Sodium Absorption and Distribution in Forage Grasses of Different Potassium Status

The absorption and distribution of sodium were examined in threegrasses grown in flowing solution culture with different suppliesof potassium. There were marked differences between the speciesin the rate of absorption by their roots, timothy absorbingat a much slower rate than either ryegrass or cocksfoot. Inall species, the rate of Na absorption was greatest when therewas a maintained supply of K and/or when the K contents of theplants were high. Transport of Na from roots to shoots of timothywas restricted; it was less restricted in the other speciesand large proportions of the Na moved from roots to shoots whenK was not supplied to the plants. Sodium transported from theroots accumulated in old leaves and not in the younger leaves.When K was no longer supplied, the growth of ryegrass was maintainedin the plants previously grown with Na plus K; Na supplied insteadof K, however, did not maintain growth. Cocksfoot grown withNa grew less well than when grown without Na when plants wereno longer supplied with K; the growth of timothy was unaffectedby Na. Dactylis glomerata L., Lolium perenne L., Phleum pratense L., cocksfoot, ryegrass, timothy, absorption of ions, distribution of ions, potassium, sodium