Deficiencias minerales en plantas de una savia de dos especies de frondosas mediterráneas (Quercus suber L. y Ceratonia siliqua L.)

Mineral deficiencies are common during the seedling growth in forestry nurseries, as well as during the initial establishment of the plantations. The aim of this work was to study the effects of nitrogen, phosphorus, potassium and iron deficiencies in two Mediterranean hardwood species: Quercus suber L. and Ceratonia siliqua L. The test was made in hydroponic liquid culture, using solutions lacking N, P, K or Fe and a control solution. The test lasted 139 days for Quercus suber and 190 days for Ceratonia siliqua, and was developed with 50% of shade. During this period, morphological attributes (height, dry weight of aerial part and root) and physiological attributes (relative chlorophyll content and nutrient concentration in leaves) were determined, as well as the visible symptoms caused by the respective nutrient deficiencies. Nutrient deficiencies affected morphological and physiological attributes, and in some cases visual symptoms appeared. In addition, other determinations like relative chlorophyll content (SPAD) and nutrient foliar concentration are suggested to assure a correct diagnosis.Las deficiencias minerales son comunes en el cultivo de brinzales de especies forestales en vivero, así como durante el establecimiento inicial de las plantaciones. El presente trabajo tiene por objetivo el estudio de los efectos de las deficiencias de nitrógeno, fósforo, potasio y hierro en dos especies de frondosas mediterráneas: Quercus suber L. y Ceratonia siliqua L. El ensayo se realizó en cultivo hidropónico en medio líquido, utilizando soluciones nutritivas deficientes en N, P, K y Fe y una solución control. El cultivo se mantuvo durante 139 días para Quercus suber y 190 días para Ceratonia siliqua en un umbráculo con 50% de sombra. Durante este periodo se determinaron atributos morfológicos (altura, peso seco de parte aérea y de raíz) y fisiológicos (contenido relativo de clorofila y concentración de nutrientes en hojas), así como los síntomas visibles provocados por las respectivas carencias nutritivas. Las deficiencias nutritivas afectaron a los atributos morfológicos y fisiológicos, y en algunos casos aparecieron síntomas en hojas. No obstante, los síntomas visuales no parecen ser un método de diagnóstico muy preciso para las especies estudiadas, salvo en el caso de la deficiencia de Fe. Las variaciones en el crecimiento y las concentraciones de nutrientes en hojas han mostrado una mayor sensibilidad, por lo que los estudios alométricos y de nutrición pueden representar alternativas más precisas para los estudios nutricionales de especies de frondosas mediterráneas. El contenido relativo de clorofila (SPAD) también puede ser de utilidad en el diagnóstico de algunas de las deficiencias nutritivas, si se calibran sus valores para cada especie

The opposite effect of convulsant drugs on neuronal and endothelial nitric oxide synthase – A possible explanation for the dual proconvulsive/anticonvulsive action of nitric oxide

Nitric oxide (NO) participates in processes such as endothelium-dependent vasodilation and neurotransmission/neuromodulation. The role of NO in epilepsy is controversial, attributing it to anticonvulsant but also proconvulsant properties. Clarification of this dual effect of NO might lead to the development of new antiepileptic drugs. Previous results in our laboratory indicated that this contradictory role of NO in seizures could depend on the nitric oxide synthase (NOS) isoform involved, which could play opposite roles in epileptogenesis, one of them being proconvulsant but the other anticonvulsant. The effect of convulsant drugs on neuronal NO (nNO) and endothelial NO (eNO) levels was investigated. Considering the distribution of neuronal and endothelial NOS in neurons and astrocytes, resp., primary cultures of neurons and astrocytes were used as a study model. The effects of convulsant drugs pentylenetetrazole, thiosemicarbazide, 4-aminopyridine and bicuculline on NO levels were studied, using a spectrophotometric method. Their effects on NO levels in neurons and astrocytes depend on the concentration and time of treatment. These convulsant drugs caused an increase in nNO, but a decrease in eNO was proportional to the duration of treatment in both cases. Apparently, nNO possesses convulsant properties mediated by its effect on the glutamatergic and GABAergic systems, probably through GABAA receptors. Anticonvulsant properties of eNO may be the consequence of its effect on endothelial vasodilation and its capability to induce angiogenesis. Described effects last as seizures do. Considering the limitations of these kinds of studies and the unexplored influence of inducible NO, further investigations are required