napus follows the sequence of pod ≈ stem > rapeseed > root, and the distribution ratio is approximately 1.00:0.97:0.69:0.49. Overall, the application of S alleviated the inhibitory effect on growth caused by excessive Se by reducing the Se concentration in B. napus and facilitating its growth, suggesting that S treatment is a suitable and highly cost-effective method to regulate the content of Se in B. napus.

Aluminium alleviates fluoride toxicity in tea (Camellia sinensis)

Tea is a strong accumulator of both aluminium (Al) and fluoride (F). We tested the hypothesis that Al helps detoxify F in tea plants by forming Al-F complexes. Tea plants were grown hydroponically with a range of Al and F concentrations and in a soil pot experiment with amendments of NaF and acids. Growth and the uptake of F and Al were determined. Chemical species of F in the nutrient solutions and the cell saps of roots and leaves were determined by 19F NMR. In hydroponic experiments, F inhibited the growth of new roots and shoot tips in the absence of Al in the nutrient solutions, whereas Al stimulated root growth and alleviated the toxicity of F. Aluminium generally increased F concentration in roots but decreased F concentration in leaves. Geochem-PC calculations and 19F NMR showed the presence of AlF2+, AlF2 + and AlF3 0 in the nutrient solutions when Al and F were present. Aluminium markedly decreased the NMR peak of free F in the cell saps from roots and leaves. An Al-F complex likely to be AlF2+ was detected in the leaf cell sap from the plants treated with both F and Al. In the soil pot experiment, F caused leaf necrosis when the leaf Al to F molar ratio was smaller than 1. Tea plants are sensitive to F toxicity in the absence of Al. Aluminium alleviates F toxicity in tea by forming Al-F complexes.

Selection of effective strains ofBradyrhizobiumfor Caatinga stylo (Stylosanthes seabrana)

Caatinga stylo ( Stylosanthes seabrana ) is recommended as a forage legume for permanent and long-term ley pastures on clay soils of southern (cv. Primar CPI92838B) and central (cv. Unica CPI110361) Queensland. The release of the 2 cultivars was contingent on the availability of an effective and persistent strain of Bradyrhizobium, because suitable effective nitrogen-fixing strains do not occur naturally in the soils of the target regions. Effective strains of Bradyrhizobium (strains CB3480 and CB3481), suitable as inocula for Caatinga stylo, were selected from nodule material collected in Bahia, Brazil. This paper documents soil-pot and field experiments that led to the selection of these persistent and effective strains of Bradyrhizobium and the eventual release of CPI92838B and CPI110361, respectively, as cvv. Primar and Unica. Keywords: Inoculation, nitrogen fixation, nodulation, soil temperature, survival. DOI: 10.17138/TGFT(4)54-70

OsWRKY74, a WRKY transcription factor, modulates tolerance to phosphate starvation in rice.

The WRKY transcription factor family has 109 members in the rice genome, and has been reported to be involved in the regulation of biotic and abiotic stress in plants. Here, we demonstrated that a rice OsWRKY74 belonging to group III of the WRKY transcription factor family was involved in tolerance to phosphate (Pi) starvation. OsWRKY74 was localized in the nucleus and mainly expressed in roots and leaves. Overexpression of OsWRKY74 significantly enhanced tolerance to Pi starvation, whereas transgenic lines with down-regulation of OsWRKY74 were sensitive to Pi starvation. Root and shoot biomass, and phosphorus (P) concentration in rice OsWRKY74-overexpressing plants were ~16% higher than those of wild-type (WT) plants in Pi-deficient hydroponic solution. In soil pot experiments, >24% increases in tiller number, grain weight and P concentration were observed in rice OsWRKY74-overexpressing plants compared to WT plants when grown in P-deficient medium. Furthermore, Pi starvation-induced changes in root system architecture were more profound in OsWRKY74-overexpressing plants than in WT plants. Expression patterns of a number of Pi-responsive genes were altered in the OsWRKY74-overexpressing and RNA interference lines. In addition, OsWRKY74 may also be involved in the response to deficiencies in iron (Fe) and nitrogen (N) as well as cold stress in rice. In Pi-deficient conditions, OsWRKY74-overexpressing plants exhibited greater accumulation of Fe and up-regulation of the cold-responsive genes than WT plants. These findings highlight the role of OsWRKY74 in modulation of Pi homeostasis and potential crosstalk between P starvation and Fe starvation, and cold stress in rice.

