Morphological and physiological responses of Dalbergia odorifera T. Chen seedlings to different culture substances.
Yue Xiao-Hui,Miao Ling-Feng,Yang Fan,Nawaz Mohsin
Dalbergia odorifera T. Chen seedlings do not grow well in the typical red soils of tropical regions. Eighteen culture substances filled with different substrate combinations and proportions of red soil, coconut coir powder, deciduous leaf powder, and sand were used as to determine their effects on the growth, root system development, dry matter accumulation and allocation, leaf relative electrolyte leakage, chlorophyll content, root superoxide dismutase activity, root malondialdehyde content, and total soluble sugar content of D. odorifera. Results demonstrated that different substrate combinations and proportions had different effects on the performance of D. odorifera. All mixed substrates were better than any single substrate. The suitable substrate combinations and proportions of sand, coconut coir powder, and deciduous leaf powder mixed with red soil improved the growth, root architecture, and physiological characteristics of D. odorifera seedling. For example, groups C1-2 (coconut coir/red soil = 2/2, v/v, the same below) and C3-2 (red soil/sand = 2/2) exerted the best effects on plant growth and biomass accumulation. Groups C1-2, C2-2 (deciduous leaf powder/red soil = 2/2), and C3-2 remarkably enhanced root system development. Group C6 (coconut coir/red soil/sand = 1/1/1) substantially promoted root nodule development. Group C3-1 (red soil/sand = 3/1) exhibited the best effects on physiological characteristics. On the basis of the comprehensive evaluation of Euclid's multidimensional space mathematical model, we found that the suitable substrate combinations followed the order of C1-2 > C3-1 > C2-2. This research provides scientific guidance for the proper seedling culture of D. odorifera and the rational utilization of solid wastes such as coconut coir and deciduous leaves of Ficus elastica.
Responses of the rhizosphere bacterial community in acidic crop soil to pH: Changes in diversity, composition, interaction, and function.
Wan Wenjie,Tan Jiadan,Wang Yi,Qin Yin,He Huangmei,Wu Huiqin,Zuo Wenlong,He Donglan
The Science of the total environment
Soil pH is an important predictor of bacterial community composition and diversity. Examining the effects of pH on diversity, structure, interaction, and function of rhizosphere bacterial communities in acidic crop soils provide valuable information for knowing potential role of rhizosphere bacteria in crop yield. Here, we collected soils from artificial greenhouses and applied Illumina Miseq sequencing, quantitative PCR techniques, multiple ecological analysis methods, including topological analysis and functional profiling to analyze our data and validate our hypotheses. We found that the soil physicochemical properties, species diversity, and rhizosphere bacterial community composition were significantly affected by the degree of soil acidification (pH < 5.5 and pH > 5.5) but not vegetation type. Additionally, bacterial absolute abundance increased with higher pH. The 18 soil samples were clustered into two distinct groups of pH < 5.5 and pH > 5.5 at the OTU level, and soil pH had more of an effect on bacterial community composition compared to the other physicochemical variables. In addition, rhizosphere bacteria might presented relatively less competition for survival in pH < 5.5 soils, and bacterial community functions, including nutrient (i.e., carbon, nitrogen, phosphorus, and sulphur) cycling-related enzymes and proteins, were downregulated in more acidic soils (pH < 5.5) based on sequence analysis. To our knowledge, this report is the first to show that pH is a key factor affecting the diversity, structure, interaction, and function of rhizosphere bacterial communities in acidic crop soil in artificial greenhouses. Our findings emphasize that community function and structure of rhizosphere bacteria are closely correlated in more acidic soils, and the decreased crop yield may be correlated with attenuation of the function of the rhizosphere bacterial community.
Acquisition of rock phosphate by combined application of ammonium fertilizers and Bacillus amyloliquefaciens FZB42 in maize as affected by soil pH.
