Mrittunjai Srivastava

Effects of selenium on arsenic uptake in arsenic hyperaccumulator Pteris vittata L.

Selenium (Se) is a non-metallic element, which has the capability to increase the antioxidative capacity and stress tolerance of plants to heavy metals. Plants vary considerably in their physiological response to Se. The reported research investigated the effects of Se on arsenic (As) uptake by As hyperaccumulator Pteris vittata L. and determined possible mechanisms of interaction. Pteris vittata plants were exposed hydroponically to 0, 150 or 300 microM of Na(2)HAsO(4) in the presence of 0, 5 or 10 microM of Na(2)SeO(4) for 5 or 10d. Application of 5 microM Se enhanced As concentration by P. vittata fronds by 7-45%. At 5 microM, Se acted as an antioxidant, inhibiting lipid peroxidation (reduced by 26-42% in the fronds) via increased levels of thiols and glutathione (increased by 24% in the fronds). The results suggest that Se is either an antioxidant or it activates plant protective mechanisms, thereby alleviating oxidative stress and improving arsenic uptake in P. vittata.

Effect of fertilizer amendments on phytoremediation of Cd-contaminated soil by a newly discovered hyperaccumulator Solanum nigrum L.

Phytoremediation is a cost-effective, simple and sustainable beneficiary technique to purify the polluted environment. Solanum nigrum L., a newly found cadmium (Cd) hyperaccumulator, has shown the potential to remediate Cd-contaminated soils. Present study investigated the effects of fertilizer amendments on the Cd uptake by S. nigrum. Chicken manure and urea are usual agricultural fertilizers and more environmental friendly. The results showed that Cd concentrations in shoots of S. nigrum were significantly decreased (p<0.05) by 28.2-34.6%, as compared to that of without the addition of chicken manure, but not the case for urea treatment. However, Cd extraction capacities (microg pot(-1)) in shoot biomass of S. nigrum were significantly increased (p<0.05) due to increased shoot biomass. In addition, available Cd concentration in soil significantly decreased due to addition of chicken manure. Thus, urea might be a better fertilizer for strengthening phytoextraction rate of S. nigrum to Cd, and chicken manure may be a better fertilizer for phytostabilization.

UPTAKE AND DISTRIBUTION OF SELENIUM IN DIFFERENT FERN SPECIES

Abstract There has been an interest in using hyperaccumulating plants for the removal of heavy metals and metalloids. High selenium (Se) concentrations in the environment are detrimental to animals, humans, and sustainable agriculture, yet selenium is also an essential nutrient for humans. This experiment was conducted to screen fern plants for their potential to accumulate selenium. Eleven fern species, Pteris vittata, P. quadriaurita, P. dentata, P. ensiformis, P. cretica, Dryopteris erythrosora, Didymochlaena truncatula, Adiantum hispidulum, Actiniopteris radiata, Davallia griffithiana, and Cyrtomium fulcatum, were grown under hydroponic conditions for one week at 20 mg L− 1 selenate or selenite. Root Se concentrations reached 245–731 and 516–1082 mg kg− 1 when treated with selenate and selenite, respectively. The corresponding numbers in the fronds were 153–745 and 74-1,028 mg kg− 1 with no visible toxicity symptoms. Only three fern species were able to accumulate more Se in the fronds than the roots, which were D. griffithiana when treated with selenate, P. vittata when treated with selenite, and A. radiata regardless of the forms of Se. A. radiata was the best species overall for Se accumulation. More research is needed to further determine the potential of the fern species identified in this study for phytoremediation of the Se contaminated soils and water.

