Absorption of Gold 

by Plants · 

GEOLOGICAL SURVEY BULLETIN 1314-B ' 
Absorption of Gold 

by Plants 

By HANSFORD T. SHACKLETTE, HUBERT W. LAKIN, ARTHUR E. HUBERT, and 

GARY C. CURTIN 

CONTRIBUTIONS TO GEOCHEMISTRY 

G E 0 L 0 G I C A L S U R V E Y B U L L E T I N 13 14-B 

A report of experiments on the uptake and 

movement ..r A 197 d A 198 • d :.n: o1 u an u tn t

11 erent 

sols and solutions by rooted plants and 

unrooted plant cuttings 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1970 
UNITED STATES DEPARTMENT OF THE INTERIOR 

WALTER J. HICKEL, Secretary 

GEOLOGICAL SURVEY 

William T. Pecora, Director 

For sale by the Superintendent of Documents, U.S. Government Printlni Office 

Washtnaton, D.C. 20402 - Price 30 cents (paper cover) 
CONTENTS 

Page 

Abstract_________________________________________________________ B1 

Introduction______________________________________________________ 2 

Materials and methods____________________________________________ 5 

Gold sols and solutions________________________________________ 5 

Radioactive gold experiments_______________________________ 5 

Colloidal gold_________________________________________ 5 

Gold solutions_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 5 

Nonradioactive gold experiments____________________________ 7 

Plants------------------------------------------------------- 7 

Species used______________________________________________ 7 

Methods of treatment_____________________________________ 8 

Radioactive gold experiments___________________________ 9 

Nonradioactive gold experiments________________________ 10 

Results__________________________________________________________ 11 

Radioactive gold experiments ________________________________ --- 11 

Gross effects on plants------------------------------------- 11 

Autoradiographs------------------------------------------ 15 

Nonradioactive gold experiments________________________________ 18 

Gross effects on plants_____________________________________ 19 

Atomic absorption analyses_________________________________ 19 

SummarY-------------------------------------------------------- 21 

Conclusions------------------------------------------------------ 22 

References cited__________________________________________________ 22 

ILLUSTRATIONS 

Page 

FIGURE L Photograph of mature flowering plants of impatiens (Impatiens 

holstii) and garden balsam (I. balsam ina)_________________ B8 

2. Photograph of onion (Allium cepa) bulbs with roots that 

developed in tap water_________________________________ 9 

3. Autoradiographs of Impatiens leaves from rooted plants and 

unrooted cuttings that were in radioactive gold sols and 

solutions_____________________________________________ 16 

TABLES 

Page 

TABLE 1. Organization and results of experiments in radioactive gold B12 

absorption by plants ________________________ -----------

2. Organization and results of experiments in nonradioactive gold 

absorption by plants___________________________________ 20 

III 

CONTRIBUTIONS TO GEOCHEMISTRY 

ABSORPTION OF GOLD BY PLANTS 

BY HANSFORD T. SHACKLETTE, HuBERT W. LAKIN, 

ARTHUR E. HuBERT, and GARY C. CURTIN 

ABSTRACT 

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 Au198, 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 Au198 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 

Au198CN 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 (Au197 ) 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. 

Bl 
B2 CONTRIBUTIONS TO GEOCHEMISTRY 

INTRODUCTION 

The presence of gold in plants, as determined by chemical analysis, 

was reported more than a century ago (Malte-Brun, 1824, p. 221). 

Careful quantitative experiments performed by Harrison (1908, p. 

209-210) with tree samples from an auriferous region of British Guiana demonstrated that the concentrations of gold in ash of wood and 

bark were small, ranging from 0.06 ppm (parts per million), or 1 grain 

per ton, in bark to 0.6 ppm in wood from the interior of the tree. Later 

investigators reported the gold content of many species of plants from 

various localities throughout the world. Although the amounts given 

in some reports seem too large (as pointed out by Cannon and others, 

1968), the fact that plants can !absorb gold from the soil solution is 

well established. The amounts found in plant ash are usually much 

smaller than 1 ppm. Gold is not known to be essential for plant 

metabolism, and hence it may be classed ns a "ballast" element in 

plants. 

There is no general agreement among investigators as to the forms of 

gold that are absorbed by plants-that is, whether the absorbed gold is 

in colloidal-size particles or in water-soluble compounds. The purpose 

of the experiments described in this report was to determine if plants 

can ·absorb some colloidal gold sols and solutions of gold that may be 

found in the natural environment of plant roots. 

The movement of gold in various inorganic geochemical environments was discussed by Chukhrov (1947), Krauskopf (1951), Goldschmidt (1954), R'ankama and Sahama (1955), Cloke and Kelly 

( 1964), and other workers ·and will not be reviewed here. The fact that 

gold is deposited in plant tissues suggests that it, along with many 

other metals, enters into the biogeochemical cycling process, which 

results in .an enrichment in metals of the upper soil horizons, as pointed 

out by Goldschmidt (1937, p. 670--671). Malyuga (1964, p. 67) 

described the absorption and disposition of metals by plants as follows: 

Depending on the physiological function, the metal enters into the plant tissue 

or is fixed by organ,ic molecules (proteins, vitamins, enzymes). If the plant does 

not use all the elements entering together with the basic nutrients, it frees itself 

of them, discarding them into protective and structural tissues, or, finally, into 

organs and tissues which are being renewed or are dying (leaves, rootlets). 