Mpanga I K,Ludewig U,Dapaah H K,Neumann G
Journal of applied microbiology
AIMS:The use of plant growth-promoting micro-organisms (PGPMs) to improve plant-nutrient acquisition has a long history but reproducibility remains a challenge. Recent findings suggest an important role of suitable inoculant-fertilizer combinations for the expression of PGPM-effects, particularly with respect to nitrogen (N) supply. In face of the well-documented N form effects on rhizosphere pH, this study addressed the impact of ammonium-assisted PGPM-interactions on the acquisition of sparingly soluble calcium-phosphates as affected by soil pH. METHODS AND RESULTS:The effects of stabilized ammonium fertilization combined with the PGPM inoculant Bacillus amyloliquefaciens FZB42 on the acquisition of rock phosphate in maize were examined on two soils (moderately acidic-pH 5·6 and alkaline-pH 7·8). On the two contrasting soils, FZB42 improved the P status and promoted plant growth by different mechanisms. On the acidic soil, a combination of ammonium-fertilization with FZB42 increased P-acquisition by Rock P solubilization via rhizosphere acidification but P-supply in the noninoculated control was already sufficient to meet the plant demands. By contrast, on the alkaline soil, plant growth-promotion was associated with FZB42-induced root growth stimulation. CONCLUSION:The results suggest a significant impact of soil pH on performance and the mode of action of PGPM inoculants, to be considered for practical applications. SIGNIFICANCE AND IMPACT OF THE STUDY:The study advanced existing knowledge on PGPM-assisted P solubilization as affected by different soil properties. The results suggest perspectives for management options to be considered for efficient use of PGPMs in terms of selecting application strategies with compatible PGPM-fertilizer combinations, depending on soil pH conditions.
Impact of plant growth promoting rhizobacteria on different forms of soil potassium under wheat cultivation.
Ghadam Khani A,Enayatizamir N,Norouzi Masir M
Letters in applied microbiology
This study aimed to investigate the effect of some plant growth promoting rhizobacteria with potassium dissolution ability on different forms of potassium in soil under the cultivation of wheat. The factorial experiment was conducted as a randomized complete design with three replications in greenhouse conditions. The treatments consisted of bacterium inoculation (without inoculation, Enterobacter cloacae Rhizo_33, Pseudomonas sp. Rhizo_9, consortium of Enterobacter cloacae Rhizo_33 and Pseudomonas sp. Rhizo_9), potassium application (2·87 mg K kg of soil and without potassium application).The results indicated that soils treated with Enterobacter cloacae Rhizo_33, either receiving potassium or not, maintain a higher amount of exchangeable K (337 mg kg ) and water-soluble K (1·25 and 1·31 meq L with and without K application respectively). The nonexchangeable K and nitric acid-extractable K values were decreased by inoculating bacterial strains. The grain yield was significantly enhanced by the inoculation of bacterial strains irrespective of rates of potassium application. About 19·16% increase of grain yield was recorded by inoculation of Enterobacter cloacae Rhizo_33 and without potassium application. A significantly greater amount of K uptake in grain was obtained in soils treated with Enterobacter cloacae Rhizo_33, with and without the application of potassium (28·7 and 30·7 mg per pot respectively). There was a significant (P < 0·01) and positive correlation between grain yield and grain, shoot and root K uptake. Potassium uptake had a positive significant correlation with water-soluble K and exchangeable K; it was negatively correlated with K (HNO ). The data suggested that inoculation of soil with mentioned bacteria can improve plant growth and potassium uptake. SIGNIFICANCE AND IMPACT OF THE STUDY: As one of the macronutrients, Potassium is the most abundant absorbed cation in most plants and exists in soil in different forms. Soluble and exchangeable forms of potassium (K) are important with regard to plant uptake. K-solubilizing bacteria can convert insoluble potassium to soluble forms; therefore using K-solubilizing bacteria as biofertilizers is a sustainable solution for the improvement of plant growth, nutrition, root growth, plant competitiveness and reducing the use of potassium chemical fertilizer.
Effect of foliar and soil application of plant growth promoting bacteria on growth, physiology, yield and seed quality of maize under Mediterranean conditions.
