Physiological differences among populations of Anthoxanthum odoratum L. collected from the Park Grass Experiment, Rothamsted. 1. Response to calcium.
Populations of A. odoratum were collected from contrasting plots of the Park Grass Experiment, Rothamsted, grown under identical conditions for 6-18 months, and then grown in sand-culture experiments. Ca concentration in the culture solution affected the dry weight yield of populations from limed plots more than that of populations from unlimed plots. The response of each population to plots more than that of each population to Ca was closely correlated with the soil pH of its source plot (r = 0.90), and with the soil Ca status of its source plot (r = 0.86); the differences evolved within 50 years and over distances of <30 m. The concentration of Ca and P in the shoots of populations from unlimed plots was greater than that in populations from limed plots but the concentration of K, Mg and Na was similar in all populations. Total Ca uptake per plant was 30% greater among populations from unlimed plots than those from limed plots, when 2 mgCa/l was supplied, but was similar in both population types when 54 or 162 mgCa/l was supplied. At given low concentrations of Ca in the shoot, populations from unlimed plots produced relatively more DM than those from limed plots. Differences between Park Grass populations in response to Ca were as great as those between natural populations of A. odoratum or between ecologically contrasting grass species collected from an equivalent range of soils. The differences between populations of A. odoratum in response to Ca and to other soil factors appeared to be large enough to account for the wide edaphic distribution of A. odoratum both on the Park Grass experiment and at large.