Improvement of wheat (Triticum aestivum) drought tolerance by seed priming with silicon

Silicon has the potential to improve drought tolerance in crops. Seeds primed with silicon were used in the present study to explore its potential benefit to withstand water stress. Seeds of two wheat varieties, NARC-2009 and Chakwal-50, were sown in pots after priming with distilled water and different concentrations (0.5%, 1.0% and 1.5%) of silicon sources (silicic acid, sodium silicate and silica gel) at PMAS, Arid Agriculture University, Rawalpindi. Maximum silicon uptake at three-leaf stage (0.028 µg g^?1 dry weight (DW)), anthesis (0.072 µg g^?1 DW) and maturity (0.103 µg g^?1 DW) was recorded for silica gel. Silicon uptake increased significantly in response to increase in Si concentration from 0.5% to 1.5%. Leaf membrane stability index, epicuticular wax, relative water content and proline remained maximum – 78.90%, 2.6 mg g^?1 DW, 83.88% and 54.90 µg g^?1 – for silica gel treatments compared with others. Silica gel with 1.5% silicon concentration resulted in maximum spike length (14.3 cm), biological yield (7.63 g pot^?1), hundred-grain weight (3.97 g pot^?1) and grain yield (2.46 g pot^?1). Based on the study outcomes, it is concluded that silica gel might be a good priming option with 1.5% silicon concentration to establish plant under drought stress.     

The Physiology and Biochemical Tolerance of Cabbage to Se (VI) Addition to the Soil and by Foliar Spraying

The effects of selenium (Se) (VI) soil fertilization with 2 μg Se L^?1 or foliar spraying twice with 20 mg Se L^?1 in the form of sodium (Na) selenate on the physiological and biochemical characteristics of cabbage plants were studied. The ability of the plants to take up Se and translocate it to different parts of the plants was also studied. Despite the high concentration of Se in the foliar solution, there was no effect on photosynthesis, transpiration rate, photochemical efficiency of PSII, or electron transport system activity. The amount of chlorophyll and anthocyanins were unchanged. At harvest, the concentration of Se in control plants was lower than 100 ng Se g^?1 dry weight (DW), while plants treated with 20 mg Se L^?1 contained 5500 ng Se g^?1. Selenium enriched cabbage could be used in human nutrition. The tolerance of cabbage to Se could be explained by the formation of insoluble compounds that are not available for the plant.     

Growth Response and Selenium and Boron Distribution in Broccoli Varieties Irrigated with Poor Quality Water

Abstract

Selenium (Se), and boron (B), and salinity contamination of agricultural drainage water is potentially hazardous for water reuse strategies in central California. This greenhouse study assessed tolerance and Se, B, and chloride (Cl^?) accumulation in different varieties (Emerald City, Samurai, Greenbelt, Marathon) of broccoli (Brassica oleracea L.) irrigated with water of the following different qualities: (1) non‐saline [electrical conductivity (EC) of <1 dS m^?1]; (2) Cl^?/sulfate salinity of ～5 dS m^?1, 250 µg Se L^?1, and 5 mg B L^?1; and (3) non‐saline and 250 µg Se L^?1. One hundred and ten days after transplanting, plants were harvested and dry weight (DW) yields and plant accumulation of Se, B, and Cl^? was evaluated in floret, leaf, and stem. Irrespective of treatments floret yields from var. Samurai were the lowest among all varieties, while floret yields from var. Marathon was the only variety to exhibit some sensitivity to treatments. For all varieties, plant Se concentrations were greatest in the floret (up to 51 mg kg^?1 DW) irrespective of treatment, and B and Cl^? concentrations were greatest in the leaves; 110 mg B kg^?1 DW and 5.4% Cl^?, respectively. At post harvest, treatment 2 (with salinity, B, and Se) increased soil salinity to almost 6 dS m^?1, total Se concentrations to a high of 0.64 mg kg^?1 DW soil, and water soluble B concentrations to a high of 2.3 mg B L^?1; soluble Se concentrations were insignificant. The results indicate that var. Emerald City, Greenbelt, and Marathon should be considered as recipients of moderately saline effluent enriched with Se and B under field conditions.     

