NITRATE UPTAKE KINETICS AND METABOLIC PARAMETERS IN TWO RICE VARIETIES GROWN IN HIGH AND LOW NITRATE

A study was conducted on the effect of nitrate (NO₃) levels on nitrate uptake kinetics and nitrogen (N) metabolism in two rice varieties, Piaui (landrace) and IAC-47 (improved). At 27 days after germination (DAG) N supply was suspended for 72 h, and then restored as 0.2 or 2 mM nitrate. The nitrate uptake kinetics was determined by the depletion method. Plants were harvested at 0, 6, and 24 h. Plants of the Piaui variety under 0.2 mM nitrate showed higher V_max and lower K_M, indicating higher efficiency of nitrate uptake at low supply. In the sheaths of both varieties, there was a greater accumulation of nitrate and lower activities of nitrate reductase and glutamine synthetase. The V-H⁺-ATPase activity increased between 0 and 6 h accompanying the nitrate influx, suggesting that the activity of this proton pump is necessary for the antiport activity (H⁺/2NO^? ₃) involved in the accumulation of nitrate into vacuoles.     

Are government veterinary paraprofessionals serving the poor? The perceptions of smallholder livestock farmers in Western Kenya

The liberalization of clinical veterinary services in Kenya introduced new service providers into the animal health service sector. This study examines the perceptions of livestock farmers regarding these service providers and analyses the factors that influence their choice of alternative service providers in Kakamega County. The empirical analysis shows that private animal health assistants were perceived to provide better services than alternative providers because they are more accessible and offer services on credit. Results from a multinomial logit model reveal that more educated, wealthier, and older farmers are more likely to use government services. The study concludes that it is imperative to better target the poor and to integrate private service providers into government animal health programs.

     

Effects of Fusicoccin and Vanadate on Proton Extrusion and Potassium Uptake by Rice

The effects of fusicoccin or vanadate on proton (H⁺) extrusion and potassium (K) uptake of four varieties of rice (oryza satiya L.) were studied. Two of them were improved varieties (IAC-47 and Agulha), with 70% genetic similarity. The two others were landraces (Bico Ganga and Piaui). Vanadate totally blocked H⁺-pumping activity while fusicoccin increased it. Potassium uptake was suppressed under vanadate but increased sharply under the fusicoccin treatment. The Piaui was the most affected by fusicoccin, while Agulha was the least affected. Under fusicoccin, Bico Ganga had a 48% increase in K uptake at the end of the experimental period in relation to the controls, while IAC-47 showed only a 17% increase. Taken together, for all varieties and treatments, there was a negative correlation between the final pH and the total K taken up by plants. This study suggests that some rice varieties need additional stimulation from external sources to express their full H⁺-pumping and K-uptake capabilities.     

The effects of temperature and pressure on the characteristics of the extracts from high-pressure CO(2) extraction of Majorana hortensis Moench

The aim of this work is to assess the influence of temperature and pressure (solvent density) on the characteristics of the essential oil obtained from high-pressure carbon dioxide extraction of marjoram (commercial marjoram samples available in the free market and Majorana hortensis Moench, cultivated in South Brazil under rigorous agronomic conditions). The extracts were analyzed in terms of the liquid yield (extract/raw material, wt/wt) and distribution of volatile chemical components. The experiments were performed in a laboratory-scale unit using the dynamic method in the temperature range of 293.15-313.15 K, from 100 to 200 bar in pressure. Chemical analyses were carried out in a GC/MSD. Results show that an increase in temperature leads to a rise in the extract liquid yield despite large changes in solvent density. Chromatographic analyses permitted the identification of cis-sabinene hydrate, terpineol-4, alpha-terpineol, and cis-sabinene hydrate acetate as the main volatile compounds present in both commercial and cultivated samples.