TY - JOUR
T1 - The nitrogen balance of Raphanus sativus X raphanistrum plants. I. Daily nitrogen use under high nitrate supply
AU - SCHULZE, E. ‐D
AU - Koch, George W
AU - PERCIVAL, F.
AU - MOONEY, H. A.
AU - CHU, C.
PY - 1985/12
Y1 - 1985/12
N2 - Abstract Growth‐chamber cultivated Raphanus plants accumulate nitrate during their vegetative growth. After 25 days of growth at a constant supply to the roots of 1 mol m−3 (NO−3) in a balanced nutrient solution, the oldest leaves (eight‐leaf stage) accumulated 2.5% NO−3‐nitrogen (NO3‐N) in their lamina, and almost 5% NO3‐N in their petioles on a dry weight basis. This is equivalent to approximately 190 and 400 mol−3 m−3 concentration of NO−3 in the lamina and the petiole, respectively, as calculated on a total tissue water content basis. Measurements were made of root NO−3 uptake, NO−3 fluxes in the xylem, nitrate uptake by the mesophyll cells, and nitrate reduction as measured by an in vivo test. NO−3 uptake by roots and mesophyll cells was greater in the light than in the dark. The NO−3 concentration in the xylem fluid was constant with leaf age, but showed a distinct daily variation as a result of the independent fluxes of root uptake, transpiration and mesophyll uptake. NO−3 was reduced in the leaf at a higher rate in the light than in the dark. The reduction was inhibited at the high concentrations calculated to exist in the mesophyll vacuoles, but reduction continued at a low rate, even when there was no supply from the incubation medium. Sixty‐four per cent of the NO−3 influx was turned into organic nitrogen, with the remaining NO−3 accumulating in both the light and the dark.
AB - Abstract Growth‐chamber cultivated Raphanus plants accumulate nitrate during their vegetative growth. After 25 days of growth at a constant supply to the roots of 1 mol m−3 (NO−3) in a balanced nutrient solution, the oldest leaves (eight‐leaf stage) accumulated 2.5% NO−3‐nitrogen (NO3‐N) in their lamina, and almost 5% NO3‐N in their petioles on a dry weight basis. This is equivalent to approximately 190 and 400 mol−3 m−3 concentration of NO−3 in the lamina and the petiole, respectively, as calculated on a total tissue water content basis. Measurements were made of root NO−3 uptake, NO−3 fluxes in the xylem, nitrate uptake by the mesophyll cells, and nitrate reduction as measured by an in vivo test. NO−3 uptake by roots and mesophyll cells was greater in the light than in the dark. The NO−3 concentration in the xylem fluid was constant with leaf age, but showed a distinct daily variation as a result of the independent fluxes of root uptake, transpiration and mesophyll uptake. NO−3 was reduced in the leaf at a higher rate in the light than in the dark. The reduction was inhibited at the high concentrations calculated to exist in the mesophyll vacuoles, but reduction continued at a low rate, even when there was no supply from the incubation medium. Sixty‐four per cent of the NO−3 influx was turned into organic nitrogen, with the remaining NO−3 accumulating in both the light and the dark.
KW - Raphanus
KW - nitrate accumulation
KW - nitrate reduction
KW - nitrate transport
KW - nitrate uptake
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U2 - 10.1111/1365-3040.ep11611835
DO - 10.1111/1365-3040.ep11611835
M3 - Article
AN - SCOPUS:84981632130
SN - 0140-7791
VL - 8
SP - 713
EP - 720
JO - Plant, Cell & Environment
JF - Plant, Cell & Environment
IS - 9
ER -