LIMESTONE PARTICLE SIZE AND RESIDUAL LIME CONCENTRATION AFFECT PH BUFFERING IN CONTAINER SUBSTRATES

The objective was to quantify how the concentration and particle size of unreacted “residual” limestone affected pH buffering capacity for ten commercial and nine research container substrates that varied in residual calcium carbonate equivalents (CCE) from 0.3 to 4.9 g CCE·L^?1. The nine research substrates contained 70% peat:30% perlite (by volume) with dolomitic hydrated lime at 2.1 g·L^?1, followed by incorporation of one of four particle size fractions [850 to 2000 μm (10 to 20 US mesh), 250 to 850 μm (20 to 60 US mesh), 150 to 250 μm (60 to 100 US mesh), or 75 to 150 μm (100 to 200 US mesh)] of a dolomitic carbonate limestone at 0, 1.5 or 3.0 g·L^?1. Substrate-pH buffering was quantified by measuring the pH change following either (a) mineral acid drenches without plants, or (b) a greenhouse experiment where an ammonium-based (acidic) or nitrate-based (basic) fertilizer was applied to Impatiens wallerana Hook. F. Increasing residual CCE in commercial substrates was correlated with greater pH buffering following either the hydrochloric acid (HCl) drench or impatiens growth with an ammonium-based fertilizer. Research substrates with high applied lime rate (3.0 kg·m^?3) had greater pH buffering than at 0 or 1.5 g·L^?1. At 3 g·L^?1, the intermediate limestone particle size fractions of 250 to 850 μm and 150 to 250 (20 to 60 or 60 to 100 US mesh) provided the greatest pH-buffering with impatiens. Particle fractions finer than 150 μm reacted quickly over time, whereas buffering by particles coarser than 850 μm was limited because of the excessively slow reaction rate during the experimental periods. Addition of acid from either an ammonium-based fertilizer or HCl reduced residual CCE over time. Dosage with 40 meq acid from HCl per liter of substrate or titration with HCl acid to substrate-pH of 4.5 were well-correlated with pH buffering in the greenhouse trials and may be useful laboratory protocols to compare pH buffering of substrates. With nitrate fertilizer application, residual CCE did not affect buffering against increasing pH. Residual limestone is an important substrate property that should be considered for pH management in greenhouse crop production under acidic conditions.     

Methods to evaluate pesticide damage to the biomass of the soil microflora

Respiratory methods to estimate the amount of C in the soil microbial biomass and the relative contributions of procaryotes and eucaryotes to the biomass were used to evaluate the influence of pesticides on the soil microflora. Experiments were conducted with 5 and 50 μg·g^?1 of three fungicides, captan, thiram and verdasan. At 5 μg·g^?1 they caused significant decreases (40%) in the biomass; the organomercury fungicide verdasan also caused a shift from fungal to bacterial dominance. Within 8 days, biomass in captan- and thiram-amended soils had recovered to that of the controls. Although the fungal to bacterial balance was restored in verdasan-amended soils, biomass recovery was not complete. At 50 μg·g^?1 the fungicides caused long-term decreases in the biomass and altered the relative proportions of the bacterial and fungal populations. Verdasan had the greatest effect on soil microbial biomass and composition.     