Phytotoxicity and detoxification mechanism differ among inorganic and methylated arsenic species in Arabidopsis thaliana

Plants are able to take up inorganic arsenic (As) and methylated As, but whether the mode of phytotoxicity and the detoxification mechanism differ between different As species remains unclear. This study aimed to investigate the differences in phytotoxicity and detoxification mechanism between arsenate [As(V)], monomethylarsonic acid [MMA(V)] and dimethylarsinic acid [DMA(V)]. Arabidopsis thaliana was grown in agar-solidified medium, hydroponic or soil pot experiments. Root and shoot growth, seed production, As accumulation and oxidative stress indicators of wild-type plants exposed to As(V), MMA(V) and DMA(V) were compared. The role of thiols in As detoxification was investigated using a specific inhibitor of glutathione (GSH) biosynthesis and the mutants defective in GSH synthesis (cad2-1), phytochelatin (PC) synthesis (cad1-3) or tonoplast transporters for As(III)-PCs (abcc1-2). Methylated As species, especially DMA(V), were more toxic than As(V) for growth and seed production in A. thaliana. Methylated As species were more efficiently translocated from roots to shoots and from shoots to seeds than As(V). DMA(V) exposure resulted in a greater oxidative stress than other As species. As(V) and MMA(V) induced the production of non-protein thiols (NPT), but DMA(V) did not. The GSH inhibitor BSO greatly enhanced the sensitivity to As(V) and MMA(V), but decreased the sensitivity to DMA(V). The mutants cad1-3, cad2-1 and abcc1-2 were similarly hypersensitive to As(V) and MMA(V), but not to DMA(V). As(V) and MMA(V) enhanced the expression of the sulphur assimilation genes encoding ATP Sulphurylase (ATPS) and adenosine-5′-phosphosulphate reductase (APR1) more than DMA(V). DMA(V) is more toxic to A. thaliana than As(V) or MMA(V). The detoxification mechanism for MMA(V) is similar to that for As(V), involving thiol production, complexation with PCs and vacuolar sequestration. This mechanism is ineffective for the detoxification of DMA(V).

Indigenous arbuscular mycorrhizal (AM) fungi contribute to wheat phosphate uptake in a semi-arid field environment, shown by tracking with radioactive phosphorus

The aim was to determine the quantitative contribution of naturally-occurring arbuscular mycorrhizal (AM) fungi to phosphorus (P) uptake by wheat in the field in a semi-arid, agricultural environment. Findings were compared with a pot experiment in the same soil in order to assess the predictive value of pot experiments. Similar compartmented systems were used in both experiments, to provide radioactive P only to the AM fungal assemblage. Delivery of P to the plants was tracked and the contributions of the AM uptake pathway quantified. AM colonisation from the soil in both experiments was low and variable. A range of colonisation morphologies indicated the presence of several different AM fungi. By 44 d (pot experiment) and 67 d (field experiment) the AM pathway delivered P to all 10 plants in pots and 115/120 plants in the field. The contributions were 3–40% of total P to whole plants in pots and 6.5–21% to shoots in the field, equivalent to means of approximately 0.48 and 0.16kgPha−1, respectively (minimum estimates, see text). There was no significant relationship between % root length colonised and amount of P delivered via the AM pathway in either experiment. Even with low AM colonisation, the natural assemblage of indigenous AM fungi made a significant contribution to P uptake by wheat, a plant that is often regarded not to benefit from AM colonisation. We conclude that it is feasible to use compartmented systems in the field to estimate the quantitative contribution of AM fungi to P uptake by plants and that it is unwise to ignore the AM contribution in research aimed to understand mechanisms potentially contributing to P uptake efficiency.

In Situ Measurement of Ammonia Concentration in Soil Headspace Using Fourier Transform Mid-Infrared Photoacoustic Spectroscopy

Ammonia (NH3) volatilization is one of the important pathways of nitrogen loss in alkaline soil, and the NH3 concentration in soil headspace is directly linked with the NH3 volatilization. Ammonia was characterized by Fourier transform mid-infrared photoacoustic spectroscopy (FTIR-PAS) and two typical absorption bands in the region of 850–1200 cm−1 were observed, which could be used for the prediction of NH3 concentration in the soil headspace. An alkaline soil from North China was involved in the soil incubation, pot and field experiments under three fertilization treatments (control without N input (CK), urea and coated urea). Ammonia concentrations in the soil headspace were determined in each experiment. In the soil incubation experiment, the NH3 emissions were initiated by the N input, reached the highest concentration on day 2, and decreased to the level as measured in CK after 8 d, with significantly higher NH3 emissions in the urea treatment compared to coated urea treatment, especially during the first 4 d. The NH3 concentration in soil headspace of the pot experiment showed the similar dynamics as that in the incubation experiment; however, the NH3 concentration in the soil headspace in the field experiment demonstrated a significantly different emission pattern with those of the incubation and pot experiments, and there was a 4-d delay for the NH3 concentration. Therefore, the NH3 concentration in the incubation and pot experiments could not be directly used to model the real NH3 emission in the field due to the differences in fertilization method and application rate as well as soil temperature and soil disturbance. It was recommended that light irrigation in the second week after fertilization and involvement of controlled release coated urea could be used to significantly decrease N loss from the perspective of NH3 volatilization.