Efthimiadou Aspasia,Katsenios Nikolaos,Chanioti Sofia,Giannoglou Marianna,Djordjevic Nikola,Katsaros George
The use of plant growth promoting bacteria (PGPB) as biostimulants favors the increase of crop productivity and the improvement of yield quality. The main objective of the present study was to investigate the effect of the PGPB biostimulants (Azotobacter chroococcum, Bacillus subtilis, Bacillus megatherium and their mixes) and the application method (foliar and soil) on the growth, the physiology, the yield and the quality of maize. The obtained results showed that A. chroococcum treatment increased the chlorophyll content up to 6.1%, the photosynthetic rate up to 18.4% and the transpiration rate up to 34.3%. The highest maize yields were performed by the treatments B. megatherium (244.67 g) and the mix of A. chroococcum and B. subtilis (1:1) (243.67 g) when applied on the soil. The Soil application of the PGPB resulted in increased yield of maize from 5.5 to 13.4% compared to control treatment. Concerning quality characteristics, B. subtilis treatment increased total solids content in harvested maize seeds by 92%, as well as crude fiber content by 46% compared to control. The results confirmed that the use of PGPB could contribute as a new cultivation practice for sustainable growth, productivity and quality of grain crops.
Biochar with near-neutral pH reduces ammonia volatilization and improves plant growth in a soil-plant system: A closed chamber experiment.
Mandal Sanchita,Donner Erica,Smith Euan,Sarkar Binoy,Lombi Enzo
The Science of the total environment
Ammonia (NH) volatilization is considered as one of the major mechanisms responsible for the loss of nitrogen (N) from soil-plant systems worldwide. This study investigated the effect of biochar amendment to a calcareous soil (pH 7.8) on NH volatilization and plant N uptake. In particular, the effect of biochar's feedstock and application rate on both NH volatilization and plant growth were quantified using a specially designed closed chamber system. Two well-characterized biochars prepared from poultry manure (PM-BC) and green waste compost (GW-BC) were applied to the soil (0, 0.5, 1, 1.5 and 2% w/w equivalent to 0, 7.5, 15, 22 and 30 t ha) and wheat (Triticum aestivum, variety: Calingiri) was grown for 30 days. Both PM-BC and GW-BC decreased NH volatilization to a similar degree (by 47 and 38%, respectively), in the soil-plant system compared to the unamended control. Higher plant biomass production of up to 70% was obtained in the closed chamber systems with the addition of biochar. The increase in plant biomass was due to the reduction in N loss as NH gas, thereby increasing the N supply to the plants. Plant N uptake was improved by as much as 58% with biochar addition when additional NPK nutrients were supplied to the soil. This study demonstrates that the application of biochars can mitigate NH emission from calcareous agricultural cropping soil and that the retained N is plant-available and can improve wheat biomass yield.
Effect of photosynthetically elevated pH on performance of surface flow-constructed wetland planted with Phragmites australis.
Yin Xiaole,Zhang Jian,Hu Zhen,Xie Huijun,Guo Wenshan,Wang Qingsong,Ngo Huu Hao,Liang Shuang,Lu Shaoyong,Wu Weizhong
Environmental science and pollution research international
Combination of emergent and submerged plants has been proved to be able to enhance pollutant removal efficiency of surface flow-constructed wetland (SFCW) during winter. However, intensive photosynthesis of submerged plants during summer would cause pH increase, which may have adverse effects on emergent plants. In this study, nitrogen transformation of lab-scale SFCW under pH gradient of 7.5, 8.5, 9.5 and 10.5 was systematically investigated. The results showed that total nitrogen (TN) removal efficiency decreased from 76.3 ± 0.04 to 51.8 ± 0.04 % when pH increased from 7.5 to 10.5, which was mainly attributed to plant assimilation decay and inhibition of microbe activities (i.e., nitrite-oxidizing bacteria and denitrifiers). Besides, the highest sediment adsorption in SFCW was observed at pH of 8.5. In general, the combination of submerged and emergent plants is feasible for most of the year, but precaution should be taken to mitigate the negative effect of high alkaline conditions when pH rises to above 8.5 in midsummer.
Effect of Soil pH on the Growth, Reproductive Investment and Pollen Allergenicity of L.