Effect of Treated Wood on Biosolids Composting

The possibility of using construction and demolition (C&;D) waste wood as a bulking material in biosolids composting was investigated. Potential contaminants in C&;D waste wood include arsenic (As), chromium (Cr), and copper (Cu) from treated wood, and lead (Pb) from paints. Untreated and treated woodchips from C&;D wood were mixed with biosolids, composted using an aerated static pile process, and cured. There were no significant differences between untreated and treated woodchips with respect to composting process, time to stability, or product quality. Composting parameters monitored included moisture content, pH, electrical conductivity, organic matter degradation, fecal coliform levels, and stability by respirometry. Finished compost quality was evaluated in terms of potential toxic elements (PTE) levels. PTE values in treated woodchips (26 ± 35, 29 ± 41, 56 ± 46, and 5 ± 5 µg·g^?1 for As, Cr, Cu, and Pb, respectively) were higher and more variable than those in the untreated woodchips (3 ± 3, 17 ± 8, 13 ± 2, and 0.5 ± 0.0 µg·g^?1). However, both untreated and treated wood compost products met Canadian Council of Ministers of the Environment Category B values for PTE. In addition, and only molybdenum (Mo) and Cu exceeded Category A thresholds. Biosolids were the most significant contributor of Mo, while Cu contributions came from both biosolids and wood chips; some samples of pressure-treated wood showed concentrations of Cu in the range of 765 to 8,455 µg·g^?1. The results of this study suggest that treated wood from C&;D recycling facilities will not significantly degrade the quality of biosolids compost products.     

Nitrification mineralisation and inorganic-N uptakein evergreen forests of the central Himalayas

Nitrogen mineralisation and available nitrogen (NO₃^– + NH₄⁺) in two evergreen forests species, viz. Quercus leucotrichophora and Pinus roxburghii, were examined. The plant available N ranged from 7.7–35.8 μg·g^–1·m^–1 with maximum values in March and minimum in November. The trend for N-mineralisation was opposite to that of the size of the available N-pool. N-Mineralisation rates ranged from 1.7–30.3 μg·g^–1·m^–1 within an annual cycle. Inorganic-N uptake was calculated for each incubated period, and for an entire year showed that in an oak forest site, nitrate-N was the dominant form of mineral nitrogen taken up by plants from soil. However, in a chir pine forest, nitrate-N and ammonium-N are equally taken up by plants from the soil. In both oak and pine forest sites, the nitrate-N uptake was maximum in the month of July and ranged between 2.4–11 μg·g^–1·m^–1 in the pine forest site and from 0–25 μg·g^–1·m^–1 in the oak forest site. In addition, ammonium-N varied from 0–12 μg·g^–1·m^–1 in the pine forest site and from 1–20 μg·g^–1·m^–1 in the oak forest site. N-Mineralisation was greater in N-rich forests and was moisture (soil) dependent and inversely related to bulk density.     

Reduced trigonelline accumulation due to rhizobial activity improves grain yield in peanut (Arachis hypogaea L.)

Abstract

Crop improvement for drought tolerance is critical for the future of crop production. The objectives were to examine the relationship between trigonelline (TRG) accumulation and yield traits in 10 peanut (Arachis hypogaea L.) genotypes inoculated with two commonly used nitrogen-fixing Rhizobium spp., and to evaluate a role of TRG on growth traits. TRG increased as a defensive metabolite in response to water deficit, but resulted in the reduction of the number of nodules and yield. Symbiotic rhizobial activity helped plants to improve yield particularly in a fully irrigated field rather than under reduced irrigation. TRG concentrations in genotypes (7 out of 10) increased under reduced irrigation as compared with those under full irrigation in two years. Mean number of nodules at maturity (120 days after planting) across genotypes under reduced irrigation were 89 in the control, 111 in Lift, and 161 in Histick treatments, among which Histick was significant (p < 0.05) for nodulation. Mean pod yields in the control, Histick, and Lift treatments were 1.69, 2.34 and 1.87 Mg ha^-1, respectively, under reduced irrigation. Under full irrigation, pod yields were 3.35 in the control, 4.50 in Histick and 3.41 Mg ha^-1 in Lift treatments, but were more significantly improved as treated with Histick than other treatments. Genotype ICGS-76 produced the highest pod yield (5.13 Mg ha^-1) as treated with Histick. All genotypes treated with Histick and Lift biosynthesized less TRG (decreased from 5.8 to 65.3% relative to the control) but produced larger numbers of pods (increased from 9.2 to 80.4% relative to the control), which resulted in substantially higher pod yields.     