Response of Leucaena leucocephala (Lam.) De Wit (Leucaena) Provenances to Aluminium in Potted Soil Experiment

Aims: To determine the level of acid or aluminium tolerance provenances in Leucaena (Leucaena leucocephala) a favourite agroforestry tree in Kenya. Study Design: The set up was a 2-factor (provenance-aluminium) experiment in a completely randomized design with three (3) replications and data were subjected to multivariate analysis of variance. Place and Duration of Study: Potted acid soil experiments were carried out at the Maseno ICRAF/KEFRI centre and Chepkoilel campus farm, Moi University, between June 2009 and July 2010. Methodology: Potted acid soil experiments were carried out at the Maseno ICRAF/KEFRI centre (pH 4.8) and Chepkoilel campus farm, Moi University (pH 5.0) to assess the effect of varying Original Research Article Kodiago et al.; IJPSS, 7(2): 91-101, 2015; Article no.IJPSS.2015.134 92 aluminium concentrations on growth of three local leucaena provenances: K156 (Gede), K136 (Kibwezi) and KIT2724 (Kitale). Aluminium was applied at 0, 100, 200 and 300 M. The number of leaves per seedling, seedling height, root length, root collar diameter and dry weight were recorded at 60 and 120 days after planting. Results: Generally Aluminium at 100 M significantly (p0.05) enhanced growth of the seedlings at both sites. However, aluminium at  200 M reduced seedling growth. Conclusion: The Leucaena provenance K156 could be used in acid soils because it is tolerant. However, more local provenances should be screened for acid tolerance.

Population dynamics of Meloidogyne javanica and its relationship with the leaf chlorophyll content in zucchini

The relationship between the initial (Pi) and final (Pf) population densities of Meloidogyne javanica in response to increasing initial inoculum levels and the effect on yield in zucchini cv. Amalthee (Cucurbita pepo L.) was determined using a geometric series of 12 Pi from 0 to 51,200 eggs/100 cm3 of soil in pot experiments in a greenhouse. The maximum multiplication rate was 425, and the equilibrium density was 701,951 eggs/100 cm3 soil. The relative yield, represented as dry top weight, fit the Seinhorst damage function model and the minimum relative yield (m) was 0.82 and the tolerance limit (T) was 402 J2/100 cm3 soil. Regression analyses indicated a negative relationship between the Pi and the leaf chlorophyll content (LCC) 40, 50, 60, and 70 days post-inoculation. The Pi and LCC fit the Seinhorst damage-function model. Zucchini cv. Dyamant was planted in a plastic greenhouse with a range of M. javanica Pi from 0 to 861 J2/100 cm3 soil. The maximum multiplication rate of M. javanica under field conditions was 3093, and the equilibrium density was 1485 J2/100 cm3 soil. The relationship between Pi and relative yield, represented as fruit weight, fit the Seinhorst damage function model (P < 0.0001, R2 = 0.78); m was 0.48, and T was 0.02 J2/100 cm3 soil.

Preparation of an Environmental Friendly Slow Release Nitrogen Fertilizer

An environmental friendly slow-release urea fertilizer with double films (SUFDF) was prepared by using dialdehyde starch urea resin (DASU) as inner coating and polylactic acid (PLA) as outer materials. The structural, chemical characteristics and morphology of the SUFDF were characterized by FTIR, element analysis and SEM. Its efficiency in slowing the nitrogen release was examined via soil leaching and pot experiments. The experimental results indicated that the introduction of hydrophobic PLA and DASU reduced the swell ability of the fertilizer, which made it can provide nitrogen persistently at the early farming. After the urea dissolved, the DASU in the fertilizer would continue to release nitrogen due to its good slow-release property. So this fertilizer would have potential applications in modern agriculture and horticulture.

Analysis of Material Properties with Biochar Improve Indian Mustard (&lt;i&gt;Brassica juncea&lt;/i&gt;) Growth in Acidic Soil in Northern China

Two biochars were prepared at 400 °C from peanut shell and Chinese medicine material residue, and their surface properties were measured by scanning electron microscopy (SEM) and electron dispersive X-ray analysis (EDX). The two biochars were mixed at a ratio of 1:1, and then was applied to an acidic soil collected from a cropland in Huangdao district of Qingdao, Shandong province, China. The results of soil incubation and pot experiments showed that biochar applications to the acidic soil (1% and 5%) increased pH value from 5.8 to 6.1 and 6.7, improved Indian mustard (Brassica juncea) seed germination rate by 10% and 15%, respectively, and the shoot and root dry weight were significantly increased by 8.3%/28.5% and 11.5%/26.9%.