Comparison of arsenic accumulation in 18 fern species and four Pteris vittata accessions

This study evaluated the ability and mechanisms of 19 Pteris and non-Pteris species to accumulate arsenic (As) in a hydroponic system spiked with 300 microM As. The study included four Pteris vittata accessions (China, India, Poland, and the United Kingdom), P. biaurita and 17 non-Pteris species. Among the accessions, P. vittata from China and UK were the most and the least efficient in terms of As accumulation. The non-Pteris species Chielanthes sinuta, Adiantum raddianum, Polystichum acrostichoides, Actiniopteris radiata, Pellaea rotundifolia, and Nephrolepis cordifolia concentrated As as effectively as the least efficient P. vittata ascension. As (III) in the fronds of P. vittata accessions ranged from 59% to 89% and for non-Pteris species it ranged from 47% to 65%. Maximum As accumulation coincided with highest percentage of As (III) in the fronds. The phosphorus (P) uptake of P. vittata accessions was 12-15 and 6-12 times greater than the As-uptake in the roots and fronds, respectively. In contrast, the P-uptake of non-Pteris species ranged from 9 to 151 and from 4 to 162 times the As-uptake, in the roots and fronds, respectively. Arsenic accumulation occurs at the expense of root and frond P-uptake. Root P-reduction is lower than frond and the P:As in the plant acquisition part (roots) is 1-3 times greater than that in accumulation part (fronds). A. radiata, C. sinuta, and P. acrostichoides were identified as potential As accumulators.

Evaluation of Imidacloprid and Cyantraniliprole for Suitability in Conservation Biological Control Program for Orius insidiosus (Hemiptera: Anthocoridae) in Field Pepper

A biologically based integrated pest managefor pepper by Funderburk et al. (2000) and Reitz et ment program is fundamental in preventing al. (2003). Experimental design was a randomized the development of insecticide resistance, recomplete block, with 4 replications. Plot size was 1 surgence of populations of western flower thrips, raised, plastic mulched bed 9 m long on which there Frankliniella occidentalis (Pergande) (Thysanopwere 2 linear rows of pepper with a 13.8-cm plant tera: Thripidae), and replacement with nontarget spacing between and within rows for a total of 48 pest damage (Demirozer et al. 2012). The conservaplants per plot. Beds were irrigated with a single tion biological control component of the integrated trickle tube with emitters spaced every 30 cm at a pest management program is the most effective rate of 20,000 Ivha/day. Dates and rates of insecti way to manage thrips in pepper (Capsicum spp.; cide applications and of insect sampling are includ Solanales: Solanaceae) (Reitz et al. 2003). Species ed in Table 1. Foliar insecticides were applied with a of Anthocoridae are the most important worldwide C02-powered backpack sprayer equipped with 4 D7 predators of thrips. Within this family are minute nozzles with the amount of spray 430 L/ha. Drench pirate bugs with 2 species in Florida, Orius insidiotreatments were applied in a water solution of 200 sus (Say) and O. pumilio (Champion) (Hemiptera: mL/plant. Trickle tube treatments were applied in Anthocoridae). The minute pirate bugs are a valua water solution of 5.7 L/plot with a C02-powered able tool for controlling thrips as they prey preferinjector pressurized to 103 kPa, followed by 8 L of entially on the adults of the western flower thrips clean water rinse. Inline connectors with shut-off over the adults of the non-damaging native thrips valves were used to isolate the plots. Ten flowers species, F. tritici (Fitch) and F. bispinosa (Morgan) per plot (whenever possible) were collected on each (Baez et al. 2004). The damaging thrips larvae also of 6 sample dates and preserved in 70% alcohol with are preferred prey (Baez et al. 2004). About 1 minthe number of thrips and O. insidiosus determined ute pirate bug for every 180 thrips is sufficient for using 7 to 100 X magnification. The data for each suppression of the populations of thrips, and at a sample was converted to number per flower, pooled ratio of about 1 predator to 40 thrips, thrips populaover date, and transformed to log (x + 0.5) for anal tions are controlled (Funderburk et al. 2000). Natuysis of variance. When the overall treatment effect ral populations of minute pirate bug adults rapidly was significant at the P = 0.05 level, orthogonal invade pepper fields in sufficient numbers to control comparisons were used to separate treatment dif western flower thrips adults and larvae, but they ferences. Untransformed means per 10 flowers are must be conserved with judicious insecticide use reported in Table 1. (Funderburk et al. 2000, Demirozer et al. 2012). The adults of F. occidentalis and F. tritici ac An integrated pest management program for counted for 6 and 19% of the total thrips in the rm peppers that encompasses the simultaneous mantreated controls and there were no significant treat agement of multiple pests is being developed and ment differences (data not shown). The numbers of implemented (Demirozer et al. 2012). Ta further thrips were well below the economic thresholds es enhance the effectiveness of the conservation biotablished by Demirozer et al. (2012), with the ratio logical control component of this program, updated of predators in relation to prey sufficient in the cm information on insecticides labeled for fruiting vegtreated plots to result in thrips suppression. There etables against thrips or other pests that have little were treatment differences in the number of F. impact on populations of minute pirate bugs was bispinosa females, thrips larvae, and O. insidiosus reported (Funderburk et al. 2011). In the present nymphs (Table 1). When compared to the untreat report, imidacloprid 4.6SC (Bayer Crop Protection, ed control, 2 applications of cyantraniliprole 20SC Research Triangle Park, North Carolina) and cyanin the trickle tube did not reduce the numbers of traniliprole 10SE and 20SC (DuPont Crop Protecthrips or O. insidiosus in the flowers. However, the tion, Newark, Delaware) were evaluated against 2 applications of cyantraniliprole 20SC combined populations of thrips and minute pirate bugs, with a transplant treatment of imidacloprid 4.6SC Spinetoram SC (Dow AgroSciences, Indianapolis, resulted in 94, 82, and 88% reductions in numbers Indiana) was included as a standard foliar treatof F. bispinosa adults, thrips larvae, and O. insid ment. iosus nymphs, respectively. Unless there are unex Experimental procedures to evaluate the treatpected synergistic effects, this result showed that ment effects on adult and immature O. insidiosus the residual effect of a transplant application of and flower thrips were similar to those established imidacloprid lasted through pepper flowering and

