Responses to shading in Chenopodium album: the effect of the maternal environment and the N source supplied

Abstract

To study the effect of the maternal environment and N sources in responses to shading in Chenopodium album L., seeds from plants grown at an ambient red/far red (R/FR) ratio (1.07) or a low R/FR ratio (0.39) were germinated in a greenhouse at ambient light. At 34 d after sowing (d.a.s.), they were exposed to either ambient R/FR (0.98) or low R/FR (0.21) progeny light treatments and fertilized with 2.7 mmol/L nitrogen supplied at 1:3 or 3:1 NO3– : NH4+ ratios. Two harvests were performed at 67 and 113 d.a.s. At each harvest, stem elongation traits and biomass of plant organs were recorded. In the first harvest, tissue N% and free NO3–-N concentrations were analyzed. In the first harvest, plants from the low R/FR maternal treatment were heavier and taller than the maternal controls when grown at an ambient R/FR and with a high NO3– supply. At the second harvest this difference persisted in most of the conditions tested. Stem elongation and relative biomass allocation to the stem increased in the low R/FR treated plants, although the effect varied during ontogeny and with the maternal and nutrient treatment considered. The studied factors also affected N acquisition and metabolism. It is concluded that responses to the light spectral quality as well as plant N economy are influenced by the R/FR ratio of the maternal environment and that their expression may be altered by the relative availability of NO3–-N and NH4+-N.Key words: ammonium, Chenopodium album, light spectral quality, maternal effects, nitrate, shade-avoidance responses.