Nitrate reductase and glutamine synthetase activities in relation to growth and nitrogen assimilation in red oak and red ash seedlings: effects of N-forms, N concentration and light intensity

Trees ◽  
1994 ◽  
Vol 9 (1) ◽  
Author(s):  
Benoit Truax ◽  
France Lambert ◽  
Daniel Gagnon ◽  
Normand Chevrier
Keyword(s):  
Light Intensity ◽  
Nitrate Reductase ◽  
Glutamine Synthetase ◽  
Nitrogen Assimilation ◽  
Red Oak ◽  
N Concentration

scholarly journals Nitrogen assimilation in orchids

HortScience ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 680f-680
Author(s):  
C.S. Hew ◽  
L.Y. Lim ◽  
C.M. Low
Keyword(s):  
Nitrate Reductase ◽  
Glutamine Synthetase ◽  
Ammonium Nitrate ◽  
Nitrate Uptake ◽  
Nitrogen Assimilation ◽  
Solution Culture ◽  
Ion Uptake ◽  
Ammonium Uptake ◽  
Regulatory Role ◽  
Epiphytic Orchids

The uptake of nitrate and ammonium by a terrestial (Bromheadia finlaysonia) and an epiphytic (Dendrobium hybrid) orchid in solution culture has been studied. The rates of nitrate and ammonium were relatively linear, with higher rate of uptake for ammonium. The rates of nitrate uptake in terrestial and epiphytic orchids were 0.4 and 0.9 μmole gm fw-1 hr-1 respectively and they were considerably lower than those of most major crops. SEM studies show that the velamen of Bromheadia was 2 cells thick whereas that of Dendrobium was 8-10 cells thick. It is unlikely that the velamen is the major factor in restricting influx of nitrate or ammonium. Nitrate reductase (NR) and glutamine synthetase (GS) were present in roots and leaves of both orchids. NR was high in roots but low in leaves. The reverse was for GS. The activities of NR and GS was low but high enough to account for the rate of nitrate or ammonium uptake. It appears that the movement of ions across the transfer junction at the exodermis plays a major regulatory role in ion uptake by orchid root.

scholarly journals Nitrogen Assimilation of Micropropagated Strawberry Plantlets during the Transition from Heterotrophy to Photoautotrophy

HortScience ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 871A-871
Author(s):  
S. Aquin ◽  
Y. Desjardins ◽  
L.-P. Vézina
Keyword(s):  
Nitrate Reductase ◽  
Glutamine Synthetase ◽  
Nitrogen Metabolism ◽  
Nitrate Reduction ◽  
Nitrogen Assimilation ◽  
Culture Period ◽  
Leaf Tissues ◽  
Root Tissues ◽  
Nr Activity ◽  
Different Tissues

A study was conducted to determine the implication of nitrate reductase (NR) and glutamine synthetase (GS) during the transition of micropropagated plantlets from heterotrophy to photoautotrophy to document how nitrogen metabolism interfaces with photosynthetic and anaplerotic CO2 fixation. The activity of the two enzymes was determined in different tissues at different organogenic stages during the development of plantlets transferred onto rooting media containing varying quantities of sucrose. Under 3% sucrose, NR activity was much higher in leaves than in crown tissues. When roots are initiating, there is a shift in the proportion of nitrate reduction from leaves to crown. As roots mature, the proportion of nitrate reduction increases in roots. Similar trends were observed under 5% sucrose. In contrast, under 1% sucrose, a higher proportion of the nitrate is reduced in the leaf tissues throughout the culture period. This suggests that nitrate is reduced mainly in leaves in photoautotrophic plantlets, while it is reduced in crowns and root tissues for mixotrophic plantlets. In general, the GS activity follows the pattern of NR, but is always in excess, to enable rapid assimilation of ammonium derived from metabolism and medium absorption.

