New Zealand Journal of Agricultural Research abstracts
In vivo nitrate reductase activity in ryegrass (Lolium perenne)
and white clover (Trifolium repens): differences due to nitrogen supply,
development, and plant part
M. L. Castle*
J. S. Rowarth†
Soil, Plant and Ecological Sciences Division
Lincoln University
P.O. Box 84
Lincoln
Canterbury, New Zealand
email: maria.castle@agResearch.co.nz
*Present address: Plant Breeding and Genomics, AgResearch, Private Bag 3123,
Hamilton, New Zealand.
†Present address: UNITEC, Private Bag 92 025, Auckland, New Zealand.
Abstract Differences in response to nitrogen (N) exhibited
by different plants might be explained by nitrate reductase activity (NRA),
but drawing conclusions about NRA is difficult because of the large range
in NRA, and the variation in sampling techniques reported in the literature.
This experiment was established to determine a sampling regime for ryegrass
and white clover which would allow the effect of experimental treatments
to be observed. Ryegrass and white clover were grown in sand culture in a
glasshouse. Plants were supplied with a complete nutrient solution containing
either a low-N (0.5 mol m-3) or high-N (5.0 mol m-3)
concentration. NRA was assessed weekly, for 8 weeks. Ryegrass was separated
into leaf blades, sheaths, and roots; white clover was separated into laminae,
petioles, and roots. In both species, NRA decreased (P < 0.05) with time
and was greater in the high-N treatment than the low-N treatment. Ryegrass
had significantly (P < 0.05) less NRA than white clover (1.32 cf. 2.20
µmol NO2- gfwt -1 h-1,
respectively), and at most harvests there was significantly (P < 0.05)
more in vivo NRA in the leaf sheaths than in the blades or roots. In white
clover, there was significantly (P < 0.05) more NRA in the roots than
in the petioles or laminae. In both species, analysing components of plants
separately at 6 weeks resulted in most sensitivity for in vivo NRA analysis.
Keywords development; Lolium perenne; morphology;
nitrate reductase (NR); ryegrass; Trifolium repens; white clover
A02042 Received 15 July 2002; accepted 19 December 2002; published 26
March 2003
New Zealand Journal of Agricultural Research, 2003, Vol. 46: 31-36
0028-8233/03/4601-0031 $7.00/0 © The Royal Society of New Zealand
2003
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