Nutrient Solution Culture Research Articles

Nitrogen Nutrition-Induced Changes in Macronutrient Content and Their Indirect Effect on N-Metabolism Via an Impact on Key N-Assimilating Enzymes in Bread Wheat (Triticum aestivum L.)

Judicious application of nitrogen (N) fertilizers in crop production is critical for reducing the nitrate pollution of groundwater and greenhouse gas emissions. It is, thus, important to improve the nitrogen use efficiency under the reduced application of nitrogen. A genotypic variation in N-uptake and N-use efficiency particularly under low N-input conditions exists across crops that can be deciphered and exploited for environmentally sustainable farming without any significant penalty of yield and quality. The present research conducted under the nutrient solution culture aimed to explore the inherent variability in the growth response of ten genetically diverse wheat varieties to low fertilizer N-application (N-, 10 μM N) in comparison to N sufficient control (N+, 8.5 mM N) viz., a viz., the activity of various key N-assimilating enzymes and to delineate the indirect effect of low N on uptake and partitioning of other major macronutrients viz., P, K, S, which may indirectly regulate the N-use efficiency. A notable increase in sulfur, potassium, and phosphorus content was observed under nitrogen-deficient conditions. Varieties such as Carnamah and HD 2824 exhibit a significant increase in shoot phosphorus content, emphasizing their potential to optimize phosphorus acquisition and utilization efficiency under nutrient-limited conditions. The findings highlight the complex interplay between nutrient availability and plant responses, showcasing varietal-specific adaptations to nitrogen limitations.

Grain and shoot iron (Fe) content and root phytosiderophore release are the major determinants of Fe-deficiency tolerance index (FeDTI) and the reliable screening markers to breed Fe-efficient rice (Oryza sativa L.)

There is a need to exploit the genetic variability in rice to improve the Fe deficiency tolerance, particularly under aerobic conditions, and to improve the Fe uptake and accumulation in the grain to facilitate biofortification. The present research was conducted to ascertain the regulators and determinants of Fe-deficiency tolerance in rice. Fifty-seven diverse genotypes were investigated under Fe-deficient (1 µM, FDS, -Fe) and Fe-sufficient (100 µM, FSS, +Fe) nutrient solution cultures for growth and physiological attributes, Fe uptake and accumulation and root release of phytosiderophores (PS), etc., and Fe-deficiency tolerance index (FeDTI). A strong positive correlation was observed between root traits and the PS release. Further, a higher release of PS was evidenced as a major determinant of shoot Fe and grain Fe in rice particularly under Fe deficiency. Based on FeDTI, a total of ten rice genotypes were identified, and their Fe deficiency response was further validated on Fe deficient (∼2.1 ppm Fe, FeDS) and Fe-sufficient soils (∼10 ppm Fe, FeSS) in pot culture. Maintenance of high active Fe content and consequently a higher leaf chlorophyll content throughout the plant growth were extremely important determinants of grain yield and grain Fe fortification in rice under Fe deficiency than under the Fe sufficient condition. Based on the FeDTI, this study further identifies the Fe-deficiency tolerant rice genotypes which can be exploited through conventional and molecular breeding approaches to improve the Fe uptake efficiency and grain Fe content of the high-yielding rice genotypes.

Insights into the Fungicide Prothioconazole and Its Metabolite in Wheat: Residue Behavior and Risk Assessment

To clarify the residue formation of prothioconazole and its main metabolite in wheat plants, the uptake, translocation, and metabolism of prothioconazole in wheat roots and leaves were investigated by nutrient solution culture and the spraying method. The results showed that prothioconazole and its metabolites showed a trend of increasing and then decreasing in wheat plants under two treatment methods, and the concentration of prothioconazole and its metabolites was higher in the high-concentration group (5000 μg/mL) than in the low-concentration group (1000 μg/mL). The transferability from stem to leaf was stronger than that from root to stem. In the nutrient solution culture, prothioconazole and its metabolites were mainly enriched in wheat roots. The concentration of prothioconazole in wheat roots increases with the increase in prothioconazole concentration and was significantly higher than the prothioconazole concentration on stems and leaves. In wheat leaves in the spraying method, prothioconazole and its metabolites were conducted from leaves to stems and roots up to the nutrient solution. Prothioconazole-desthio was detectable in wheat nutrient solution, while prothioconazole was not detected. Analysis of actual samples of 9 wheat grains and 28 flours showed that the residues of prothioconazole and its metabolites met the maximum residue limit (0.1 mg/mL) set in China and by the Codex Alimentarius Commission. The results will provide a theoretical basis for the scientific use of prothioconazole and food security assurance.

