Effect of combined nitrogen on symbiotic nitrogen fixation in pea plants

The nitrogen-fixing activity of the symbiotic system of Pisum sativum with Rhizobium leguminosarum is adversely affected by combined nitrogen. Both ammonium chloride and potassium nitrate, when added to the roots, lower the nitrogenase activity (acetylene-reduction) of intact pea plants. During a 3-day treatment of the plants with combined nitrogen, when the in vivo nitrogenase activity falls to less than 50%, the nitrogenase activity of isolated bacteroids, treated with toluene and supplied with ATP and reductants, does not decrease. Thus, the potential nitrogenase activity of the root nodules is unaffected by short-term combined-nitrogen treatment of the plants. The adverse effect of ammonium chloride on the nitrogenase activity of pea plants is counteracted by the addition of sucrose or of methionine sulfoximine (an inhibitor of ammonia assimilation) to the rooting medium. A higher light intensity also diminishes the effect of ammonium chloride on nitrogenase activity.Ammonium chloride has no specific inhibitory effect on the nitrogenase activity of isolated pea bacteroids, neither in the anaerobic, nor in the aerobic assay. On the other hand, ammonium chloride does inhibit the nitrogenase activity of detached root nodules within a few hours. At a lower oxygen concentration in the assay this inhibition is more pronounced. The effect of ammonium chloride on detached nodules is relieved by simultaneous addition of methionine sulfoximine.Various carbon compounds (glucose and tricarboxylic acid cycle intermediates) stimulate the nitrogenase activity of detached nodules; only dicarboxylic acids of the tricarboxylic acid cycle support the nitrogenase activity of isolated bacteroids. Efficiencies of nitrogen fixation as to consumption of carbon compound are similar in both system , although lower than in the intact system. Ammonium chloride does not affect respiratory activities of detached nodules or of isolated bacteroids.It is concluded from the above-mentioned results that combined nitrogen, added to intact plants or detached nodules, does not affect nitrogenase activity directly. The results support the photosynthate theory, i.e. the photosynthate supply of the nodules is reduced and consequently the nitrogenase activity decreased, owing to the consumption of carbon compounds for the assimilation of the added combined nitrogen

Influence of ammonium chloride on the nitrogenase activity of nodulated pea plants (Pisum sativum).

A study was made on the short-term effect of ammonium ions on the nitrogenase activity of pea root nodules. Nodulated pea plants (Pisum sativum), having reached maximum acetylene-reducing activity, were supplied with NH4Cl (20 mM). Nitrogenase activity of intact plants, detached nodules, and isolated bacteroids was measured at differed time intervals. A significant drop (20 to 40%) in the acetylene-reducing activity of treated intact plants and their detached nodules was observed after 1 day. No drop in the nitrogenase activity of bacteroids (assayed aerobically, or anaerobically after treatment with ethylenediaminetetraacetic acid-toluene) occurred for 2 to 4 days after the addition of NH4+ to the plants, depending on cultural conditions. From these results it is concluded that the adverse effect of NH4+ on acetylene reduction by intact plants and detached nodules during the first 2 days is not due to a decrease in the amount of nitrogenase in the bacteroids. It is suggested that the effect has to be attributed to a reduced supply to the bacteroids of energy-delivery photosynthates

Effect of Ammonium Chloride and Methionine Sulfoximine on the Acetylene Reduction of Detached Root Nodules of Peas (Pisum sativum)

Acetylene-reducing activity of detached pea nodules was determined by submerging the nodules in buffer solution [tris(hydroxymethyl)aminomethane-hydrochloride, pH 7.4] containing 100 mM sodium succinate and incubating under a gas phase of 90% O(2) and 10% C(2)H(2). The nitrogenase activity was 4 to 8 μmol of C(2)H(4) formed per g of nodule fresh weight per h and remained constant for at least 4 h. Addition of NH(4)Cl to the buffer solution (at a concentration of 10 mM or more) resulted in a significant decrease of nitrogenase activity, which was more pronounced at higher concentrations of ammonium chloride. The inhibition of nitrogenase activity by NH(4)Cl was reversible; when the NH(4)Cl-containing buffer solution was replaced by buffer without NH(4)Cl, the original activity was partly restored. Treatment of the nodules with NH(4)Cl had almost no effect on the amount of nitrogenase, as measured by the acetylene-reducing activity of ethyl-enediaminetetraacetate-toluene-treated bacteroid suspensions. The effect of NH(4)Cl was largely eliminated by simultaneous addition of 10 mM methionine sulfoximine to the assay solution. This suggests that the assimilation of ammonium ions by glutamine synthetase controls the functioning of nitrogenase activity in the nodules. However, no effect of glutamine, glutamate, or aspartate on the acetylene reduction by detached nodules could be detected

Turnover of nitrogenase and leghemoglobin in root nodules of Pisum sativum

Turnover rates of the two nitrogenase components and leghemoglobin in root nodules of pea plants nodulated with Rhizobium leguminosarum were determined with three different methods: 1, Kinetics of 35S incorporation into protein; 2, pulse-chase experiments; 3, chloramphenicol inhibition of bacteroid protein synthesis. Methods 1 and 3 revealed that the turnover rates of the two nitrogenase components and leghemoglobin are identical to the average rate of bacteroid and plant nodule protein turnover. The t 1 2 times of component I and II and leghemoglobin were about 2 days. Pulse-chase experiments with 35SO2- 4 appeared to be rather unsuitable for determination of turnover rates in pea root nodules

European Cancer Organisation Essential Requirements for Quality Cancer Care (ERQCC): Lung cancer

European Cancer Organisation Essential Requirements for Quality Cancer Care (ERQCC) are written by experts representing all disciplines involved in cancer care in Europe. They give patients, health professionals, managers and policymakers a guide to essential care throughout the patient journey. Lung cancer is the leading cause of cancer mortality and has a wide variation in treatment and outcomes in Europe. It is a major healthcare burden and has complex diagnosis and treatment challenges. Care must only be carried out in lung cancer units or centres that have a core multidisciplinary team (MDT) and an extended team of health professionals detailed here. Such units are far from universal in European countries. To meet European aspirations for comprehensive cancer control, healthcare organisations must consider the requirements in this paper, paying particular attention to multidisciplinarity and patient-centred pathways from diagnosis, to treatment, to survivorship