Posição da folha e estádio fenológico do ramo para análise foliar do pinhão-manso Leaf position and phenological stage of branch for leaf analysis of Jatropha plants

A análise foliar é uma ferramenta imprescindível na predição de possíveis desordens nutricionais e avaliação do estádio nutricional das plantas. Este procedimento só é efetivo se a amostragem for feita com padronização da posição da folha no ramo e do tipo de ramo. Objetivou-se com este trabalho definir a posição da folha no ramo e o tipo de ramo mais apropriado para diagnosticar o estádio nutricional de plantas de pinhão-manso. O ensaio consistiu de uma combinação fatorial (5 x 2), com cinco posições da folha no ramo (1º, 2º, 3º, 5º e 10º nós do ramo do ápice para a base) e dois tipos de ramo (vegetativo ou florífero) em delineamento inteiramente casualizado com quatro repetições. Cada amostra de folha foi colhida em 4 ramos secundários de 20 plantas na fase de florescimento. As folhas das posições 2 e 3 são as mais adequadas para análise foliar de N, P, K, S, Cu, Fe, Mn e Zn, pois apresentam valores médios mais estáveis quando comparadas com as demais posições estudadas. As folhas nas posições 5 ou 10 são mais apropriadas para avaliação de Ca e Mg. O estádio fenológico do ramo não influencia os teores de nutrientes, exceto de Cu e Fe.<br>Leaf analysis is an important tool for prediction of nutritional disorders and evaluation of nutritional status of plants. This procedure only can be effective if samples are standardized regarding leaf position and phenological stage of the branch. This study had the objective of defining the most appropriate leaf position and type of branch for nutritional diagnosis of Jatropha plants. A factorial combination of five leaf positions (1st, 2nd, 3rd, 5th, and 10th node from apex to base) and two types of branch (vegetative and flowering) was adopted in a completely randomized design with four replications. Each leaf sample was collected in 4 secondary branches of 20 plants in the flowering phase. Leaves in the position 2 and 3 are the most adequate for analyzing N, P, K, S, Cu, Fe, Mn, and Zn, because they present mean values more stable when compared to the other studied positions. Leaves in the position 5 and 10 are more adequate for analyzing Ca and Mg. The phenological stage of the branch does not influence nutrient content, except of Cu and Fe

OSR1-sensitive renal tubular phosphate reabsorption

Background: The oxidative stress-responsive kinase 1 (OSR1) participates in the WNK-(with no K) kinase dependent regulation of renal salt excretion and blood pressure. Little is known, however, about the role of OSR1 in the regulation of further renal transport systems. The present study analyzed the effect of OSR1 on NaPiIIa, the major renal tubular phosphate transporter. Methods: Immunohistochemistry and confocal microscopy were employed to determine renal localization of OSR1 and NaPiIIa. To elucidate the effect of OSR on NaPiIIa activity, cRNA encoding NaPiIIa was injected into Xenopus oocytes with or without additional injection of cRNA encoding OSR1, and phosphate transport was estimated from phosphateinduced currents determined with dual electrode voltage clamp. To elucidate the in vivo significance of OSR1 serum phosphate and hormone concentrations as well as urinary phosphate output of mice carrying one allele of WNK-resistant OSR1 (osr1(tg/+)) were compared to the respective values of wild type mice (osr1(+/+)). Results: NaPiIIa and OSR1 were both expressed in proximal renal tubule cells. Coexpression of OSR1 significantly up-regulated phosphate-induced currents in NaPiIIa-expressing Xenopus oocytes. Despite decreased serum phosphate concentration urinary phosphate excretion was significantly increased and NaPiIIa protein abundance in the brush border membrane significantly reduced in osr1(tg/+) mice as compared to osr1(+/+) mice. Serum PTH and calcitriol levels were similar in osr1(tg/+) mice and in osr1(+/+) mice, serum FGF23 concentration was, however, significantly higher in osr1(tg/+) mice than in osr1(+/+) mice. Conclusions: OSR1 is expressed in proximal renal tubules and participates in the regulation of FGF23 release and renal tubular phosphate transport