Kalimeris integrifolia Turcz. ex DC.: An accumulator of Cd

Phytoremediation is a traditional technique that uses vegetation to remediate contaminants from water, soil and sediments. This is a solar-driven, aesthetically pleasing, and cost effective technology. In a former published article, Kalimeris integrifolia Turcz. ex DC. indicated some basic properties of hyperaccumulators for cadmium (Cd). In this study, concentration gradient experiment and sample-analyzing experiments were used to assess whether this plant is a Cd-hyperaccumulator. The results showed the Cd enrichment factor (concentration in plant/soil) and Cd translocation factor (concentration in shoot/root) of K. integrifolia was basically >1 in concentration gradient experiment. Shoot biomass was not reduced significantly (p<0.05) compared to the control. However, the Cd concentration in K. integrifolia shoots was not higher than 100 mg kg(-1), the threshold concentration for a Cd-hyperaccumulator. Thus, K. integrifolia should only be considered as a Cd-accumulator. In the sample-analyzing experiments conducted in a Pb-Zn mine area and a wastewater irrigation region, K. integrifolia also showed Cd-accumulator properties. Based on these results, K. integrifolia could be identified as a Cd-accumulator.

Bidens tripartite L.: A Cd-accumulator confirmed by pot culture and site sampling experiment

Characteristics of accumulation and tolerance of cadmium (Cd) in Bidens tripartite L. were investigated to identify Cd-accumulating properties. In this study, pot culture experiment and site sampling experiments were conducted to assess whether this plant is a heavy metal hyperaccumulator or accumulator. The results indicated that the Cd enrichment factor (concentration in plant/soil) and Cd translocation factor (concentration in shoot/root) of B. tripartite was principally >1 in pot culture and concentration gradient experiments. Shoot biomass was not reduced significantly (p<0.05) compared to the controls. However, the Cd concentration in B. tripartite shoots was not higher than 100 mg kg(-1), the threshold concentration for a Cd-hyperaccumulator. In the site sampling experiment, B. tripartite also showed Cd-accumulator properties. Based on these results, B. tripartite could be identified as a Cd-accumulator. Thus, B. tripartite should only be considered as a Cd-accumulator.

