33 research outputs found
Determination of the uptake and translocation of nitrogen applied at different growth stages of a melon crop (Cucumis melo L.) using 15N isotope.
In order to establish a rational nitrogen (N) fertilisation and reduce groundwater contamination, a clearer understanding of the N distribution through the growing season and its dynamics inside the plant is crucial. In two successive years, a melon crop (Cucumis melo L. cv. Sancho) was grown under field conditions to determine the uptake of N fertiliser, applied by means of fertigation at different stages of plant growth, and to follow the translocation of N in the plant using 15N-labelled N. In 2006, two experiments were carried out. In the first experiment, labelled 15N fertiliser was supplied at the female-bloom stage and in the second, at the end of fruit ripening. Labelled 15N fertiliser was made from 15NH415NO3 (10 at.% 15N) and 9.6 kg N haâ1 were applied in each experiment over 6 days (1.6 kg N haâ1 dâ1). In 2007, the 15N treatment consisted of applying 20.4 kg N haâ1 as 15NH415NO3 (10 at.% 15N) in the middle of fruit growth, over 6 days (3.4 kg N haâ1 dâ1). In addition, 93 and 95 kg N haâ1 were supplied daily by fertigation as ammonium nitrate in 2006 and 2007, respectively. The results obtained in 2006 suggest that the uptake of N derived from labelled fertiliser by the above-ground parts of the plants was not affected by the time of fertiliser application. At the female-flowering and fruit-ripening stages, the N content derived from 15N-labelled fertiliser was close to 0.435 g mâ2 (about 45% of the N applied), while in the middle of fruit growth it was 1.45 g mâ2 (71% of the N applied). The N application time affected the amount of N derived from labelled fertiliser that was translocated to the fruits. When the N was supplied later, the N translocation was lower, ranging between 54% at female flowering and 32% at the end of fruit ripening. Approximately 85% of the N translocated came from the leaf when the N was applied at female flowering or in the middle of fruit growth. This value decreased to 72% when the 15N application was at the end of fruit ripening. The ammonium nitrate became available to the plant between 2 and 2.5 weeks after its application. Although the leaf N uptake varied during the crop cycle, the N absorption rate in the whole plant was linear, suggesting that the melon crop could be fertilised with constant daily N amounts until 2â3 weeks before the last harvest
Crescimento e mortalidade de Oligosarcus hepsetus (Cuvier, 1829) (Characiformes, Characidae) no Parque Estadual da Serra do Mar, NĂșcleo Santa VirgĂnia, SĂŁo Paulo, Brasil
Determinação dos teores de nitrogĂȘnio na seiva do tomateiro por meio de medidor portĂĄtil
Aquecimento global: efeitos no crescimento, no desenvolvimento e na produtividade de batata
Signaling to P-glycoprotein-A new therapeutic target to treat drug-resistant epilepsy?
Item does not contain fulltextEpilepsy affects more than 60 million people worldwide. While most patients can be treated with antiepileptic drugs, up to 40% of patients respond poorly to pharmacotherapy. This drug resistance is not well understood and presents a major clinical problem. In this short review we provide background information on one potential cause of antiepileptic drug resistance, namely, upregulation of the drug efflux transporter P-glycoprotein at the blood-brain barrier. We summarize recent findings that connect antiepileptic drug resistance with P-glycoprotein upregulation and show a mechanistic link between seizures and upregulation of this transporter. We provide an overview of results demonstrating that glutamate released during seizures signals through N-methyl-Daspartate (NMDA) receptor and cyclooxygenase-2 (COX-2) to increase P-glycoprotein. In this context we discuss the NMDA receptor and COX-2 as potential therapeutic targets and provide information on current clinical trials on drugresistant epilepsy involving blood-brain barrier efflux transporters. Finally, we provide a perspective on future research that could help improve the treatment of drug-resistant epilepsy