Low Nitrate Reductase Activity Research Articles

Nitrogen Metabolism in the Height Forms of Spartina Alterniflora in North Carolina

Selected aspects of the nitrogen nutrition of salt marsh cordgrass, Spartina alterniflora, were investigated in Oak Island Marsh, North Carolina, USA. Nitrate was of minor importance as a nitrogen source for Spartina in this marsh as indicated by low soil interstitial water nitrate concentrations and low plant tissue nitrate concentrations and nitrate reductase activities. However, Spartina did have the capability of assimilating nitrate nitrogen when available. Interstitial water and plant tissue ammonium concentrations were 1—2 orders of magnitude > that for nitrate which strongly indicated that ammonium was the dominant inorganic nitrogen source. Leaf and root nitrogen constituents (total nitrogen, soluble nitrogen, ammonium, and nitrate) and nitrogen metabolism measured via glutamate dehydrogenase activity indicated that the nitrogen status of the short height form of Spartina was deficient relative to that of the tall form.

Nitrate assimilation enzymes from two hard corals, Acropora acuminata and Goniastrea australensis

1. 1. The enzymes required for assimilatory nitrate reduction were present in crude preparations from zooxanthellae. 2. 2. Relatively high activities of nitrate reductase and glutamate dehydrogenase were determined. 3. 3. The low nitrate reductase activity probably resulted from denaturation of the enzyme in vitro and factors associated with enzyme extraction. 4. 4. Nitrate reductase was induced by light and exogenous nitrate.

Effect of ammonium nutrition on uptake and metabolism of nitrate in wheat.

Wheat plants 1 month old grown in nitrate culture were exposed for 2 days to media containing 4 meq NO3 and 0-4 meq NH4/l. Where solutions contained both forms of N the uptake of NH4 exceeded that of NO3 even at the lowest NH4 level. NH4 metabolism predominated over NO3 assimilation and resulted in a higher free amino acid content, a lower carboxylate content and lower nitrate reductase activity in the tops than with NO3 alone. NH4 inhibited nitrate reductase activity whereas amino acids did not. The fall in activity of this enzyme in wheat tops caused by NH4 nutrition could not be related to the low level of tissue NH4 and it was suggested that changes in the redox situation in the cells might be involved. (Abstract retrieved from CAB Abstracts by CABI’s permission)

EFFECTS OF NITROGEN NUTRITION AND DAY TEMPERATURE ON COMPOSITION, COLOR AND NITRATE IN TOMATO FRUIT

The effects of nitrogen nutrition and day temperature on composition, color and nitrate in VF–145 tomatoes were investigated in growth chambers kept at 20, 25, 30 and 35°C respectively during the days for 14 hr, and at 20° C during the nights for 10 hr. Nitrogen fertilizer application was altered in half the pots in each chamber by supplying them with half‐strength −N Hoagland's #1 solution during the fruit growth period. Tomatoes from fertilized plants (+N) were slightly higher in titratable acidity but lower in solids content than those from the −N plants. Fruits ripening at high day temperature were poor in color while those ripening at below 30°C were more attractive in color. The total, amino, ammonium and nitrate nitrogen contents of the tomato fruits were higher in the +N series than those of –N series. Tomatoes from plants receiving +N treatments contained more nitrate than those receiving −N treatments. Day temperature greatly affected the nitrate content in the tomatoes. In the +N series the nitrate content of the tomatoes decreased from 72.9 ppm to 0.37 ppm as the day temperature increased from 20: to 35°C. In the −N series, the nitrate content ranged from 0.35–1.15 ppm. Accumulation of nitrates in tomatoes appears to be related to the level of nitrate in the nutrient solution and the day temperature. Low day temperature results in accumulation of nitrate because of the low nitrate reductase activity.

Accumulation of Nitrate in Tomato Fruit and its Effect on Detinning1,2

Abstract Tomato fruit accumulated nitrate when the controlled environmental conditions combined high temperature, high N fertilization level, and low light intensity. Nitrate accumulation in the fruit was preceded by a condition of low nitrate reductase activity and nitrate accumulation in the leaves. The processed product with high concentration of nitrate caused extensive detinning of internal can surfaces after 6 months’ storage at room temperature.

Nitrate reductase of rice (Oryza sativa L.) under foot-rot disease

Studies reported here reveal a low nitrate reductase activity in the shoots of MTU 9 rice plants while in roots high enzyme activity has been recorded.Under pathogenesis, a low nitrate reductase activity in the roots and a high enzyme activity in the shoots have been recorded in susceptible rice plants. In the resistant rice plants (GEB 24) no such marked difference in the enzyme activity has been observed.The effect of fusaric and gibberellic acid on this enzyme activity has been studied. In the case of fusaric acid, the nitrate reductase activity in the roots is inversely proportional to the concentration whereas in gibberellic acid, it is directly proportional to the concentration in the shoots.