Effects Of Nitrate Nutrition Research Articles

Effects of Nitrate Nutrition on Nitrogen Metabolism in Cassava

Two experiments were conducted independently with plants of cassava (Manihot esculenta Crantz) growing in sand with nutrient solutions with four nitrate concentrations (0.5, 3, 6 or 12 mM). In leaves, nitrate-N was undetectable at the low nitrate applications; total-N, ammonium-N, amino acid-N, reduced-N and insoluble-N all increased linearly, while soluble proteins did it curvilinearly, with increasing nitrate supply. In contrast, soluble-N did not respond to N treatments. Total-N and soluble proteins, but not nitrate-N or ammonium-N, were much higher in leaves than in roots. Plants grown under severe N deficiency accumulated ammonium-N and amino acid-N in their roots. Further, plants were exposed to either 3 or 12 mM nitrate-N, and leaf activities of key N-assimilating enzymes were evaluated. Activities of nitrate reductase, glutamine synthetase, glutamate synthase and glutamate dehydrogenase were considerably lower in low nitrate supply than in high one. Despite the low nitrate reductase activity, cassava leaves showed an ability to maintain a large proportion of N in soluble proteins.

Mineral nutrient status of corn in relation to nitrate and long‐term waterlogging

The effect of nitrate nutrition and long‐term waterlogging on the pattern of accumulation of inorganic nutrients in different plant organs was studied in corn (Zea mays L.) in glasshouse conditions. Continuous flooding of soils with NO3 added for 21 days, caused a complete depletion of NO3, but in turn NH4‐N increased significantly in these soils. Potassium (K) and phosphorus (P) contents in the flooded soils also increased whereas calcium (Ca) and magnesium (Mg) contents remained unaffected. Iron (Fe) and manganese (Mn) contents increased manifold as a result of flooding. Long‐term flooding caused a marked reduction in dry weight of both shoots and roots, and supplementary NO3‐N exacerbated the inhibitory effect of waterlogging on plant growth. A considerable decrease in nitrogen (N), P, and K contents in leaves was observed as a result of flooding, whereas in roots the reverse was true. However, N and P contents under waterlogged conditions increased consistently with an increase in the applied NO3 level. Flooding caused a marked reduction in Ca in both leaves and roots, and Mg only in leaves. Enhanced soil NO3‐N had no effect on the concentration of Ca and Mg in leaves or roots. Concentrations of Fe and Mn in leaves and roots increased significantly due to continuous flooding, but a marked increase in these two nutrients was observed in roots. Addition of NO3‐N to the waterlogged soils caused a slight increase in Fe in both leaves and roots but did not affect the Mn content in leaves or roots. Supplementary NO3‐N was inhibitory to corn growth under long‐term hypoxic conditions, particularly, the two higher concentrations (294 and 392 mg NO3‐N kg−1 soil).

The effect of nitrate nutrition on iron chlorosis and leaf growth in sunflower ( Helianthus annuus L.)

The objective of this work was to investigate the effects of nutrient solution pH, nitrogen form (NO 3, NH 4NO 3), bicarbonate and different Fe concentrations in the nutrient solution on the Fe concentration in roots and on the development of Fe deficiency symptoms in sunflower plants ( Helianthus annuus L.). High pH in the nutrient solution induced by nitrate supply or by a pH-stat device led to increased Fe concentrations in roots and low leaf Fe concentrations associated with a significant decrease in leaf chlorophyll concentration manifested by yellow leaves. Plants of the nitrate fed treatments with 1 μM Fe in the nutrient solution were also characterized by reduced leaf growth and by the suppression of new leaf formation. The reduced leaf growth and the suppression of new leaves only occurred with nitrate and not with NH 4NO 3 in all treatments with 1 μM Fe in the nutrient solution. All symptoms were removed by a high Fe concentration in the nutrient solution (100 μM) at low external pH proving that suppression of leaf formation, reduced leaf growth and low chlorophyll concentration were caused by Fe deficiency. In the nitrate treatment with a low Fe supply (1 μM Fe) and pH 4 in the nutrient solution leaf chlorophyll concentrations similar to the controls were found. In comparison to control plants (NH 4NO 3, 1 μM Fe), leaf growth was still significantly reduced, and new leaf formation was suppressed. The chlorophyll concentration and CO 2 assimilation rate did not differ from those of the control plants. These results show that Fe deficiency is also characterized by small green leaves and the suppression of leaf formation. At the onset of leaf development, leaf growth and new leaf formation may respond more sensitively to poor Fe efficiency than chlorophyll concentration. In experiments with NO 3 plus HCO 3, simulating soil solution conditions prevailing in calcareous soils, the Fe efficiency of the youngest leaves was poor, showing retarded leaf growth and low chlorophyll concentration.

Nitrogen dioxide and nitrate nutrition effects on nitrate reductase activity and nitrate content of bean leaves

The increase in in vivo nitrate reductase activity and nitrate content in leaves of 10-day-old bean plants ( Phaseolus vulgaris cv. Kinghorn Wax) supplied with 10 mM nitrate for up to 24 hr was compared to that of plants supplied with 0.5 μl/l NO 2 gas. Both nitrogen sources caused an increase in enzyme activity over time but only nitrate supplied leaves had an increased leaf nitrate concentration over the same time period. Inhibitors of the nitrate assimilation pathway, such as tungstate and methionine sulfoximine, inhibited the increase in nitrate reductase activity and nitrate content, an inhibition which was more apparent in the presence of nitrate than of NO 2. The effect of albizzine was insignificant, except for nitrate reductase activity in nitrate supplied leaves. It is suggested that nitrate generated from NO 2 is metabolized more rapidly than that from nutrient nitrate.

Effect of nitrate nutrition on iron utilization by an Fe-efficient and an Fe-inefficient soybean cultivar

The effects of increasing amount of nitrate nitrogen on the growth, dry matter production, ionic balance and the appearance of iron chlorosis in two soybean cultivars were studied. More nitrogen increased the dry matter production of the Fe-efficient cultivar Hawkeye and decreased that of the Fe-inefficient cultivar T-203. The plants of Hawkeye showed no iron deficiency symptoms whereas all the plants of the Fe-inefficient cultivar T-203 developed Fe deficiency after about one week following emergence. The degree of chlorosis in the cultivar T-203 was more pronounced as the amount of nitrate applied increased.