Phosphorus Efficiency of Buckwheat (Fagopyrum esculentum)

The ability of buckwheat (Fagopyrum esculentum) roots to acquire phosphorus (P) was characterized by investigating P uptake, morphological features, and chemical changes in the rhizosphere. Over a range of nutrient solution P concentrations (5–500 μmol · L^?1), maximum shoot growth was achieved with a P supply between 5 and 100 μmol · L^?1. Root weight and root length, as well as length and frequency of root hairs, were higher at low P levels. Root surface and the root surface/shoot dry weight ratio reached high values. Though P uptake rates were only moderate (0.15 pmol · cm^?1 root · sec^?1), shoot P concentrations were high (1.8% of dry weight with 100 μM P) predominantly being inorganic (80%). Phosphorus efficiency was characterized by a high specific absorption rate (810 mmol P · kg^?1 root dry wt · d^?1) rather than by an efficient utilization for dry weight production. Root exudates of low-P plants had lower pH values than exudates of high-P plants and increased the solubility of FePO₄ and MnO₂ to a greater extent. Amounts of exuded organic acids and phenolics were low and could not account for the observed solubilization of FePO₄ and MnO₂. Enhanced hydrolysis of glucose-6-phosphate by exudates from low-P plants was due to an increased “soluble” acid phosphatase activity, and root surface phosphatase activity was also slightly enhanced with P deficiency. In the rhizosphere soil of buckwheat, some depletion of organic P forms was observed, and in pot trials with quartz sand, buckwheat utilized glucose- 6-phosphate as a P source at the same rate as inorganic P.     

Effects of pentachlorophenol on asymbiotic nitrogen fixation in soil

The effect of 50, 100, 150, and 400 μg sodium pentachlorophenate (Na-PCP) per gram soil was studied in nonsterile soil incubated under aerobic and anaerobic conditions, and in sterilized soil inoculated withAzotobacter sp. isolated from the soil. N₂ fixation was determined by acetylene reduction. Pentachlorophenate at a concentration of 50 μg g^?1 had an inhibitory effect in nonsterile soil incubated aerobically while strong inhibition of dinitrogen fixation in nonsterile soil occurred in the presence of 100 μg g^?1 and above. The EC₅₀ values for the inhibition of nitrogenase activity in nonsterile soil incubated aerobically and anaerobically and in sterilized soil inoculated withAzotobacter sp. suspensions were 49.8±1.4 μg Na-PCP g^?1, 186.8±2.8 μg Na-PCP g^?1, and 660.8±29.3 μg Na-PCP g^?1, respectively.     

Toxicity of heavy metals (Zn,Cu, Cd,Pb) to vascular plants

The literature on heavy metal toxicity to vascular plants is reviewed. Special attention is given to forest plant species, especially trees, and effects at low metal concentrations, including growth, physiological, biochemical and cytological responses. Interactions between the metals in toxicity are considered and the role of mycorrhizal infection as well. Of the metals reviewed, Zn is the least toxic. Generally plant growth is affected at 1000 μg Zn L^?1 or more in a nutrient solution, though 100 to 200 µg L^?1 may give cytological disorders. At concentrations of 100 to 200 μg L^?1, Cu and Cd disturb metabolic processes and growth, whereas the phytotoxicity of Pb generally is lower. Although a great variation between plant species, critical leaf tissue concentrations affecting growth in most species being 200 to 300 μg Zn g^?1 dry weight, 15 to 20 μg Cu g^?1 and 8–12 μg Cd g^?1. With our present knowledge it is difficult to propose a limit for toxic concentrations of Zn, Cu, Cd and Pb in soils. Besides time of exposure, the degree of toxicity is influenced by biological availability of the metals and interactions with other metals in the soil, nutritional status, age and mycorrhizal infection of the plant.     