Impacts on Natural Enemies and Competitor Thrips of Insecticides against the Western Flower Thrips (Thysanoptera: Thripidae) in Fruiting Vegetables

Abstract Newer, selective insecticides with few negative impacts on natural enemies and competitor species are needed for effective, sustainable management of the western flower thrips, Frankliniella occidentalis (Pergande). The purpose of this study was to evaluate the impacts on natural enemies and competitor thrips species of insecticides used for control of western flower thrips in fruiting vegetables. Trials with tomato (Solanum lycopersicum L.) and with pepper (Capsicum annuum L.) were conducted to evaluate insecticide treatment effects on western flower thrips and natural enemies at the North Florida in 2008, 2009, 2010 and 2011. A number of insecticides from different classes showed moderate to high efficacy against western flower thrips. The broad-spectrum insecticides acetamiprid, methomyl, and tolfenpyrad demonstrated activity against the pest, while also reducing populations of the key predator of thrips in pepper, Orius insidiosus (Say) (Hemiptera: Anthocoridae). Insecticides that showed little impact on populations of O. insidiosus were cyantraniliprole, flonicamid, spirotetramat, and terpenes. Although only moderately active against the western flower thrips, they would be valuable additions to existing management programs for pepper. Insecticides with activity against western flower thrips also showed activity against Frankliniella tritici (Fitch). This non-damaging congener species is a beneficial because it out-competes the western flower thrips, especially in tomato where O. insidiosus is not a major factor in western flower thrips management. Numerous insecticides were identified with activity against the western flower thrips that are suitable for use in integrated pest management programs of fruiting vegetables.

Seed germination of a newly discovered hyperaccumulator Solanum nigrum L. affected by illumination and seed-soaking reagent.

Solanum nigrum is a newly found Cd-hyperaccumulator which showed very high remediation efficiency in polluted soil. Seed germination experiments with different illumination and seed-soaking reagents were conducted in constant temperature box and greenhouse with soil as burgeon base. The results showed that the germination rate with alternating light/dark photoperiod was about twice of that without lighting (p < 0.05), suggesting that illumination is one of the important conditions for seed germination of S. nigrum. All treatments with seed-soaking reagents significantly increased the seed germination rate of S. nigrum (p < 0.05). Treatment with H2O2 (0.1%) had the shortest germination time. The germination rate of seeds that were not washed in water following soaking was 2-3 times higher than that of seeds that were washed after soaking.

Biotic resistance limits the invasiveness of the western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), in Florida

The spread of the western flower thrips, Frankliniella occidentalis (Pergande), has resulted in the world‐wide destabilization of established integrated pest management programs for many crops. It is hypothesized that frequent exposure to insecticides in intensive agriculture selected for resistant populations, which allowed invasive populations in the eastern USA to overcome biotic resistance from the native community of species. Research conducted in Florida to understand the role of biotic factors in limiting the abundance of the western flower thrips is reviewed. Orius spp. (Hemiptera: Anthocoridae) are effective predators that suppress populations of thrips on crop and non‐crop hosts in southern and northern Florida. Orius are more effective predators of the western flower thrips than the native flower thrips, F. tritici (Fitch) and F. bispinosa (Morgan). The native species are competitors of the western flower thrips. Excessive fertilization and the use of broad‐spectrum insecticides in crop fields further enhances populations of the western flower thrips. Interactions with native species clearly limit the abundance of western flower thrips in Florida, but populations are abundant in fertilized crop fields where application of insecticides excludes predators and competitor species.