The effect of zirconium oxide nanoparticles on dehydrogenase and hydrolytic activity of activated sludge microorganisms

The pervasive use of engineered nanoparticles (NPs) in a wide range of fields raises concerns about their potential environmental impacts. The impact of NPs on the activity of enzymes in sewage sludge was examined using model engineered zirconium oxide nanoparticles (nano-ZrO2). Dehydrogenase activity was evaluated with the TTC test and hydrolytic activity with FDA test. In this study an inhibitory or a stimulating effect of NPs on the activity of the enzymes was observed. The levels of inhibition/stimulation of the nano-ZrO2 varied in relation to duration of contact NPs with activated sludge and particle size (nano, bulk).

Assessment of Pollen Viability, Germination, and Tube Growth in Eight Tunisian Caprifig (Ficus carica L.) Cultivars

The evaluation of pollen viability and its germination capacity are two essential criteria for pollinator’s characterization. This study was carried out to evaluate pollen quality of eight caprifigs grown in the center-east and north-west of Tunisia. Two colorimetric tests 2,3,5-triphenyl tetrazolium chloride (TTC) and acetocarmine were used to estimate pollen viability. Germination rate and pollen tube growth in a culture medium containing 5% sucrose, 5 ppm boric acid (H3BO3) and 1% agar were registered after 24, 48, and 72 hours (H) of incubation. Results showed that the highest pollen viability rate (84%) was obtained by TTC test in caprifig Assafri, followed by Jrani (80.2%), Djebba 2 (77.8%), and Djebba 1 (73.6%). That of other caprifigs did not exceed 50% for the two tests. In all caprifig types, germination rate and pollen tube growth varied according to the incubation period. The highest percentage of germination (72%) and maximum pollen tube length (960 μm) were recorded after 72 H of incubation in caprifigs Assafri and Jrani, respectively. Among the caprifigs studied, four types (Assafri, Jrani, Djebba 1, and Djebba 2) appeared to be suitable pollinators with respect to the criteria investigated.

Tetrazolium test for evaluating triticale seed viability

Freshly harvested triticale seeds are usually dormant, making the immediate evaluation of the physiological potential of seed lots difficult. We evaluated different triphenyl tetrazolium chloride (TTC) test methods for rapidly determining the viability of four seed lots of x.Triticosecale Wittmack cultivar IPR111. The test variables were: Preconditioning, (i) placing whole seeds between moistened paper towels or (ii) directly soaking the seeds in water, both procedures being conducted at 20 ºC for 18 hours; Post-conditioning seed preparation, (i) longitudinal bisection of the seed through the embryo with one half being stained and the other discarded or (ii) longitudinal bisection with both halves being stained; Staining for three and four hours, in the dark, with 0.1%, 0.5% or 1.0% (w/v) TTC according to the preconditioning method described above, (i) both halves of each seed were placed on filter paper moistened with TTC and maintained at 40 ºC or (ii) one half of each seed was immersed in 5 mL of TTC solution in a 100 mL glass beaker at 30 ºC. The best results were obtained by preconditioning seeds between moistened paper towels at 20 ºC for 18 hours and staining on filter paper with 1.0% (w/v) TTC for three hours at 40 ºC.

Germination Responses of Some Forage Species of Eastern Terai, Nepal

Freshly harvested seeds of the species (legumes: Alysicarpus vaginalis and Desmodium triflorum; grasses. Axonopus compressus and Chrysopogon aciculatus) failed to germinate even after acid scarification and incubation under different light qualities, whereas seven-nine-month old seeds exhibited germination in the order: D. triflorum (23%) > A. compresses (17%) > A. vaginalis (13%) > C. aciculatus (4%) without acid scarification or nutrient treatment. The legumes contained yellowish brown (Yb) and brick-red (Br) seeds in their pods in the ratio of 4:1. The Yb seeds had hard seed covering very slowly permeable to water. Storage of seeds under room conditions in sealed polythene pouches up to three years profoundly inhibited germination in Br seeds but had little effect on Yb seeds. The nine-month-old Br seeds had maximum germination (24 and 38%, respectively in A. vaginalis and D. triflorum) when submerged in water for 24 h before sowing, whereas germination in submerged in water for three days as a pretreatment. Germination in Yb seeds of the same age was 72 and 77%, respectively in A. vaginalis and 84% in D. triflorum when seven-eight-month old seeds were scarified with mixed (Yb and Br) seed lot was 71% in A. vaginalis and 84% in D. triforum when seven-eight-month old seeds were scarified with sulphuric acid for 10 min and incubated under red light for a week. The fresh seeds of A. compressus had 79% in viability (TTC test) which declined to 5% after storage for three years, and nine-month-old caryopses when treated with nitric acid for ten minute and incubated under red light for 18 days had maximum (45%) germination. In C. aciculatus. Seeds had only 37% viability when fresh, and they completely lost viability after storage for two years, and nine-month old caryopses had maximum (17%) germination when treated with 0.5% solution of potassium nitrate and incubated under ordinary condition for 25 days.Key words: Seed attributes; storage; viability; acid scarification; light; imbibition; potassium niratedoi: 10.3126/eco.v13i0.1629Ecoprint (An international Journal of Ecology) Vol.13, 2006 page 49-60

In vitro and in vivo screening for cold tolerance in winter × spring wheat-derived doubled haploids following the wheat × maize system

Seventy-eight doubled haploid (DH) lines, derived from 21 elite and diverse winter × spring wheat F 1 hybrids, following the wheat × maize system, were screened along with the parental genotypes under in vitro and in vivo conditions for cold tolerance. Under in vitro conditions, the 2,3,5-triphenyl tetrazolium chloride (TTC) test was used to characterize the genotypes for cold tolerance. Based on the TTC test, only one doubled haploid, DH 69, was characterized as cold-tolerant, seven DH and five winter wheat parents were moderately tolerant, while the rest were susceptible. Analysis of variance under in vivo conditions also indicated the presence of sufficient genetic variability among the genotypes (DH lines + parents) for all the yield-contributing traits under study. The correlation and path analysis studies underlined the importance of indirect selection for tillers per plant, harvest index and grains per spike in order to improve grain yield. It was also concluded that selection should not be practised for grain weight per spike as it would adversely affect the grain yield per plant. When comparing the field performance of the genotypes with the in vitro screening parameters, it was concluded that in addition to the TTC test, comprising a single parameter, other physiological and biochemical in vitro parameters should be identified, which clearly distinguish between cold-tolerant and susceptible genotypes and also correlate well with their performance under field conditions.

Evaluation of heavy metal inhibition of activated sludge by TTC and INT-electron transport system activity tests

TTC and INT-electron transport system activity tests were compared for assessing heavy metal inhibition of activated sludge. The median inhibitory concentrations (IC50s) of Cu2+, Zn2+, Cd2+, Hg2+, Ni2+, Pb2+ and Ag+ measured via TTC test were lower than those measured via INT test, which indicates that the INT-electron transport system activity test was less sensitive to heavy metal toxicity than the TTC test. Tested heavy metals brought about similar decrease in TTC-electron transport system activity and COD removal rate, but less decrease in INT-electron transport system activity than COD removal rate, which suggests that the TTC-electron transport system activity is a better parameter for reflecting heavy metal inhibition of activated sludge than INT-electron transport system activity. The ranking of tested heavy metals in order of decreasing toxicity based on TTC test was Hg2+, Cd2+, Cu2+, Ag+, Zn2+, Ni2+ and Pb2+, and the ranking based on INT test was Hg2+, Ag+, Cu2+, Cd2+, Zn2+, Ni2+ and Pb2+.