ROLE OF PLANT GROWTH REGULATORS IN CALLUS INITIATION AND PLANTLETS REPRODUCING OF TWO ALFALFA CULTIVARS

An experiment was conducted at the central lab of Graduate studies - College of Agriculture, University of Baghdad during 2015-2016. The objective was to study the effect of growth regulator on inducing callus from embryos of two alfalfa cultivars (PAC-78001 and local) variety by tissue culture technique using factorial experiments according to CRD. Seeds sterilized by NaOCl at 4.5% for 15 minutes, then, cultured on MS media free of growth regulators to embryo induced. The embryos were cultured on MS media at different concentrations of 2,4-D (0, 1, 2, 3 and 4) mg Li-1. Induced callus from embryos was cultured on MS media supplementing with Kin. at 0, 0.25, 0.50, 0.75 and 1 mg Li-1 to determine the best concentration. The results showed that best concentration of 2,4-D and Kin were 2 and 0.5 mg L-1 respectively which gave highest callus fresh weight and callus dry weight (204.65 and 21.50) mg Li-1, respectively. BA at 2 mg Li-1 gave the highest plantlets reproducing from callus amounted 5.5 vegetative growth tube-1.

Evaluation of the Sequential Spot Sampler (S3) for time-resolved measurement of PM_2.5 sulfate and nitrate through lab and field measurements

The Sequential Spot Sampler (S3), a newly developed instrument to collect aerosols for time-resolved chemical composition measurements, was evaluated in the laboratory and field for the measurement of particulate sulfate and nitrate. The S3 uses a multi-temperature condensation growth tube to grow individual aerosols to droplets which are then deposited as a ∼ 1 mm diameter dry spot at the end of the growth tube in a 100 µL well of a multi-well plate. The well plate advances automatically to provide a sequence of time-resolved samples. The collected aerosols are subsequently analyzed in the laboratory. The sample is concentrated during the collection process, and the laboratory extraction and analysis steps can be automated. The well plate, as received from the field, is placed onto a needle-based autosampler that adds liquid for sample extraction and injects sample extract from each well onto an ion chromatograph for analysis. Laboratory evaluation for sulfate and nitrate ions showed that poly ether ether ketone (PEEK) used as well plate material does not contribute any artifacts; a 60 min extraction procedure leads to the recovery of sulfate and nitrate from the dry spots at above 95 % extraction efficiency; and samples stored frozen and analyzed up to 23 months later show less than a 10 % change in sulfate and nitrate concentrations. The limit of detection was 0.5 µg m−3 for sulfate and 0.2 µg m−3 for nitrate for a 1 h sampling period. In a month-long field study conducted in southern California, two S3s were deployed alongside a URG denuder–filter-pack and a Particle-Into-Liquid Sampler combined with an Ion Chromatograph (PILS-IC). Collocated S3 sampler concentrations compared by linear regression show good agreement, with r2 = 0.99 and slope = 0.99 (±0.004) µg m−3 for sulfate and r2 = 0.99 and slope = 1.0 (±0.006) µg m−3 for nitrate. When compared to the URG denuder–filter-pack and the PILS-IC, the S3 sulfate and nitrate concentrations yielded correlations above 0.84 for the square of the correlation coefficient and regression slopes close to 1.

Evaluation of a Sequential Spot Sampler (S3) for time-resolved measurement of PM_2.5 sulfate and nitrate through lab and field measurements

The Sequential Spot Sampler (S3), a newly developed instrument to collect aerosols for time resolved chemical composition measurements, was evaluated in the laboratory and field for the measurement of particulate sulfate and nitrate. The S3 uses a multi-temperature condensation growth tube to grow individual aerosols to droplets which are then deposited as a ~ 1 mm diameter dry spot at the end of the growth tube on a 100 μL well of a multi-well plate. The well plate advances automatically to provide a sequence of time-resolved samples. The collected aerosols are subsequently analyzed in the laboratory. The sample is concentrated during the collection process and the laboratory extraction and analysis steps can be automated. The well plate, as received from the field, is placed onto a needle-based autosampler that adds liquid for sample extraction and injects sample extract from each well onto an ion chromatograph for analysis. Laboratory evaluation for sulfate and nitrate ions showed that PEEK used as well plate material does not contribute any artifacts; a 60 min extraction procedure leads to the recovery of sulfate and nitrate from the dry spots at above 95 % extraction efficiency; and samples stored frozen and analyzed up to 23 months later show less than a 10 % change in sulfate and nitrate concentrations. In a month long field study conducted in Southern California, two S3s were deployed alongside a URG denuder/filter-pack and a Particle-Into-Liquid Sampler combined with an Ion Chromatograph (PILS-IC). Collocated S3 sampler concentrations compared by linear regression show good agreement with r2 = 0.99 and slope = 0.99 (±0.004) μg m−3 for sulfate and r2 = 0.99 and slope =1.0 (±0.006) μg m−3 for nitrate. When compared to the URG denuder/filter-pack and the PILS-IC, the S3 sulfate and nitrate concentrations yielded correlations above 0.84 for the square of the correlation coefficient and regression slopes close to one.