Gentili Rodolfo,Ambrosini Roberto,Montagnani Chiara,Caronni Sarah,Citterio Sandra
Frontiers in plant science
Despite the importance of soil reaction for alien plant establishment, few and incomplete studies have included this key factor so far. In this study, we investigated the effects of soil pH on the germination, growth (plant height, width, dry weight, etc.) and reproductive investment (inflorescence size and n° of flowers) of (common ragweed), an allergenic species that is highly invasive and alien in Europe, through a replicated experiment in controlled conditions. In addition, we determined if soil pH has an effect on the total pollen allergenicity of the species. After preliminary germination tests on agar at different pH (from pH4 to pH8), plants were grown in natural soils with pH values of 5 (acid), 6 (sub-acid) and 7 (neutral) obtained by modifying a natural soil by liming methods (calcium hydroxide solution). Results showed that plants grown at pH7 were shorter and developed leaves at a slower rate than those grown at pH5 and pH6; plants grown at pH7 did not produce flowers and pollen. We also observed that, at pH5 and pH6, larger plants (as assessed by the dry weight of the aerial biomass) had both larger and more numerous inflorescences and emitted pollen earlier. Finally, the IgE-binding signal was higher in pollen samples collected from plants grown at pH5 (Integrated Optical Density, IOD, range: 1.12-1.25) than in those grown at pH6 (IOD range: 0.86 -1.03). Although we acknowledge the limitations of only testing the effects of pH in controlled conditions, this study suggests that soil pH greatly affects the growth and development of and indicates that it may have a role in limiting the distribution and hazardousness of this plant. Future field tests should therefore assess the effectiveness of liming in the management and control of ragweed and other alien species.
Effect of pH and citric acid on the growth, arsenic accumulation, and phytochelatin synthesis in Eupatorium cannabinum L., a promising plant for phytostabilization.
González Héctor,Fernández-Fuego Daniel,Bertrand Ana,González Aída
Environmental science and pollution research international
Heavy-metal contamination of soils has increased in the last decades due to anthropogenic and industrial activities. Arsenic is one of the pollutants that is commonly found in industrial soils and is toxic for both plants and humans. The pH of the soil or the culture medium is one of the most important factors that interferes with the bioavailability of this metalloid to the plant. The addition of chelating agents, such as citric acid (CA), can increase the absorption of As by plants. Therefore, the objective of this work is to study the effect of the pH and the exogenous addition of citric acid on the growth, As accumulation, and thiol compounds in Eupatorium cannabinum; this plant grows naturally in contaminated soils in Asturias, Spain, and has a potential use in phytoremediation. The results showed that E. cannabinum was able to tolerate As stress even at extreme pH values and accumulated a high amounts of As in its roots, which makes it a promising species for the phytostabilization of soils polluted with this metalloid. An addition of 20 mg CA L led to increased biomass and As accumulation at acidic pH. In order to determine if thiolic compounds, such as phytochelatins, are involved in As accumulation and detoxification in E. cannabinum, we analyzed the synthesis of these compounds in the presence and absence of As and/or citric acid. Our results suggest that these thiolic compounds play a major role in As detoxification, since the presence of CA as a chelating agent reduced the amount of thiols necessary to cope with the toxicity caused by As.
Effect of Iron Source and Medium pH on Growth and Development of In Vitro.
Xiao Jie,Park Yoo Gyeong,Guo Ge,Jeong Byoung Ryong
International journal of molecular sciences
is a valuable hardwood plant with a high economical value for its medicinal and ornamental qualities. The aim of this work was to investigate the effects of the iron (Fe) source and medium pH on the growth and development of in vitro. The Fe sources used, including non-chelated iron sulfate (FeSO), iron ethylenediaminetetraacetic acid (Fe-EDTA), and iron diethylenetriaminepentaacetic acid (Fe-DTPA), were supplemented to the Multipurpose medium with a final Fe concentration of 2.78 mg·L. The medium without any supplementary Fe was used as the control. The pH of the agar-solidified medium was adjusted to either 4.70, 5.70, or 6.70. The experiment was conducted in a culture room for six weeks with 25 °C day and night temperatures, and a 16-h photoperiod with a light intensity of 50 mmol·m·s photosynthetic photon flux density (PPFD). Both the Fe source and pH affected the growth and development of the micropropagated plants in vitro. The leaves were greener in the pH 4.70 and 5.70 treatments. The tissue Fe content decreased with the increase of the medium pH. The leaf chlorophyll content was similar between plants treated with FeSO and those with Fe-EDTA. The numbers of the shoots and roots of plantlets treated with FeSO were 2.5 and 2 times greater than those of the control, respectively. The fresh and dry weights of the shoot and the root were the greatest for plants treated with Fe-EDTA combined with pH 5.70. The calcium, magnesium, and manganese contents in the plantlets increased in the pH 5.70 treatments regardless of the Fe source. Supplementary Fe decreased the activity of ferric chelate reductase. Overall, although the plantlets absorbed more Fe at pH 4.70, Fe-EDTA combined with pH 5.70 was found to be the best for the growth and development of in vitro.