The fate of mercury in coal-fired power plants and the influence of wet flue-gas desulphurization

The Hg concentrations in coal as fired in power plants in the Netherlands are low, 0.2 mg·kg^?1 on average. After combustion the Hg is released partly (between 1 and 98%, on average 42%) in a gaseous phase, which is finally emitted into the air. The other part of the Hg, which remains in the ash is separated from the flue gases by electrostatic precipitators. The variation of the vaporisation percentage of Hg is probably caused by the presence of two chemical forms: Hg^o and HgCl₂. This may be concluded from the observation that relatively high concentrations of HCl in the flue gases (≈150 mg·m^?3) give rise to low Hg concentration in the vapor phase. In cases when the concentrations of HCl are relatively low (≈25 mg·m^?3) the amount of Hg in the vapor phase is high. The average gas phase concentrations of Hg in the flue gases, based on 33 measurements with no FGD, is 4.1 μg·m_fo ^?3. In a wet FGD based on the lime/limestone-gypsum process 50 to 70% of the Hg in the flue gases is removed, leaving a residual concentration of 1–2 μg·m_fo ^?3. The emission factor is then about 0.5 mg·GJ^?1 or 5 μg·kWhr^?1. In one particular measuring serie the fate of Hg was studied in a FGD-installation with a prescrubber.     

An input/output flux for lead in a coastal bay off Alexandria region

During 1987, seawater, rain, dust and drainage water samples were collected from Abu-kir bay (360 km²) east of Alexandria city to set up and evaluate the relative importance of different sources to the biogeochemical cycle of Pb in the bay. The mean total concentration of Pb in the bay water was 455 ± 180 and 785 ± 287 ng kg^?1 during low and high flow periods, respectively. About 75 ±12% are in the particulate form. The bay receives annually about 8.12 ± 2.18 and 6.13 ± 1.06 ± of Pb through agricultural and industrial discharge. In addition, 0.48 ± 0.11 ± yr^?1 and 0.23 ± 0.04 t yr^?1 of Pb reaches the bay through wet and dry depositions, respectively. The outflowing surface water from the bay carries 15.4 ± 3.6 t Pb yr^?1 to the southeastern Mediterranean waters. Data from sedimentation traps indicated that the bulk sedimentation rate in the bay was 95 ± 18 kg yr^?1 elevating the concentrations of Pb in sediments to more than 64 μg g^?1. The imbalance in the Pb flux (excess + 0.6 ± 0.08 t) indicates Pb accumulation in the water column. The apparent residence time of Pb in the bay is 62 ± 15 d. The assimilative capacity of Pb in the bay expressed in terms of Pb loading / in bay concentration amounted to 25 ± yr^?1/ μg L^?1. A 10% reduction in the present day load to the bay will yield a Pb concentration of less than 0.1 μg kg^?1 after 11 to 12 yr.     

PHYSIOLOGICAL AND BIOCHEMICAL CHANGES IN CATHARANTHUS ROSEUS L. IN RESPONSE TO BORON NUTRITION

Catharanthus roseus L., a medicinally important plant was grown till maturity at varying levels of boron (0.033, 0.066, 0.33 and 3.3 mg B L^?1) supply. Optimum yield was observed in plants receiving 0.33 mg B L^?1. Plants receiving deficient boron showed growth reduction and visual symptoms such as chlorosis and cupping of young emerging leaves and apical tip necrosis. The number and size of the flowers, pods and seeds formed and the pollen viability of the boron deficient plants was markedly reduced. The threshold values for deficiency and toxicity were 57 and 79 μg B g^?1 dry weight for vegetative growth and 60.4 and 68.9 μg B g^?1 dry weight for reproductive growth, respectively, and is reported for the first time in periwinkle. An increase was observed in reducing and non-reducing sugars and in activity of acid phosphatase and ribonuclease in boron stressed plants.     

