Absorption of gold by plants

Rooted plants and unrooted cuttings of impatiens (Im• patiens holstii) and garden balsam (I.balsfMnina) did not absorb through roots, or absorb and transport through cut stems, gold sols reduced by glucose or sodium oxalate that contained Au 198 , as shown by leaf autoradiographs.Radioactive gold from a chloride solution was not found in leaves of rooted impatiens and garden bal: sam plants but was found in leaves of unrooted cuttings, even though some of the gold was precipitated as a blue coating of colloidal gold on the cut surfaces and in vascular cells.Leaf auooradiographs showed that Au 198 in solutions of gold cynanide, bromide, iodide, and thiocyanate was absorbed by both rooted plants and unrooted cuttings but that generally more was absorbed by the unrooted cuttings.The concentrations used produced necrosis of the plants.Rooted plants in more dilute Au 198 CN absorbed radioactive gold and transported it to the leaves while the plants produced new root growth and flowers.Radioactive gold in a thiosulfate solution was not absorbed by rooted plants, but large amounts of it were absorbed by unrooted cuttings.Radioactive gold solubilized by an extract from flax plants that contained hydrogen cyanide derived by enzymatic action on a natural glycoside was absorbed in greater amounts by rooted plants than by unrooted cuttings.Atomic absorption analyses of stems and leaves of Impatiens showed that nonradioactive gold (Au 197 ) chloride, cyanide, bromide, iodide, and thiosulfate were readily absorbed by both rooted plants and unrooted cuttings.Of these compounds, gold cynanide was absorbed in the largest amounts and constituted as much as 320 parts per million of the dry weight of the plant.Roots of onion (Allium cepa) bulbs readily precipitated colloidal gold from solutions of gold chloride and gold bromide.Roots of this plant were able to grow in lengrt;h in dilute gold cyanide solutions.The experiments indicated that dilute solutions of gold cyanide were readily absorbed without causing damage to rooted plants.If gold is present in the soil and if cyanogenic plants are rooted in this soil, a mechanism is present for the entrance of gold into the biogeochemical cycling process.