scholarly journals Partitioning of nitrate reductase activity in Coffea arabica L. and its relation to carbon assimilation under different irradiance regimes

2006 ◽  
Vol 18 (3) ◽  
pp. 397-406 ◽  
Author(s):  
Maria Luiza C. Carelli ◽  
Joel I. Fahl

The distribution of in vivo nitrate reductase (EC 1.6.6.1) activity (NRA) between leaves and roots was studied in young coffee plants (Coffea arabica L.) grown in pots with watered sand in a glasshouse and irrigated with nutrient solution. The influence of irradiance regimes on the partitioning of NRA, and its relation with CO2 assimilation, was also evaluated in plants grown under approximately 20, 50 and 100% of full sunlight. Time-course of nitrate accumulation in nitrogen-starved plants showed a similar pattern in leaves and roots after supplying 15 mmol L-1 nitrate, indicating efficient ability of the roots to export nitrate to the shoot. At the same time, NRA was rapidly induced in both tissues. In shoots, NRA partitioning was synchronized among the various leaf pairs. The initial increase in NRA, as each leaf pair emerged, coincided with the optimum NRA values of the next older leaf pair. However, the average shoot NRA remained relatively constant for each sampling date. During the first 23 weeks of vegetative growth, the mean NRA was 32% higher in leaves than in roots. The irradiance regimes influenced the partitioning of NRA between leaves and roots. The NRA leaf /root ratio was 0.72, 1.21 and 1.05, respectively, for plants grown under 20%, 50% and 100% of full sunlight. Leaf NRA was positively correlated with CO2 assimilation, in response to irradiance regimes. Under favorable CO2 assimilation conditions, higher NRA was observed in leaves than in roots, and the contrary trend occurred under limiting CO2 assimilation conditions. Under moderate irradiance regime the leaves were the main site of nitrate reduction, contributing with 70% of the whole plant nitrate assimilation.

1995 ◽  
Vol 94 (2) ◽  
pp. 305-311 ◽  
Author(s):  
Lucia Merlo ◽  
Massimo Ferretti ◽  
Calvino Passera ◽  
Rossella Ghisi

1986 ◽  
Vol 16 (6) ◽  
pp. 1165-1169 ◽  
Author(s):  
P. Högberg ◽  
A. Granström ◽  
T. Johansson ◽  
A. Lundmark-Thelin ◽  
T. Näsholm

The nitrate reductase activity of Deschampsiaflexuosa (L.) Trin., an evergreen grass species common in northern coniferous forests, was tested as an indicator of nitrate availability in forest soils. A positive linear correlation (correlation coefficient significantly different from zero, p < 0.01) was found between nitrate supply and nitrate reductase activity in shoots of seedlings in sand cultures. Throughout a vegetation period the nitrate reductase activity of D. flexuosa was constantly 2–16 times higher in a clear-cut area as compared with an adjacent forest. High enzyme activity, however, indicated significant amounts of nitrate also in the forest during spring and autumn. On plots heavily fertilized with urea the nitrate reductase activity was up to three times higher than on control plots, which suggests considerable nitrate formation on the former. The plant nitrate reductase activity method seemed to be an inexpensive, rapid, nondisturbing, semiquantitative indicator of nitrate availability in soils, particularly for time-course studies and in comparisons between experimental plots. Tests of maximal induction of nitrate reductase activity can reveal to what extent factors other than the supply of nitrate are limiting the activity.


2001 ◽  
Vol 13 (1) ◽  
pp. 66-74 ◽  
Author(s):  
JOSÉ A.T. AMARAL ◽  
FÁBIO M. DA MATTA ◽  
ALEMAR B. RENA

Active vegetative and reproductive growth in field-grown trees of Coffea arabica L. in Viçosa (20º45’S, 650 m altitude), south-eastern Brazil, occur concurrently. The overall patterns of branch growth and leaf area gain were to a certain extent altered by fruit removal, with growth rates being remarkably greater in de-fruited trees. The content of N-NO3 was not affected by fruiting, whilst that of amino-N was greater in de-fruited than fruiting trees most of the time, but the differences were not large enough to have significantly contributed to the increased growth rates in de-fruited trees. Leaf nitrate reductase activity was greater in plants bearing fruit than in non-bearing ones most of the time; activity was roughly inversely associated with growth. Although the roots contained much more nitrate than the leaves, the root nitrate reductase activity was much lower and not affected by fruiting. Much of the restrictive effects of fruiting on vegetative growth appeared to be associated to starch exhaustion, in addition to the outstanding effect of supra-optimum temperatures per se.


1995 ◽  
Vol 94 (2) ◽  
pp. 305-311 ◽  
Author(s):  
Lucia Merlo ◽  
Massimo Ferretti ◽  
Calvino Passera ◽  
Rossella Ghisi

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