Summary• The aim of the paper was to determine nitrogen compounds contributing to leaf cell osmoregulation of spinach ( Spinacia oleracea ) submitted to increasing salt stress.• Sodium, free amino acids and glycine betaine contents were determined in the last fully expanded leaf of plants stressed by daily irrigation with saline water (0.17 M NaCl).• After 20 d of treatment, when Na + content was c . 55 umol g − 1 f. wt above the control, and the reduction of stomatal conductance lowered photosynthesis to c . 60% of the control, the free amino acids of the leaves, especially glycine and serine, strongly increased. Proline and glycine betaine also increased significantly. After 27 d of treatment, when the Na + content was c . 100 umol g − 1 f. wt above the control and photosynthesis was 33% of the control, the free amino acid content, especially glycine and serine, declined. Gycine betaine, but not proline, increased further.• Glycine betaine comprised c . 15% of the overall nitrogen osmolytes at mild saltstress, but represented 55% of the total, when the stress became more severe. The increase of glycine betaine balanced the decline in free amino acids, mainly replacing glycine and serine (the precursors of glycine betaine) in the osmotic adjustment of the cells. Photorespiration, which increased during salt stress, was also suggested to have a role in supplying metabolites to produce compatible osmolytes.

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In order to ascertain whether oxidative phosphorylation in plant mitochondria is sensitive to light, coupled durum wheat (Triticura durum Desf.) mitochondria were irradiated with a low power continuous wave Helium-Neon laser (fluence: 2 Joules/cm2), with measurements made of certain processes related to ATP production. As a result of irradiation, an increase in the rate of ATP synthesis was found, as continuously monitored via luciferine/luciferase, moreover the mitochondrial ATP and ADP endogenous contents were found to increase and decrease, respectively with a 1:1 stoichiometry, as revealed by HPLC measurements. Consistently, an increase in mitochondrial rate of A~I/generation was found as measured by using the fluorescent probe safranine. Thus, this paper gives a first evidence of a novel property of plant mitochondria: the direct light sensitivity of ATP synthesis via oxidative phosphorylation.

Abiotic stresses, such as high salinity or drought, can cause proline accumulation in plants. Such an accumulation involves proline transport into mitochondria where proline catabolism occurs. By using durum wheat seedlings as a plant model system, we investigated how proline enters isolated coupled mitochondria. The occurrence of two separate translocators for proline, namely a carrier solely for proline and a proline/glutamate antiporter, is shown in a functional study in which we found the following: (1) Mitochondria undergo passive swelling in isotonic proline solutions in a stereospecific manner. (2) Externally added L: -proline (Pro) generates a mitochondrial membrane potential (Delta Psi) with a rate depending on the transport of Pro across the mitochondrial inner membrane. (3) The dependence of the rate of generation of Delta Psi on increasing Pro concentrations exhibits hyperbolic kinetics. Proline transport is inhibited in a competitive manner by the non-penetrant thiol reagent mersalyl, but it is insensitive to the penetrant thiol reagent N-ethylmaleimide (NEM). (4) No accumulation of proline occurs inside the mitochondria as a result of the addition of proline externally, whereas the content of glutamate increases both in mitochondria and in the extramitochondrial phase. (5) Glutamate efflux from mitochondria occurs at a rate which depends on the mitochondrial transport, and it is inhibited in a non-competitive manner by NEM. The dependence of the rate of glutamate efflux on increasing proline concentration shows saturation kinetics. The physiological role of carrier-mediated transport in the regulation of proline catabolism, as well as the possible occurrence of a proline/glutamate shuttle in durum wheat seedlings mitochondria, are discussed.

Wireless Sensor Networks (WSNs) are widely recognized as a promising solution to build next-generation monitoring systems. Their industrial uptake is however still compromised by the low level of trust on their performance and dependability. Whereas analytical models represent a valid mean to assess nonfunctional properties via simulation, their wide use is still limited by the complexity and dynamicity of WSNs, which lead to unaffordable modeling costs. To reduce this gap between research achievements and industrial development, this paper presents a framework for the assessment of WSNs based on the automated generation of analytical models. The framework hides modeling details, and it allows designers to focus on simulation results to drive their design choices. Models are generated starting from a high-level specification of the system and by a preliminary characterization of its fault-free behavior, using behavioral simulators. The benefits of the framework are shown in the context of two case studies, based on the wireless monitoring of civil structures

Cyanidium caldarium (Tilden) Geitler, a non‐vacuolate unicellular alga, resuspended in medium flushed with air enriched with 5% CO2, assimilated NH4+ at high rates both in the light and in the dark. The assimilation of NO3−, by contrast, was inhibited by 63% in the dark. In cell suspensions flushed with CO2‐free air, NH4+ assimilation decreased with time both in the light and in the dark and ceased almost completely after 90 min. The addition of CO2 completely restored the capacity of the alga to assimilate NH4+. NO3− assimilation, by contrast, was 33% higher in the absence of CO2 and was linear with time. It is suggested that NO3− and NH4+ metabolism in C. caldarium are differently controlled in response to the light and carbon conditions of the cell.

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