Ameliorating effects of biochar on photosynthetic efficiency and antioxidant defence of Phragmites karka under drought stress.

Biochar (BC) has been reported to improve growth and drought resistance in many plants. However, adequate information on the drought resistance mechanism mediated of BC on Phragmites karka, a bioenergy plant, is not available. The impact of BC addition (0%, 0.75% and 2.5%) on plant growth and physiology of P. karka under drought was assessed. Soil water-holding capacity and soil water content were significantly improved with 0.75% BC as compared with the un-amended controls. This resulted in improved plant performance under drought conditions. An increase of parameters, such as plant fresh and dry biomass, root to shoot ratio and root mass fraction, was paralleled by an increase of chlorophyll content, net photosynthesis rate and water use efficiency of plants. Plants treated with 0.75% BC experienced less oxidative stress due to higher photosystem II efficiency and stimulated activity of antioxidant defense systems. Our results demonstrate that soil amendment with 0.75% BC allow the potential energy plant P. karka to grow in an arid habitat.

Seasonal variation in selenium status of different classes of grazing goats in a semi-arid region of Pakistan.

The selenium status of three different classes of goats ((i) female lactating, (ii) female non-lactating, and (iii) male goats) grazing semi-arid pasture in the southern part of the Punjab province, Pakistan and that of selenium concentration of soil and dietary sources, ingested by those animals were investigated during two different seasons of the year (winter and summer). Soil, forage, feed, water from the pasture and blood plasma, urine, faeces, and (if applicable) milk from these goats were collected fortnightly. The samples were analyzed for selenium concentrations. Soil selenium showed both seasonal and sampling periods effect on its concentration while forage selenium was affected only by the seasonal changes. No significant effect of seasons or fortnights on feed selenium level was observed. In fecal samples selenium concentration in lactating and non-lactating and plasma of male goats were affected by sampling periods. While fecal selenium in male goats showed significant effect on its concentration both seasonal and within fortnights. Severe deficient level of soil selenium during both seasons and marginal deficient level of forage selenium during summer were observed. Selenium concentrations in feed slightly exceeded the requirements of ruminants in feed during both seasons of the year. Plasma selenium concentrations in all goat classes were higher in winter than that in summer showing no seasonal or fortnight variation and its concentration was slightly lower in lactating goats as compared to other classes. On the bases of these results, it is concluded that overall selenium status of the goats based on plasma selenium concentration may be considered adequate mainly due to the mineral supplement provided all over the year, since soil and forage selenium concentrations were low to deficient.

Trichinella spiralis: X-ray analysis of the nurse cell-muscle larva complex after exponential growth of the larva.

The energy-dispersive X-ray analysis (EDXA) method was employed to determine how the exponential growth of the Trichinella spiralis larva affect the concentration of some metabolically active elements such as phosphorus, sulfur, sodium, chlorine, potassium, and calcium in host myocytes as well as inside the nurse cell-muscle larva complex. Two observations are noteworthy. First, the capsule of the complex reveals the highest Na+ and Cl-concentrations. We would suggest that these high Na+ and Cl-concentrations could be a part of the capsule-localized transport mechanisms covering the metabolic demands of the larva. Second, a substantial increase in the P concentration in the cells inside the complex, i.e., the nurse cell, somatic muscle of the larva, and larval stichosome was found. We postulate that energy metabolism in the nurse cell is entirely dependent on the metabolic requirements of the larva and that they remain together as one functional unit.

Compartmental nitrate concentrations in barley root cells measured with nitrate-selective microelectrodes and by single-cell sap sampling.

Nitrate-selective microelectrodes were used to measure intracellular nitrate concentrations (as activities) in epidermal and cortical cells of roots of 5-d-old barley (Hordeum vulgare L.) seedlings grown in nutrient solution containing 10 mol · m(-3) nitrate. Measurements in each cell type grouped into two populations with mean (±SE) values of 5.4 ± 0.5 mol · m(-3) (n=19) and 41.8 ± 2.6 mol · m(-3) (n = 35) in epidermal cells, and 3.2 ± 1.2 mol · m(-3) (n = 4) and 72.8 ± 8.4 mol · m(-3) (n = 13) in cortical cells. These could represent the cytoplasmic and vacuolar nitrate concentrations, respectively, in each cell type. To test this hypothesis, a single-cell sampling procedure was used to withdraw a vacuolar sap sample from individual epidermal and cortical cells. Measurement of the nitrate concentration in these samples by a fluorometric nitrate-reductase assay confirmed a mean vacuolar nitrate concentration of 52.6 ± 5.3 mol · m(-3) (n = 10) in epidermal cells and 101.2 ± 4.8 mol · m(-3) (n = 44) in cortical cells. The nitrate-reductase assay gave only a single population of measurements in each cell type, supporting the hypothesis that the higher of the two populations of electrode measurements in each cell type are vacuolar in origin. Differences in the absolute values obtained by these methods are probably related to the fact that the nitrate electrodes were calibrated against nitrate activity but the enzymic assay against concentration. Furthermore, a 28-h time course for the accumulation of nitrate measured with electrodes in epidermal cells showed the apparent cytoplasmic measurements remained constant at 5.0 ± 0.7 mol · m(-3), while the vacuole accumulated nitrate to 30-50 mol · m(-3). The implications of the data for mechanisms of nitrate transport at the plasma membrane and tonoplast are discussed.