Comparative effect of elicitors on the physiology and secondary metabolites in broccoli plants.
Hassini Ismahen,Rios Juan J,Garcia-Ibañez Paula,Baenas Nieves,Carvajal Micaela,Moreno Diego A
Journal of plant physiology
Elicitation is an economic and sustainable technique for increasing the content of secondary metabolites, mainly bioactive compounds, in plants grown for better human nutrition. The aim of this study was to compare the physiological responses (water relations and mineral nutrition) and the enrichment in glucosinolates (GLSs) and phenolic compounds of broccoli plants (Brassica oleracea L. var. italica) receiving different elicitation treatments. The treatments involved the priming of seeds with KCl and the exposure of plants to elicitors, including KSO and NaCl solutions and foliar sprays of methyl jasmonate (MeJA), salicylic acid (SA), and methionine (Met). The physiological response of the plants in terms of root hydraulic conductance was improved by priming with KCl and elicitation with MeJA or Met. Foliar application of Met significantly increased the plant biomass and enhanced mineral nutrition. In general, all treatments increased the accumulation of indole GLSs, but KSO and MeJA gave the best response and MeJA also favored the formation of a newly described compound, cinnamic-GLS, in the plants. Also, the use of Met and SA as elicitors and the supply of KSO increased the abundance of phenolic compounds; KSO also enhanced growth but did not alter the water relations or the accumulation of mineral nutrients. Therefore, although the response to elicitation was positive, with an increased content of bioactive compounds, regulation of the water relations and of the mineral status of the broccoli plants was critical to maintain the yield.
Alkaline soil pH affects bulk soil, rhizosphere and root endosphere microbiomes of plants growing in a Sandhills ecosystem.
Lopes Lucas Dantas,Hao Jingjie,Schachtman Daniel P
FEMS microbiology ecology
Soil pH is a major factor shaping bulk soil microbial communities. However, it is unclear whether the belowground microbial habitats shaped by plants (e.g. rhizosphere and root endosphere) are also affected by soil pH. We investigated this question by comparing the microbial communities associated with plants growing in neutral and strongly alkaline soils in the Sandhills, which is the largest sand dune complex in the northern hemisphere. Bulk soil, rhizosphere and root endosphere DNA were extracted from multiple plant species and analyzed using 16S rRNA amplicon sequencing. Results showed that rhizosphere, root endosphere and bulk soil microbiomes were different in the contrasting soil pH ranges. The strongest impact of plant species on the belowground microbiomes was in alkaline soils, suggesting a greater selective effect under alkali stress. Evaluation of soil chemical components showed that in addition to soil pH, cation exchange capacity also had a strong impact on shaping bulk soil microbial communities. This study extends our knowledge regarding the importance of pH to microbial ecology showing that root endosphere and rhizosphere microbial communities were also influenced by this soil component, and highlights the important role that plants play particularly in shaping the belowground microbiomes in alkaline soils.
Differences in pH influence the fate of CO in plants.
Law Simon R
Soils represent the largest and most stable carbon pools on Earth, exceeding even the carbon aggregate found in the atmosphere and global phytomass. However, our understanding of how CO travels from the soil to the atmosphere, and the role of plants in this journey, is not fully understood. An article in this issue of Physiologia Plantarum (Shimono et al. 2019) sheds light on this process and unearths the dramatic effect pH can have on the fate of CO in plants.
The effect of lead pollution on nutrient solution pH and concomitant changes in plant physiology of two contrasting Solanum melongena L. cultivars.