Effect of pH on the bioaccumulation of low level,dissolved methylmercury by rainbow trout (Oncorhynchus mykiss)

An inverse relationship has been observed between pH and McHg concentration in freshwater fish. Many hypotheses exist regarding the mechanisms which lead to elevated levels of organic Hg in fish from low pH lakes. To determine if pH has a direct effect on the rate of McHg bioaccumulation in fish, rainbow trout fingerlings (Oncorhynchus mykiss) were exposed to a low concentration of aqueous methylmercuric chloride (1.38 ± 0.49 ng·L^?1) at four pH-levels (8.2, 7.0, 6.3, 5.8) for eight weeks. McHg and total Hg were specifically determined on whole fish homogenates and water samples. The pH was found to have a significant: inverse effect on the rate of McHg bioaccumulation in the fish only in the lowest exposure level. Fish held at pH 5.8 had an uptake rate of 1.11 ± 0.07 ng·g^?1·d^?1, while those at pH ≥ 6.3 had a MeHg tissue uptake rate of ≤ 0.64 ± 0.07 ng·g^?1·d^?1. Total body burden of MeHg in the fish held at pH 5.8 also showed an elevated level of MeHg when compared with fish held at higher pH-levels, but the difference was less dramatic. These results suggest that a portion of the Hg burden in fish from low pH systems may be due to the direct effects of low pH on bioaccumulation, but that a threshold may exist above which pH does not play a significant role.     

LEAF NUTRIENT CONTENT AND TOMATO FRUIT YIELD AS AFFECTED BY SINGLE SUPER PHOSPHATE RATES APPLIED BY DRIP IRRIGATION

A drip fertigation system should use low-cost phosphorus fertilizer available in small markets to smallholders such as especially Brazilian tomato growers. A study was conducted in an unheated greenhouse to establish an optimum rate of single superphosphate (SS) to formulate an aqueous solution that can be applied to tomato plants through a low-pressure drip irrigation system. Five rates of SS [18% phosphorus pentoxide (P₂O₅)] 0, 25, 50, 100, and 200 g·plant^?1, were evaluated in a randomized block design with four replications. Each rate was subdivided into 15 equal parts. Each part was dissolved in water (210 mL for each plant) and the mixture left to settle for 24 hours. The supernatant was applied by drip irrigation every week for 15 weeks. The tomato plants were grown in 9 dm³ plastic bags containing fertilized substrate in an unheated greenhouse. The leaf contents of nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), copper (Cu), and zinc (Zn) were not affected by the treatments. The highest phosphorus (P), manganese (Mn), and iron (Fe) leaf contents were obtained from plants fertilized with SS at 79; 0; 0 g·plant^?1, respectively. The marketable tomato fruit yield, measured up to 123 days after transplanting, increased with the increasing SS up to 54 g·plant^?1, resulting in a yield of 6.16 kg·plant^?1, corresponding to 10.3 kg·m^?2. A settled aqueous solution of SS (54 g·210 mL^?1 of water) can be applied weekly to tomato plant through a low-pressure drip irrigation system during the plant cycle.     

Impact of Pseudomonads and Ethylene on the Cadmium and Nickel Rhizofiltration of Sunflower,Squash, and Indian Mustard

Three hydroponic experiments were set up to study the rhizofiltration of cadmium (Cd) or nickel (Ni) from artificially contaminated nutrient solution with sunflower, squash, or Indian mustard. After 48 h of exposure with 2 mg L^?1 Cd‐contaminated water, 460, 415, or 1092 µg Cd g^?1 (dry weight) was detected in roots of 33‐day‐old sunflower and squash or in 50‐day‐old Indian mustard, respectively. As calculated, 1 g of root dry matter of the tested crop species removed 5.7–12.4% of total Cd content present in the nutrient solution. It was supposed that pseudomonads (soil rhizoplane bacteria) and the plant growth hormone ethylene can enhance the specific surface of roots and hence roots' metal adsorption capacity. As a trend, pretreatment of Indian mustard with Pseudomonas fluorescens bacteria enhanced slightly the Cd (from 1793 to 2346 µg g^?1) or Ni (from 1088 to 1192 µg g^?1) concentration of roots. Cadmium concentration in roots was also enhanced from 2694 to 3273 µg g^?1 when the roots of Indian mustard were pretreated with Cd‐tolerant rather than Cd‐sensitive Pseudomonas cepacia. In spite of the occurrence of new root hairs, the pretreatment of roots with ethylene proved to be ineffective in enhancement of the Cd rhizofiltration capacity of Indian mustard.     