Under all condi·tions there is a certain accumulation of heavy metals in the 

organic residue of the soil. With the decomposition of the stems, leaves, and dead 

roots of the plant, the heavy metals, together with the most stable organic compounds, remain in the humus layer of the soil. 

Studies by Curtin, Lakin, Neuerburg, ·and Hubert (1968) showed that 

enrichment of gold occurs in mull (humus-rich forest soil) which overlies gold deposits and that analysis of this mull may be a useful method 

of prospecting for gold. 
ABSORPTION OF GOLD BY PLANTS B3 

The physical or chemical state of the gold that moves into plants 

and through the biosphere has been a subject of much speculation but 

little experimentation. Lungwitz ( 1900, p. 501) at first proposed that, 

in nature, gold is dissolved in cyanide, but he later rejected this theory 

because not even traces of cyanide had been reported to be produced by 

the natural decomposition of organic matter. He next considered gold 

chloride as a compound that might enter vegetation but questioned the 

effectiveness of this compound because it was not expected to "withstand the reducing action that untold numbers of cell membranes and 

cell contents must exert." He reported that tree roots had been examined for gold which might have precipitated on them but that no gold 

had been found, and he emphasized the impossibility of the occurrence of such a precipitation. 

The relative concentrations of gold in seeds, seed pods, leaves, upper 

twigs, stems, and roots, as determined by activation analysis, were 

studied by Khotamov, Lobanov, and Kist (1966). They found the 

maximum content to be in leaves and suggested that only the leaves 

need be analyzed in biogeochemical prospecting for gold. 

Chukhrov (1947) concluded that the dissolution of gold as bromide 

and iodide occurred in the oxidation zone of sulfide-type deposits, but 

he did not discuss the availability of these compounds to plants. 

Listova, Vainshtein, and Ryabinina (1966) reported experiments 

on the dissolution of gold in solutions formed during oxidation of 

natural sulfides of lead, zinc, and iron. The presence of carbonates 

shifted the process of sulfide oxidation toward increased concentrations 

of intermediate products of sulfide oxidation. The calcium thiosulfate 

and calcium polythionate that formed during the reaction of carbonates with the products of sulfide oxidation were found to be solvents 

of gold, and, being easily soluble compounds, they can exist in and 

migrate with surface waters for a prolonged time. These observations 

suggest that gold thiosulfate may be absorbed by plants in a natural 

environment. 

In their study of gold in rocks, plants, and waters of the Darasun 

gold deposit (U"SSR), Aferov, Zvyagin, Roslyakova, Roslyakov, Sha·· 

bynin, and Epov (1968) concluded that the ion-complex form is the 

most probable form of gold migration in contemporary waters and 

inferred that the gold found in plants on this deposit had been a.bsorbed in this form. 

Ong and Swanson ( 1969) reported that in the interactions of gold 

with different types of natural organic acids, the gold is not oxidized 

and complexed by the organic molecules but that organic concentra-
B4 CONTRIBUTIONS TO GEOCHEMISTRY 

tions in the range of 3-30 ppm can reduce gold chloride solutions to 

negatively charged colloids of metallic gold. They stated (p •. 395): 

For the 30-ppm organic acid solutions, the reduction process is accomplished 

by the formation of a protective coating of hydrophilic organic molecules 

around the hydrophobic gold sol making the gold very stable for at le:;tst 8 · 

months and not easily coagulated by cations. The gold sols so formed ar~ less 

than 10 mp. [millimicrons] in size. This protective layer is also formed when 

colloidal gold is mixed with organic acids. For the 3-ppm organic acid, the 

organic matter concentration is too low to form the protective coating and the 

colloidal gold precipitates. 

Gold sols of 10 mp. size theoretically could enter into the vascular system of a plant, if the stem were cut so that the conducting tissues were 

directly exposed to the sols, but most likely could not pass through 

the membranes of root cells. 

Glycosides which yield hydrocyanic acid upon hydrolysis by enzymatic action are found in many species of plants. Conn (1969, p. 519) 

stated, "Approximately 1,000 plant species representing 90 families 

and at least 250 genera have been reported to be cyanogenic. Several 

dozen species have been studied in greater detail, in some instances 

because of their economic significance, and 11 cyanogenic glycosides 

have been identified." Hydrocyanic acid and thiocyanates have been 

isolated from plants which had caused poisoning of livestock (Kingsbury, 1964); both of these compounds are formed from glycosides and 

both are solvents of gold. 