Morphological traits and Zn content of several cassava genotypes in nutrient solution culture

Leaf morphological characters and nutrient content in leaf tissue can vary depending on plant genotype. The nutrient solution culture can produce leaves with good nutritional content. Therefore, this research aimed to evaluate and validate cassava putative mutants' morphological traits and Zn content using a nutrient solution culture system. This research was carried out from January to May 2022 at the greenhouse of Cikabayan Experimental Garden, IPB University, Bogor. This study used two cassava cultivars and ten mutant genotypes from the cassava research team of IPB University, resulting from mutation breeding by gamma irradiation. The plant characters observed in this study included the number of leaves, length and width of the leaflet, leaf colour, plant height, fresh and dry weight leaf, and analysis of Zn content. The data were analyzed using ANOVA at a significant level of α = 5%, followed by Tukey's further test. The results showed that the G2D1-422 genotype had a higher Zn content than the wild type (Ratim/G2) and the other genotypes. The high Zn genotypes (G2D1-422) and low Zn genotypes (Ratim (G2) had not significantly different in fresh and dry leaf weight. Meanwhile, the plant genotype did not affect other growth characteristics such as plant height, the number of leaves, and the length and width of the leaflets, and overall, the characters were similar between the observed genotypes.

Effects of Lead Pollution on Photosynthetic Characteristics and Chlorophyll Fluorescence Parameters of Different Populations of Miscanthus floridulus

This study was conducted in order to study the effect of different concentrations of lead pollution on the photosynthetic characteristics and growth of Miscanthus floridulus, and to reveal its photosynthetic adaptability to lead stress. The differences of gas exchange parameters, chlorophyll fluorescence characteristics and photosynthetic pigment of two Miscanthus floridulus populations, one population from Boluo an uncontaminated site, and another population from Dabaoshan, a mine site, were compared and studied through nutrient solution culture experiments treated with heavy metal lead (Pb) in green house. The results showed that (1) under Pb stress, the net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), intercellular carbon dioxide concentration (Ci), and chlorophyll content (Chl) of the leaves of the two populations decreased in different amplitude. Under moderate and severe Pb stress (80 mg·L−1, 120 mg·L−1, 240 mg·L−1), the plant biomass of non-mining population and mining population plants were 54.5%, 39.7%, 29.4% and 70.4%, 54.7%, 50.9% of the control, respectively. (2) Stomatal restriction was the main factor for the Pn’s decrease in the leaves of the non-mine population under light Pb stress, while the non-stomatal restriction was the main factor for Pn’s decrease in the leaves of the non-mine population under middle and high Pb stresses. (3) Under Pb stress, the maximum photochemical efficiency (Fv/Fm) and potential activity (Fv/Fo) of PS II reaction centers in the two populations of M. floridulus decreased. However, Fv/Fm and Fv/Fo showed a smaller decrease, but the capability to utilize light and the potential to activate PSII of the mine population remained higher than that of the non-mine population. The changes of photochemical quenching coefficient (qP) and non-photochemical quenching coefficient (NPQ) of PSⅡ showed that qP value decreased and NPQ value increased in the two populations under Pb stress. On the whole, the resistance mining area population had a low qP reduction and a large increase in NPQ. Electronic transfer rate (ETR) and PSII actual fluorescence efficiency (ΦPSII) of the mine population changed slightly under Pb stress. These results indicated that when under Pb stress, the electron transport activity and photosynthetic apparatus were damaged less in the mine population with high resistance than in the non-mine population with low resistance. Conclusion: the mining population of M. floridulus has strong tolerance to Pb, which is suitable for the pioneer species of gramineae in vegetation restoration construction in metal mining area.