Javed Muhammad Tariq,Habib Noman,Akram Muhammad Sohail,Ali Qasim,Haider Muhammad Zulqurnain,Tanwir Kashif,Shauket Asia,Chaudhary Hassan Javed
Environmental science and pollution research international
Lead (Pb) is highly toxic to plants because it severely affects physiological processes by altering nutrient solution pH. The current study elucidated Pb-induced changes in nutrient solution pH and its effect on physiology of two Solanum melongena L. cultivars (cv. Chuttu and cv. VRIB-13). Plants were grown in black plastic containers having 0, 15, 20, and 25 mg L PbCl in nutrient solutions with starting pH of 6.0. pH changes by roots of S. melongena were continuously monitored for 8 days, and harvested plants were analyzed for physiological and biochemical attributes. Time scale studies revealed that cv. Chuttu and cv. VRIB-13 responded to Pb stress by causing acidification and alkalinization of growth medium during the first 48 h, respectively. Both cultivars increased nutrient solution pH, and maximum pH rise of 1.21 units was culminated by cv. VRIB-13 at 15 mg L Pb and 0.8 units by cv. Chuttu at 25 mg L Pb treatment during the 8-day period. Plant biomass, photosynthetic pigments, ascorbic acid, total amino acid, and total protein contents were significantly reduced by Pb stress predominantly in cv. Chuttu than cv. VRIB-13. Interestingly, chlorophyll contents of cv. VRIB-13 increased with increasing Pb levels. Pb contents of roots and shoots of both cultivars increased with applied Pb levels while nutrient (Ca, Mg, K, and Fe) contents decreased predominately in cv. Chuttu. Negative correlations were identified among Pb contents of eggplant roots and shoots and plant biomasses, leaf area, and free anthocyanin. Taken together, growth medium alkalinization, lower root to shoot Pb translocation, and optimum balance of nutrients (Mg and Fe) conferred growth enhancement, ultimately making cv. VRIB-13 auspicious for tolerating Pb toxicity as compared with cv. Chuttu. The research outcomes are important for devising metallicolous plant-associated strategies based on plant pH modulation response and associated metal uptake to remediate Pb-polluted soil.
The role of rhizosphere pH in regulating the rhizosphere priming effect and implications for the availability of soil-derived nitrogen to plants.
Wang Xiaojuan,Tang Caixian
Annals of botany
Background and Aims:A comprehensive understanding of the rhizosphere priming effect (RPE) on the decomposition of soil organic carbon (SOC) requires an integration of many factors. It is unclear how N form-induced change in soil pH affects the RPE and SOC sequestration. Methods:This study compared the change in the RPE under supply of NO3-N and NH4-N. The effect of the RPE on the mineralization of soil N and hence its availability to plant and microbes was also examined using a 15N-labelled N source. Key Results:The supply of NH4-N decreased rhizosphere pH by 0.16-0.38 units, and resulted in a decreased or negative RPE. In contrast, NO3-N nutrition increased rhizosphere pH by 0.19-0.78 units, and led to a persistently positive RPE. The amounts of rhizosphere-primed C were positively correlated with rhizosphere pH. Rhizosphere pH affected the RPE mainly through influencing microbial biomass, activity and utilization of root exudates, and the availability of SOC to microbes. Furthermore, the amount of rhizosphere primed C correlated negatively with microbial biomass atom% 15N (R2 0.77-0.98, n = 12), suggesting that microbes in the rhizosphere acted as the immediate sink for N released from enhanced SOC decomposition via the RPE. Conclusion:N form was an important factor affecting the magnitude and direction of the RPE via its effect on rhizosphere pH. Rhizosphere pH needs to be considered in SOC and RPE modelling.
The physiological and metabolic changes in sugar beet seedlings under different levels of salt stress.