Effects of elevated copper levels on biological nitrogen fixation and occurrence of rhizobia in a Tanzanian coffee-cropped soil

A study was conducted to investigate the effects of increasing copper concentration in soil on rhizobial occurrence and the process of biological nitrogen fixation. Two slow-growing bradyrhizobial strains CP1 and GM8 and two fast-growing rhizobial strains PV1 and PV2 were studied by comparing their performance under increasing copper concentrations in greenhouse-based assays involving modified Leonard jar assemblies and potted-soil experiments. Additionally, field samples from soils grown to coffee and subjected to long-term use of copper-based fungicides were analyzed for their total indigenous rhizobial populations using the most probable number-plant infection technique. Results indicated that elevated copper levels in the growth medium had inhibitory effects on nodulation, biological N2 fixation and overall rhizobial numbers in soil. Significant (p= 0.05%) reductions in fresh nodule mass, fresh nodule volume and total shoot nitrogen were recorded when copper concentration was increased from 0 to 100 ppm in both modified Leonard jar assemblies and potted-soil trials. Effective decrements in all the three parameters of fresh nodule mass, fresh nodule volume and total shoot nitrogen were more pronounced with the slow-growing bradyrhizobial strains of CP1 and GM8 than with the fast-growing PV1 and PV2. The MPN-plant infection technique results showed a non-significant (p=0.05) but substantial decrement in rhizobial and bradyrhizobial numbers when the copper-contaminated field soil (82.5 mgCu/g soil) was compared to a control soil (1.8 mgCu/g soil). The study concludes, therefore, that elevated levels of copper in soil could be harmful to free-living rhizobia and their abilities to fix N2 in respective symbiotic associations with legume species. Such negative effects were more pronounced in the slow-growing bradyrhizobial than rhizobial species used.

A comparative study on plant morphology, gas exchange parameters, and antioxidant response of Ocimum basilicum L. and Origanum vulgare L. grown on industrially polluted soil

The effects of Cd, Pb, and Zn uptake on plant morphology, photosynthetic parameters, antioxidant potential, and essential oil yield and quality in Ocimum basilicum L. and Origanum vulgare L. plants were evaluated. The plants were grown as a pot experiment in soil heavily polluted with Cd and Pb and on unpolluted soil. Both plants accumulated Cd, mainly in the roots, while Pb occurred in the oregano shoots only. The leaf blade thickness of both plants increased when grown in polluted soil. Basil plants responded to the action of heavy metals with increases in gas exchange, stomatal conductivity, and transpiration, but water-use efficiency declined. Gas exchange and transpiration were reduced in treated oregano plants, but stomatal conductivity and water-use efficiency increased significantly. In basil, the increased levels of low molecular weight antioxidants such as phenols and flavonoids were observed, while in oregano, ascorbate, glutathione, and phenols were enhanced. Enzymatic antioxidant defense was observed in both plants when grown in contaminated soil, mainly with glutathione peroxidase, quaiacol peroxidase, glutathione S-transferase, and glutathione reductase. Accumulated levels of Cd, Pb, and Zn in plant organs resulted in a reduction in essential oil yield in basil only.

Effects of Phosphorus Availability on Plant Growth and Soil Nutrient Status in the Rice/Soybean Rotation System on Newly Cultivated Acidic Soils

Acid soils are worldwide spread, where low phosphorus (P) availability is considered as the major limiting constraint for crop growth, particularly on the newly cultivated acidic soils. Traditionally, the rotation system of rice with leguminous crops has been often used on acid soils. However, little is known about how P availability affects this traditional rotation system on acid soils. In the present study, two years of soil pot experiments had been done using rice (Oryza sativa L.) as the first crop and soybean (Glycine Max L.) as the second crop. The results showed that rice growth were significantly affected by P fertilization on acid soils. Sufficient P application increased plant height, shoot biomass, tiller number, and panicle dry weight compared to that of no P fertilization in both two years’ studies. The growth of following crop soybean was also influenced by P supply, and the P efficient genotype HX1 exhibited more adaptive to low P than the P inefficiency genotype BD2, as reflected by better growth of HX1 than BD2. Rhizosphere pH and soil nutrient status was significantly influenced by the rotation system. An increased tendency of rhizosphere pH was observed after the growth of rice and soybean. Soil N concentration was significantly increased after planting HX1 but not BD2. Furthermore, rice rotated with HX1 resulted in higher P fertilizer use efficiency (PFUE). Taken together, we conclude that the rice-soybean rotation with optimal P supply is a suitable agricultural mode on acid soils, and rotating with the P efficient soybean genotype could benefit more in soil nutrient status, which might increase the agriculture sustainability on acid soils.