U. Falkengren-grerup et al., Uptake capacity of amino acids by ten grasses and forbs in relation to soil acidity and nitrogen availability, ENVIR EXP B, 44(3), 2000, pp. 207-219
Uptake capacity of organic nitrogen was studied in solution experiments on
eight grasses and two forbs growing in acid soils with relatively high nitr
ogen mineralisation in southern Sweden. Uptake of a mixture of amino acids
(alanine, glutamine, glycine), that varied between 1.6 and 6.3 mu mol g(-1)
dw root h(-1), could not be explained by soil data from the species' field
distributions (pH, total carbon and nitrogen, potential net mineralisation
of ammonium and nitrate). The ratio between organic and inorganic nitrogen
(methylamine) uptake was < 0.05 for the forbs, higher for the grasses with
a maximum of 1.42 for Deschampsia flexuosa. The ratio was negatively corre
lated with measures related to soil acidity (Ellenberg's R-value, soil nitr
ate and total carbon) but not, as hypothesised, with the total amount of mi
neralised nitrogen. The total demand on nitrogen by all components of the e
cosystem would probably have described the extent to which competition amon
g and between plants and microbes induced nitrogen limitation. In a methodo
logical study two grasses were exposed to pH 3.8, 4.5 and 6.0 and to 50, 10
0 and 250 <mu>mol l(-1) of three amino acids. Uptake was also compared betw
een intact plants and excised roots. The treatment response varied consider
ably between the species which stresses the importance of studying intact p
lants at field-relevant pH and concentrations. (C) 2000 Elsevier Science B.
V. All rights reserved.