Effects of a stay-green mutation on plant nitrogen relations in Lolium perenne during N starvation and after defoliation.
The stay-green mutation of the nuclear gene sid results in inhibition of chlorophyll degradation during leaf senescence in grasses, reducing N remobilization from senescing leaves. Effects on growth of Lolium perenne L. were investigated during N starvation (over 18 d) and after severe defoliation, when leaf growth depends on the remobilization of internal N. Rates of dry mater production, partitioning between shoots and roots, and re-partitioning of N from shoots to roots were very similar in stay-green and normal plants under N starvation. Km and Vmax for net uptake of NH4+ were also similar for both genotypes, and Vmax increased with the duration of N deprivation. The mutation had little effect on recovery of leaf growth following severe defoliation, but stay-green plants recommenced NO3- and K+ uptake 1 d later than normal plants. Import of remobilized N into new leaves was generally similar in both lines. However, stay-green plants remobilized less N from stubble compared with normal plants. It was concluded that the sid locus stay-green mutation has no significant adverse effect on the growth of L perenne during N starvation, or recovery from severe defoliation when plants are grown under an optimal regime of NO3- supply both before and after defoliation. The absence of any effect on leaf dry matter production implies that the difference in foliar N availability attributable to this mutation has little bearing on productivity, at least in the short to medium term.
Macduff
J H
JH
Institute of Grassland and Environmental Research, Aberystwyth, Ceredigion, UK. james.macduff@bbsrc.ac.uk
Humphreys
M O
MO
Thomas
H
H
D000465:Algorithms; D005838:Genotype; D007700:Kinetics; D008129:Lolium / Q000187:drug effects / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D009154:Mutation; D009566:Nitrates / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism* / Q000494:pharmacology; D009587:Nitrogen Isotopes / Q000378:metabolism; D018515:Plant Leaves / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism
D009566:Nitrates; D009587:Nitrogen Isotopes; D000644:Quaternary Ammonium Compounds; D009584:Nitrogen; D011188:Potassium