Metabolomics Analysis Reveals Metabolites and Metabolic Pathways Involved in the Growth and Quality of Water Dropwort [Oenanthe javanica (Blume) DC.] under Nutrient Solution Culture.

Water dropwort (Oenanthe javanica (Blume) DC.) is an important vegetable crop. Nutrient liquid culture has become an important cultivation method in the production of water dropwort. However, the effects of different nutrient solution cultivation methods on the growth and quality of water dropwort remains unclear. In this study, to screen the most suitable nutrient solution formula for the cultivation of water dropwort, the effects of different nutrient solution formulas (Hoagland, Cooper, Dutch greenhouse, Garden-style, Yamasaki and SCAU) on plant physiological and quality characteristics are investigated. The plant height, root length, water content (%), distribution rate of dry matter (%), chlorophyll, VC, flavonoid, total phenolic, DPPH and dietary fiber of water dropwort under different nutrient solutions were determined. According to the analytic hierarchy process (AHP) of the growth index and quality index of water dropwort under different nutrient solutions, the Yamazaki nutrient solution was considered to be the most suitable nutrient solution formula for water dropwort. To further confirm the differences of water dropwort under nutrient solution culture and soil culture, the broadly targeted metabolomics were performed. A total of 485 metabolites were detected in water dropwort under optimal nutrient solution and soil cultivation. Metabolomics analysis showed that flavonoids were the most abundant differential accumulated metabolites, and most flavonoids were up-regulated. A qRT-PCR assay indicated that the structural genes of the flavonoid biosynthesis pathway (PAL, C4H, CHS, CHI, F3H, DFR, UFGT) were significantly higher under the Yamasaki nutrient solution treatment. The current study provided a theoretical basis and technical guidance for the nutrient solution cultivation of water dropwort. Meanwhile, this study provides new insights into the study of flavonoids in water dropwort.

Proteomic and Genomic Studies of Micronutrient Deficiency and Toxicity in Plants.

Micronutrients are essential for plants. Their growth, productivity and reproduction are directly influenced by the supply of micronutrients. Currently, there are eight trace elements considered to be essential for higher plants: Fe, Zn, Mn, Cu, Ni, B, Mo, and Cl. Possibly, other essential elements could be discovered because of recent advances in nutrient solution culture techniques and in the commercial availability of highly sensitive analytical instrumentation for elemental analysis. Much remains to be learned about the physiology of micronutrient absorption, translocation and deposition in plants, and about the functions they perform in plant growth and development. With the recent advancements in the proteomic and molecular biology tools, researchers have attempted to explore and address some of these questions. In this review, we summarize the current knowledge of micronutrients in plants and the proteomic/genomic approaches used to study plant nutrient deficiency and toxicity.

Mutation of OsPIN1b by CRISPR/Cas9 Reveals a Role for Auxin Transport in Modulating Rice Architecture and Root Gravitropism.

The distribution and content of auxin within plant tissues affect a variety of important growth and developmental processes. Polar auxin transport (PAT), mainly mediated by auxin influx and efflux transporters, plays a vital role in determining auxin maxima and gradients in plants. The auxin efflux carrier PIN-FORMED (PIN) family is one of the major protein families involved in PAT. Rice (Oryza sativa L.) genome possesses 12 OsPIN genes. However, the detailed functions of OsPIN genes involved in regulating the rice architecture and gravity response are less well understood. In the present study, OsPIN1b was disrupted by CRISPR/Cas9 technology, and its roles in modulating rice architecture and root gravitropism were investigated. Tissue-specific analysis showed that OsPIN1b was mainly expressed in roots, stems and sheaths at the seedling stage, and the transcript abundance was progressively decreased during the seedling stages. Expression of OsPIN1b could be quickly and greatly induced by NAA, indicating that OsPIN1b played a vital role in PAT. IAA homeostasis was disturbed in ospin1b mutants, as evidenced by the changed sensitivity of shoot and root to NAA and NPA treatment, respectively. Mutation of OsPIN1b resulted in pleiotropic phenotypes, including decreased growth of shoots and primary roots, reduced adventitious root number in rice seedlings, as well as shorter and narrower leaves, increased leaf angle, more tiller number and decreased plant height and panicle length at the late developmental stage. Moreover, ospin1b mutants displayed a curly root phenotype cultured with tap water regardless of lighting conditions, while nutrient solution culture could partially rescue the curly root phenotype in light and almost completely abolish this phenotype in darkness, indicating the involvement of the integration of light and nutrient signals in root gravitropism regulation. Additionally, amyloplast sedimentation was impaired in the peripheral tiers of the ospin1b root cap columella cell, while it was not the main contributor to the abnormal root gravitropism. These data suggest that OsPIN1b not only plays a vital role in regulating rice architecture but also functions in regulating root gravitropism by the integration of light and nutrient signals.