Control of nitrogen assimilation in Stichococcus bacillaris by growth conditions

1987 ◽  
Vol 65 (3) ◽  
pp. 432-437 ◽  
Author(s):  
Iftikhar Ahmad ◽  
Johan A. Hellebust
Keyword(s):  
Glutamine Synthetase ◽  
Nitrogen Assimilation ◽  
Continuous Light ◽  
Synthetase Activity ◽  
Glutamine Synthetase Activity ◽  
Dark Cycle ◽  
Continuous Darkness ◽  
Cell Carbon ◽  
Stichococcus Bacillaris ◽  
Mixotrophic Conditions

Stichococcus bacillaris Naeg. (Chlorophyceae) grown on a 12 h light: 12 h dark cycle divides synchronously under photoautotrophic conditions and essentially nonsynchronously under mixotrophic conditions. Photoassimilation of carbon under photoautotrophic conditions was followed by a decline in cell carbon content during the dark period, whereas under mixotrophic conditions cell carbon increased throughout the light–dark cycle. The rates of nitrogen assimilation by cultures grown on either nitrate or ammonium declined sharply during the dark, and these declines were most pronounced under photoautotrophic conditions. Photoautotrophic cells synthesized glutamine synthetase and NADPH – glutamate dehydrogenase (GDH) exclusively in the light, whereas in mixotrophic cells about 20% of the total synthesis of these enzymes during one light–dark cycle occurred in the dark. NADH–GDH was synthesized almost continuously over the entire light–dark cycle. In the dark, both under photoautotrophic and mixotrophic conditions, the alga contained more than 50% of glutamine synthetase in an inactive form, which was reactivated in vitro in the presence of mercaptoethanol and in vivo after returning the cultures to the light. The thermal stability of glutamine synthetase activity was less in light-harvested cells than in dark-harvested cells. The inactivation of glutamine synthetase did not occur in cultures growing either heterotrophically in continuous darkness or photoautotrophically in continuous light. This enzyme appears to be under thiol control only in cells grown under alternating light–dark conditions, irrespective of whether this light regime results in synchronous cell division or not.

Nitrogen assimilation and dissimilation in five genotypes of Brachiaria spp.

1981 ◽  
Vol 59 (8) ◽  
pp. 1475-1479 ◽  
Author(s):  
Pedro Antonio A. Pereira ◽  
Johanna Döbereiner ◽  
Carlos A. Neyra
Keyword(s):  
Nitrate Reductase ◽  
Field Experiment ◽  
Nitrogen Assimilation ◽  
Nitrogenase Activity ◽  
Nitrate Accumulation ◽  
Brachiaria Ruziziensis ◽  
Intact Soil ◽  
Nr Activity ◽  
Better Than ◽  
Nitrate Fertilization

Five genotypes of Brachiaria spp. were planted in a field experiment with and without nitrate fertilization. Nitrogen metabolism was evaluated by measurements of nitrate reductase (NR) activity in leaves, nitrate accumulation in stems, and nitrogenase activity and dentrification in intact soil–plant cores. There were differences between genotypes in all parameters and a tendency was observed for genotypes with high NR activity and nitrate accumulation to have low nitrogenase activity and vice versa. Brachiaria radicans (Tanner grass) was representative for the first type and B. ruziziensis (CPI 30623) for the second. Denitrification reached 7% of the applied N within 63 h and was lowest in Tanner grass and highest in B. brizantha (FL 902-4). Brachiaria ruziziensis (CPI 30623) plants were able to withstand N stress better than B. radicans as a consequence, possibly, of differences in nitrogenase activity.

Influences of light intensity on weed-induced stresses of tree seedlings

1990 ◽  
Vol 20 (5) ◽  
pp. 503-507 ◽  
Author(s):  
T. E. Kolb ◽  
T. W. Bowersox ◽  
L. H. McCormick
Keyword(s):  
Soil Moisture ◽  
Light Intensity ◽  
Tree Species ◽  
Red Oak ◽  
Tree Seedlings ◽  
Northern Red Oak ◽  
White Pine ◽  
White Ash ◽  
Reduced Height ◽  
Four Levels

Growth of northern red oak (Quercusrubra L.), white ash (Fraxinusamericana L.), and white pine (Pinusstrobus L.) seedlings was evaluated for 2 years after germination in 12 environments that consisted of four levels of herbaceous interference (fern, fern free, grass, grass free) crossed with three levels of light intensity (100, 45, and 20% full sun), at two clear-cuts in central Pennsylvania. Grass and fern interference reduced soil moisture content and reduced height or diameter growth of all species. Shading ameliorated soil moisture, reduced herbaceous growth, generally reduced growth of all tree species in interference-free environments, and had no effect on growth of any tree species in fern and grass environments. Reduction in growth due to herbaceous interference was lower for northern red oak and white pine than for white ash, while shading had similar effects on growth of all species. Results suggest that stresses induced by shading alone have little short-term effect on the establishment of these species under conditions of heavy herbaceous interference.

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