Résumé
The study characterized the influence of cucumber mosaic virus
(CMV) on
the growth response of two annual
weeds to nitrogen. Plants were grown individually along a N gradient from
4 to 32 mmol
l−1 and data were
interpreted using growth analysis. Plant biomass increased with N concentration
and was significantly higher for
healthy than infected plants at the two highest N concentrations.
Healthy plants of Portulaca oleracea L. were
characterized by lower biomass allocation to leaves and higher biomass
allocation to roots than infected plants; no
change in biomass allocation was recorded for Stellaria media
Vill. Relative growth rate (rgr), net assimilation
rate (nar) and specific leaf area (sla) of plants
increased with increasing N concentration. Healthy plants of P.
oleracea were characterized by a higher rgr and nar
and a lower sla than infected plants, whereas healthy S. media
had a higher rgr but a similar nar and sla
or leaf weight ratio (lwr) compared with infected plants. The
consequences of these results on the population dynamics of weeds and virus
spread are discussed.