Antioxidant response of wheat to tire rubber ash and ZnO nanoparticles and ionic zinc exposure in nutrient solution culture

Antioxidant response of wheat to tire rubber ash and ZnO nanoparticles and ionic zinc exposure in nutrient solution culture

An Improved Technique for Isolation and Characterization of Single-Spore Isolates of Plasmodiophora brassicae.

Clubroot, caused by Plasmodiophora brassicae, is a soilborne disease that occurs in cruciferous crops worldwide. P. brassicae usually exists as a mixture of several pathotypes, which has hampered the research on resistance mechanisms of cruciferous crops against P. brassicae. In this study, clubroot galls were collected from a field in Shenyang, China, as a pathogen source to develop an efficient protocol for a single-spore isolation system of P. brassicae by optimizing the seedling age for inoculation, host inoculation method, and plant culture method. The operational steps of the single-spore isolation method were optimized as follows: the use of 2-day-old seedlings for inoculation, substituting a cryobox (100 × 2.0-ml vials) for culture dishes, the addition of nutrient solution culture, and microscopic observations of single spores. The rate of infection success was substantially improved, and single-spore isolates of four pathotypes (4, 8, 9, and 11) were acquired in this system. Subsequently, the optimized system was used to isolate and characterize the pathotypes of single-spore isolates of P. brassicae collected from five fields in regions in China. Approximately four to nine pathotypes were isolated from each region. Among these, pathotype 4 was the most prevalent. This study provides a source of valuable information that can eventually be used for the genetic analysis of host-P. brassicae interaction.

Antibiotic Resistance Gene Transformation and Ultrastructural Alterations of Lettuce (Lactuca sativa L.) Resulting from Sulfadiazine Accumulation in Culture Solution

The research herein explored the possible mechanism of toxicity of the antibiotic sulfadiazine (SD) and the related antibiotic resistance gene transformation in lettuce by systematically investigating its growth responses, ultrastructural changes, and antibiotic resistance gene transformation via solution culture experiments. The results showed that SD mainly accumulated in the roots of lettuce at concentrations ranging from 6.48 to 120.87 μg/kg, which were significantly higher than those in leaves (3.90 to 16.74 μg/kg). Lower concentrations of SD (0.5 and 2.0 mg/L) in the culture nutrient solution exerted little effect on lettuce growth, while at SD concentrations higher than 10 mg/L, the growth of lettuce was significantly inhibited, manifesting as shorter root length and lower dry matter yield of whole lettuce plants. Compared with that for the control group, the absolute abundance of bacteria in the root endophyte, rhizosphere, and phyllosphere communities under different concentrations of SD treatment decreased significantly. sul1 and sul2 mainly accumulated in the root endophyte community, at levels significantly higher than those in the leaf endophyte community. Studies of electrolyte leakage and ultrastructural characteristics of root and leaf cells indicated that lettuce grown in culture solutions with high SD concentrations suffered severe damage and disintegration of the cell walls of organs, especially chloroplasts, in leaves. Furthermore, the possible mechanism of SD toxicity in lettuce was confirmed to start with the roots, followed by a free flow of SD into the leaves to destroy the chloroplasts in the leaf cells, which ultimately reduced photosynthesis and decreased plant growth. Studies have shown that antibiotic residues have negative effects on the growth of lettuce and highlight a potential risk of the development and spread of antibiotic resistance in vegetable endophyte systems.

