Dr. Raman et al., THE KINETICS OF NITRATE UPTAKE FROM FLOWING SOLUTIONS BY RICE - INFLUENCE OF PRETREATMENT AND LIGHT, Bioresource technology, 53(2), 1995, pp. 125-132
Citations number
36
Categorie Soggetti
Energy & Fuels","Biothechnology & Applied Migrobiology",Agriculture
The kinetics of nitrate (NO3-) uptake by intact 23 day old lice plants
was studied by measuring the depletion of NO3- in solutions flowing o
ver the plant roots. A Michaelis-Menten kinetic model was applied allo
wing the uptake kinetics to be characterized by two parameters: the ap
parent half-velocity constant, K-m, and the apparent maximum uptake ra
te, V-max A propagation of uncertainty calculation revealed that the k
inetic parameters could be determined with a high degree of accuracy;
the standard deviation in K-m was typically 15% of the K-m value; the
standard deviation in V-max was typically 7% of the V-max value. The p
lants were exposed to full nutrient solutions containing NO3- at 50, 2
00, 500 and 800 mu M for 24 h prior to kinetic testing, and both K-m a
nd V-max were found to vary with pretreament NO3- concentration, [NO3-
]; plants pretreated at high [NO3-] had lower V-max and higher K-m val
ues than plants pretreated at lower [NO3-]. However tile variations in
V,, were more consistent than those in K-m. These changes in the kine
tic parameters reflect an uptake system which is capable of compensati
ng for changes in the external [NO3-] to maintain a virtually constant
NO3- uptake rate in the range studied. Changes in K-m and V-max begin
within 4 h of a change in [NO3-]. Light deprivation during pretreatme
nt in 200 mu M NO3- resulted in a complete cessation of NO3- uptake; 4
-8 h of illumination were required before the uptake resumed, and upta
ke rates had not yet reached normal levels 8 h after the resumption of
illumination.