Effects of Arsenic‐Contaminated Irrigation Water on Growth,Yield, and Nutrient Concentration in Rice

Abstract

A study was undertaken to determine the effects of different concentrations of arsenic (As) in irrigation water on Boro (dry‐season) rice (Oryza sativa) and their residual effects on the following Aman (wet‐season) rice. There were six treatments, with 0, 0.1, 0.25, 0.5, 1, and 2 mg As L^?1 applied as disodium hydrogen arsenate. All the growth and yield parameters of Boro rice responded positively at lower concentrations of up to 0.25 mg As L^?1 in irrigation water but decreased sharply at concentrations more than 0.5 mg As L^?1. Arsenic concentrations in grain and straw of Boro rice increased significantly with increasing concentration of As in irrigation water. The grain As concentration was in the range of 0.25 to 0.97 µg g^?1 and its concentration in rice straw varied from 2.4 to 9.6 µg g^?1 over the treatments. Residual As from previous Boro rice showed a very similar pattern in the following Aman rice, although As concentration in Aman rice grain and straw over the treatments was almost half of the As levels in Boro rice grain. Arsenic concentrations in both grain and straw of Boro and Aman rice were found to correlate with iron and be antagonistic with phosphorus.     

Occurrence and Geochemistry of Arsenic in Groundwater of Punjab,Northwest India

Abstract

Arsenic (As) is a deadly poison at high concentrations. It is mysterious in the sense that people are exposed to it most of the time through drinking groundwater, fortunately at much lower concentrations than the deadly levels, and usually without knowing it. Arsenic content in alluvial aquifers of Punjab varied from 3.5 to 688 µg L^?1. Arsenic status of groundwater is classified into low (<10 µg L^?1), moderate (≥10 to <25 µg L^?1), high (≥25 to <50 µg L^?1), and very high (>50 µg L^?1). In zone I, the concentration of As in groundwater varied from 3.5 to 42 µg L^?1 with a mean value of 23.4 µg L^?1. On the basis of these limits, only 8% of samples were low, whereas 51 and 41% of the total samples collected from this region fall in the moderate and high As categories. The concentration of As in groundwater of zone II varied from 9.8 to 42.5 µg L^?1 with a mean value of 24.1 µg L^?1. Arsenic concentration in the alluvial aquifers of the central plain of zone II is 2 and 52% in the low and moderate limits. In this region, 46% of groundwater sites contain high As concentrations. Arsenic concentrations in the aridic southwestern parts are significantly different from other two provinces. The As concentration ranged from 11.4 to 688 µg L^?1 with average value of 76.8 µg L^?1. Eleven percent of the aquifers of the southwestern region of zone III are in the moderate category, 54% in the high, and 35% in the very high. According to safe As limits (<10 µg L^?1), only 3 and 1% of the groundwater samples collected from zones I and II were fit for dinking purposes with respect to As content. In the aridic southwest, zone III, all water samples contained As concentrations greater than the safe limits and thus are not suitable for drinking purposes. The presence of elevated As concentrations in groundwater are generally due to the results of natural occurrences of As in the aquifer materials. The concentration of other competitive oxyanions in waters such as phosphate, sulfate, and borate also depressed the adsorption of As on the sorption sites of aquifer materials and thereby eventually elevate the As concentration in groundwaters. In groundwater of alluvial aquifers of Punjab, released from sulfide oxidation and oxyhydroxide of iron, elevated (>10 µg L^?1) concentrations of As were widespread because of high pH (>8.0) and higher concentrations of phosphate, borate, sulfate, and hydroxyl anions. It is conclusively evident that geochemical conditions, such as pH, oxidation–reduction, associated or competing ions, and evaporative environments have significant effects on As concentration in groundwater. These conditions influence how much As is dissolved or precipitated into the water and how much is bound to the aquifer materials or the solid particles in water.