The expression of OsPLA2-III and OsPPO genes in rice (Oryza sativa L.) under Fe toxicity stress

Lipids are an important biomolecule in plants because of their structural and functional roles in plant cells. Moreover, they could act as signal molecules in the defense system of plants suffering from biotic and abiotic stresses. Furthermore, plants develop various tolerance strategies to cope with iron (Fe) toxicity, for example, by involving genes in the detoxification process and other mechanisms. Therefore, the objective of this research was to investigate the expression of OsPLA2-III and OsPPO genes during Fe stress conditions. It was carried out using two-week-old seedlings of two rice varieties, namely, IR64 (Fe-sensitive variety) and Pokkali (Fe-tolerant variety). The seedlings were treated with 400 ppm FeSO4.7H2O in the nutrient culture solution and compared with control that received 1 ppm FeSO4.7H2O. Furthermore, leaf bronzing, chlorophyll content and relative expression of OsPLA2-III and OsPPO genes were observed. An in-silico study was also performed to predict the interaction between OsPLA2-III and OsPPO proteins. The results showed that the Fe toxicity induced leaf bronzing, decreased leaf chlorophyll content, and increased the expression levels of OsPLA2-III and OsPPO genes. Therefore, both genes were suggested to have a role in plant tolerance mechanism during Fe toxicity stress through the lipid signaling pathway.

The Effectiveness of Nutrient Culture Solutions with Agar Addition as An Evaluation Media of Rice Under Iron Toxicity Conditions

Background: Evaluation of the tolerance level of rice to iron (Fe) toxicity stress can be done using a hydroponic system in a nutrient culture solution under a controlled condition. This study aimed to obtain a nutrient culture solution that effective as a medium for evaluating the response of rice under Fe toxicity stress condition. Methods: This experiment was carried out by comparing the effectiveness of three kinds of nutrient culture media, namely Yoshida’s Half-Strength solution (HSY), Yoshida’s Half-Strength + 0.2% agar solution (HSYA), and Yoshida’s Full-Strength + 0.2% agar solution (FSYA) using two rice genotypes, Inpara 5 (sensitive to Fe toxicity) and Mahsuri (tolerant to Fe toxicity). Leaf bronzing level, plant dry weight, and pH of nutrient culture media were observed in this experiment. Results: The results showed that the stress response as represented by the bronzing score in Inpara 5 leaves was known to be higher than that of Mahsuri in the three nutrient culture media. The decrease of root and shoot dry weight in Inpara 5 was higher than that of Mahsuri. In addition, the decrease in the pH of nutrient culture solution media without an agar addition (HSY) occurred faster than the media with the agar addition (HSYA and FSYA). Conclusion: The HSYA and FSYA media exhibited a similar pattern of pH declining but causing significant differences in growth responses between Inpara 5 and Mashuri indicating the HSYA medium is considered more efficient compared to the FSYA medium because it only requires a smaller amount of agar.

Effects of Nutrient Solution Concentration, Cultivars, and Culture Methods on Leaf Resistance of Tomato Plant

Effects of Nutrient Solution Concentration, Cultivars, and Culture Methods on Leaf Resistance of Tomato Plant

Tolerance of 20 heirloom rice varieties at seedling stage salinity stressed and their growth in lowland coastal area

Coastal area of Bengkulu Province is home of many heirloom rice varieties and play an important role in contributing rice production in the province. However, as the climate change proceeds, a progressive sea water inundation has increased soil salinity mainly in low-lying areas and jeopardizing the sustainability of rice production in coastal regions. The use of salt-tolerant varieties, therefore, would be a sensible solution to alleviate the adverse effect of soil salinity in respect of maintaining the crop production in the coastal areas. The objective of this study was to examine the salinity tolerance of 20 heirloom rice varieties collected from a coastal area of Bengkulu Province. Prior to the screening process, lethal concentration 90 (LC90) was determined by assaying the seedlings of ‘Kuning Tinggi’ in a series of nutrient solution containing a different concentration of NaCl (0, 2000, 4000, 6000, 8000 and 10000 ppm). Using a regression analysis, LC90 was detected at a concentration of 3910 ppm. The screening was performed by exposing the varieties in the nutrient solution culture containing 4000 ppm NaCl and growing them on the tidal swamp. Under nutrient culture evaluation, the symptom of NaCl toxicity was scored and converted to salinity tolerance index. ‘Humbur’, ‘Kuning Tinggi’ and ‘Padang Bakung’ exhibited medium tolerant, while ‘Beram’, ‘Imperata’ and ‘Kuning’ exhibited very sensitive. Further evaluation of the tidal swamp for vegetative and generative performances signified that ‘Humbur’ and ‘Kuning Tinggi’ had medium tolerant to salinity stress