Wang Yuguang,Stevanato Piergiorgio,Yu Lihua,Zhao Huijie,Sun Xuewei,Sun Fei,Li Jing,Geng Gui
Journal of plant research
Salinity stress is a major limitation to global crop production. Sugar beet, one of the world's leading sugar crops, has stronger salt tolerant characteristics than other crops. To investigate the response to different levels of salt stress, sugar beet was grown hydroponically under 3 (control), 70, 140, 210 and 280 mM NaCl conditions. We found no differences in dry weight of the aerial part and leaf area between 70 mM NaCl and control conditions, although dry weight of the root and whole plant treated with 70 mM NaCl was lower than control seedlings. As salt concentrations increased, degree of growth arrest became obvious In addition, under salt stress, the highest concentrations of Na and Cl were detected in the tissue of petioles and old leaves. N and K contents in the tissue of leave, petiole and root decreased rapidly with the increase of NaCl concentrations. P content showed an increasing pattern in these tissues. The activities of antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidase and glutathione peroxidase showed increasing patterns with increase in salt concentrations. Moreover, osmoprotectants such as free amino acids and betaine increased in concentration as the external salinity increased. Two organic acids (malate and citrate) involved in tricarboxylic acid (TCA)-cycle exhibited increasing contents under salt stress. Lastly, we found that Rubisco activity was inhibited under salt stress. The activity of NADP-malic enzyme, NADP-malate dehydrogenase and phosphoenolpyruvate carboxylase showed a trend that first increased and then decreased. Their activities were highest with salinity at 140 mM NaCl. Our study has contributed to the understanding of the sugar beet physiological and metabolic response mechanisms under different degrees of salt stress.
Environmental controls on soil pH in planted forest and its response to nitrogen deposition.
Hong Songbai,Gan Pei,Chen Anping
BACKGROUND:Soil pH is important for controlling many soil properties. The variation in soil pH can be associated with changes in climate, soil buffering system, nitrogen deposition, and plants. However, there still lacks a comprehensive study exploring the effects of all these factors on soil pH simultaneously. Here we aimed to investigate the environmental controls on the spatial variation of soil pH in planted forests across Northern China and reveal its response to different-forms of nitrogen deposition for different species of tree plantations. METHODS:We sampled 1980 soil profiles from 660 planted forest plots (3 profiles in each plot) in Northern China. We used correlation analyses and structure equation models (SEM) to explore the impacts of multiple environmental factors on soil pH. RESULTS:Climate (water balance, temperature) and soil inorganic carbon accounted for most variations of soil pH. Specifically, the concentration of hydrogen ions ([H]) varied almost isometrically with soil inorganic carbon, which was also the major buffering system in this region. Nitrogen deposition affected both soil pH values and soil buffering system. Results from structure equation model indicated that nitrate nitrogen directly decreased soil pH, while ammonium nitrogen mostly affected soil pH indirectly through its impacts on soil inorganic carbon. The responses of soil pH to nitrogen deposition were species-specific, and conifer stands tended to have higher soil acidification rate than stands of other tree species. CONCLUSIONS:Our study provides important information for understanding mechanisms controlling the spatial pattern of soil pH in planted forests and highlights the need to develop informed policies for soil resource management under increasing threats from anthropogenic nitrogen deposition.
Effects of different soil pH and nitrogen fertilizers on Bidens pilosa L. Cd accumulation.
Dai Huiping,Wei Shuhe,Skuza Lidia
Environmental science and pollution research international
Bidens pilosa L. was a Cd hyperaccumulator. This experiment determined the effects of different soil pH (adjusted by weak acid and alkali at 4.83, 6.81, and 7.84, respectively) and nitrogen ((NH)SO, Ca(NO)) on B. pilosa phytoextracting Cd in soil collected from a smelter (Cd concentration was 19.63 mg kg). The results showed that the Cd concentrations in B. pilosa were significantly higher (p < 0.05) with soil pH 4.83 treatments than those of pH 6.81 and 7.84 ones. The Cd concentration of B. pilosa grown in pH 7.84 soil was significantly lower (p < 0.05) than that in pH 6.81 soil. The extractable Cd concentration in soil was decreased (p < 0.05) with the increase of pH. Under three different pH conditions, the rhizosphere pH of B. pilosa was basically 0.2 lower than that of pH in bulk soil respectively, indicating that the hyperaccumulator had a certain acidification effect on soil. Two kinds of nitrogen fertilizers (NH)SO and Ca(NO) had no significant difference (p < 0.05) on Cd concentrations of B. pilosa, which was probably caused by the acidification effect of its rhizosphere. The biomasses of B. pilosa were not affected (p < 0.05) by different pH of soil. The photosynthetic production, antioxidative enzymes, and lipid peroxidation change trends of B. pilosa were basically consistent with its biomasses. Generally speaking, B. pilosa showed high Cd accumulation potential and strong adaptability for different soil situations.