Differential Regulation of Kernel Set and Potential Kernel Weight by Nitrogen Supply and Carbohydrate Availability in Maize Genotypes Contrasting in Nitrogen Use Efficiency.

Sub-optimal nitrogen (N) conditions reduce maize yield due to a decrease in two sink components: kernel set and potential kernel weight. Both components are established during the lag phase, suggesting that they could compete for resources during this critical period. However, whether this competition occurs or whether different genotypic strategies exist to optimize photoassimilate use during the lag phase is not clear and requires further investigation. We have addressed this knowledge gap by conducting a nutrient solution culture experiment that allows abrupt changes in N level and light intensity during the lag phase. We investigated plant growth, dry matter partitioning, non-structural carbohydrate concentration, N concentration, and 15N distribution (applied 4 days before silking) in plant organs at the beginning and the end of the lag phase in two maize hybrids that differ in grain yield under N-limited conditions: one is a nitrogen-use-efficient (EFFI) genotype and the other is a control (GREEN) genotype that does not display high N use efficiency. We found that the two genotypes used different mechanisms to regulate kernel set. The GREEN genotype showed a reduction in kernel set associated with reduced dry matter allocation to the ear during the lag phase, indicating that the reduced kernel set under N-limited conditions was related to sink restrictions. This idea was supported by a negative correlation between kernel set and sucrose/total sugar ratios in the kernels, indicating that the capacity for sucrose cleavage might be a key factor defining kernel set in the GREEN genotype. By contrast, the kernel set of the EFFI genotype was not correlated with dry matter allocation to the ear or to a higher capacity for sucrose cleavage; rather, it showed a relationship with the different EFFI ear morphology with bigger kernels at the apex of the ear than in the GREEN genotype. The potential kernel weight was independent of carbohydrate availability but was related to the N flux per kernel in both genotypes. In conclusion, kernel set and potential kernel weight are regulated independently, suggesting the possibility of simultaneously increasing both sink components in maize.

Effect of Landfill Leachate on the Growth Parameters in Two Selected Varieties of Fiber Hemp

The influence of landfill leachate on selected growth parameters in two varieties (‘Bialobrzeskie’ and ‘Monoica’) of hemp (Cannabis sativa L.) was studied to evaluate phytoremediation potential of these varieties. The plants were cultivated in hydroponic culture in Knop's nutrient solution. Landfill leachate was added to nutrient solution in concentrations of 10, 15, 20 and 40%, respectively. After 14 days of cultivation, selected parameters of above-ground organs and root system were determined in experimental plants, namely height of plants, dry weight of aerial parts, total leaf area, total length of the root system, dry weight of the root system and the content of photosynthetic pigments in leaves. The leachate application affected all the monitored parameters: the decrease in height of the plants, length of the root system, dry weight, total leaf area, and content of photosynthetic pigments were observed. While the 10% and 15% concentration of leachate often caused only a slight decrease in the monitored parameters, the 20% concentration dramatically affected all the observed characteristics. Concentration of 40% caused severe stunting and in some cases, even dying of experimental plants. The higher degree of tolerance in almost all parameters was observed in ‘Monoica’. This variety appears to be more suitable for landfill leachate treatment, but further research is needed, especially in terms of heavy metals accumulation in individual organs. According to our knowledge, this paper represents the first study on the use of hemp for treatment of landfill leachate.

Interactions between cadmium and zinc in uptake, accumulation and bioavailability for Salix integra with respect to phytoremediation

The willow (Salix spp.) is a potential accumulator of cadmium (Cd)/zinc (Zn), and the interaction between Cd and Zn is an important factor influencing their phytoextraction potentials. In this study, interactions between Cd and Zn in uptake, accumulation and bioavailability for Salix integra clone SI63 were investigated through nutrient solution and soil culture methods. The result of the soil culture showed that Cd had additive effects for Zn-caused biomass reduction. The result from nutrient solution indicated that added Zn showed antagonistic (low Cd level) or synergistic (moderate and high Cd levels) effects on shoot Cd accumulation and antagonistic effects on root Cd accumulation. Irrespective of nutrient solution or soil culture experiment, Cd addition always had antagonistic effects on Zn accumulation in both shoots and roots. Under Cd10Zn50 condition, the clone accumulated higher Cd and Zn concentrations (95 μg g−1 Cd and 165 μg g−1 Zn) in shoots. Cd slightly increased bioavailable Zn in the rhizosphere, and EDTA well predicted bioavailable Cd and Zn in the rhizosphere. Interactions of Cd–Zn markedly changed their respective phytoextraction potentials, especially for Zn. This result will provide a new insight into improving phytoextraction potentials of both Cd and Zn using willows through applying metal interactions.

Identification of phosphorus efficient rice cultivars under low P nutrition through hydroponic based screening

Phosphorus (P) is one of the major nutrients required by plants. A higher portion of P in lowland rice soils is found in unavailable forms due to fixation. Therefore, continuous application of P fertilizer to rice (Oryza sativa L.) is needed to obtain a satisfactory yield. Identification and subsequent cultivation of high yielding rice varieties which can withstand low level of P is a better alternative to the continuous P application. The objective of this study was to categorize Sri Lankan rice varieties according to their response to P deficient conditions. Forty eight rice varieties including three old improved varieties and 45 new improved varieties were evaluated at deprived (10 μM P) and sufficient (50 μM P) P levels in a nutrient solution culture. Multiple plant traits; number of tillers, root and shoot dry weights and P content in shoot tissues were assessed at 52 days after planting. Rice variety Bg 94-1 gained higher biomass and P uptake (i.e. shoot P content- mg/plant). Simultaneously, At402 had lower biomass gain and shoot P content. Rice varieties were grouped into two distinct clusters based on their responses to P deficiency such as biomass gain, P uptake and number of tillers per plant. This study showed that At 405, Bg 94-1, At 307, Bg 304, Bg 300 and At 354 are promising rice varieties with higher response to low level of P supply.

Tolerance and recovery of the annual pasture legumes Melilotus siculus, Trifolium michelianum and Medicago polymorpha to soil salinity, soil waterlogging and the combination of these stresses

This study evaluated the responses to and recovery from soil waterlogging, soil salinity and the combination of these stresses of the annual pasture legumes Melilotus siculus cv. Neptune, Trifolium michelianum cv. Frontier and Medicago polymorpha cv. Scimitar. The major aim was to test the tolerance of these plants to salinity and waterlogging in soil inoculated with rhizobia, adding to previous controlled-environment studies, which have used nutrient solution cultures, as well as to examine post-stress recovery. Plants were grown in pots of soil inoculated with their appropriate species-specific rhizobia. Drained non-saline controls, and waterlogged non-saline, drained saline (100 mM NaCl) and waterlogged saline treatments were imposed for 3 weeks, followed by a 4 week recovery period. In the waterlogged saline soil, shoot dry mass of M. siculus was 63% of the control, compared to 10% for T. michelianum and 5% for M. polymorpha, and after the recovery phase was 75% of the control for M. siculus, 58% for T. michelianum and 4% for M. polymorpha. Foliar Na+ concentrations of T. michelianum and M. polymorpha were 2.8-fold higher than for M. siculus. The greater tolerance of M. siculus can be attributed to regulation of leaf Na+ concentrations in saline conditions and the formation of aerenchymatous phellem to enhance O2 supply to roots in waterlogged soils. This controlled glasshouse study using pots of soil supports earlier nutrient solution experiments and field observations that M. siculus possesses greater tolerance of combined waterlogging and salinity, than T. michelianum and M. polymorpha.