Not only leafy plants but also certain fungi produce cyanide compounds. The mycelium of Marismius oreades (Bolt. ex Fr.) Fr., a 

mushroom of the order Agaricales, was reported by Filer (1965) to 

produce hydrogen cyanide, and the presence of this compound was 

linked to the occurrence of patches of dead turf in lawns. Other species 

of fungi also have been determined to be cyanogenic. 

In a study of the resistance of cultivated flax (Linum usitatissi1num L.) to the fungus Fusarium lini., Reynolds ( 1931) reported that 

varietal resistance depended on the amount of the glucoside linamarin 

in the plant tissue. Timonin (1941, p. 406--407) demonstrated that the 

linamarin in flax is hydrolyzed to form hydrogen cyanide and that in 

laboratorye:Xperiments 25-37 mg (milligrams) of this compound was 

excreted or diffused from the root system of a single flax plant into 

the surrounding medium. He stated further (1941, p. 407) that 

"it can be assumed that the same toxic matter [hydrogen CY'anide] 

is secreted by the resistant variety under natural (field) conditions." 

Rovira (1969, p. 44) reported that potassium cyanide may ftffect 

permeability of root cells, thereby causing an increase in root exudation of radioactive chloride, a substance generally accepted to move 

passively (without requiring metabolic action) out of roots. It is not 

known if hydrogen cyanide causes a similar effect on the permeability 
ABSORPTION OF GOLD BY PLANTS B5 

of root cells. According to Rovira (1969, p. 47), plant substances found 

in soils may have been produced by the leaves, leached from the leaves 

and deposited in soil, produced from decomposing root residues, and 

exuded from healthy intact roots. 

Because of the widespread distribution of higher plants and other 

organisms that contain cyanogenic substances, the solubilization of 

ntttive gold by hydrogen cyanide and the absorption of cyanide compounds of gold by various plant species ,are likely to occur in natural 

environments. 

MATERIALS AND METHODS 

GOLD SOLS AND SOLUTIONS 

RADIOACTIVE GOLD EXPERIMENTS 

In these experiments, we used sols and solutions of gold that, at 

lower concentrations, could occur in soils on which plants grow over 

gold deposits. A list of these gold-bearing preparations and a description of the method used in the preparation of each, follow. 

COLLOIDAL GOLD 

1. HAuC14 reduced U'ith glucose/ gelatin used as a protective colloid 

Heat to incipient boiling 100 ml {milliliters) of a 5-percent solution of gelatin (Eastman 1099, purified calfskin) and 5-percent 

D-glucose anhyd. Then add slowly 2 ml of 0.6-percent HAuC14 

solution and 4 ml of HAu198Cl4 (0.8 millicurie Au198 ) and continue heating-but not to boil-until a red sol is produced. Add 

demineralized water to make final volume 500 ml and adjust pH 

to 6.2 with 0.2 N potassium hydroxide. A gold sol prepared in 

this manner but without Au198 passed through a 0.05-micron filter. 

The preparation is a modification of the procedure Qf Henry, 

Herczeg, and Fisher (1957). 

2. HAuC14 reduced 1lYith sodium oxalate 

To 500 ml of demineralized water add 2 ml of 0.6-percent HAuC14 

solution, 4 ml of HAu198Cl4, and 6 ml of L-percent sodium oxalate 

solution. Heat to boiling and continue gentle boiling until a 

bluish-purple sol is formed. Cool and adjust pH to 6.2 with 0.2 

N potassium hydroxide. A gold sol prepared in this manner but 

without Au198 passed through a 0.45-micron filter, but none passed 

through a 0.05-micron filter. 

GOLD SOLUTIONS 

1. Gold chloride solution 

To 500 ml of demineralized water add 11nl of 0.6-percent HAuC14 

solution and 4 ml of HAu198Cl4 and stir to mix thoroughly. The 

pH of the final solution was 6."2. 

373-711 0-70-2 
B6 CONTRIBUTIONS TO GEOCHEMISTRY 

2. Gold cyanide solution 

· Place a sheet of leaf gold (15 mg Au) in 50 ml of 0.2-percent 

sodium cyanide solution and allow to stand overnight to effect 

solution of the gold. Evaporate to dryness 4 ml of HAu198Cl4 and 

heat in a flame to reduce the gold ion to the metal, then dissolve 

in 10 ml of 0.2-percent sodium cyanide. Combine the two solutions and dilute to 500 ml with water. Adjust the pH to 6.5 with 

dilute sulfuric acid. 

3. Gold brom-ide so7Jution 

Place a sheet of leaf gold (15 mg Au) in a 150-ml beaker~ add 

4 ml of HAu198Cl.1, and evaporate the solution to dryness and 

heat in a flame to reduce the gold chloride to the metal. Add 10 

ml of concentrated hydrobromic acid which contains 0.5-percent 

bromine and dilute to 500 ml with water. Adjust pH to 6.2 with 

0.2 N potassium hydroxide. 

4. Gold iod·ide solution 

Place a 15-mg sheet of leaf gold in a 150-ml beaker, add 4 ml of 

HAu198Cl4 , and evaporate the solution to dryness. Heat in a flame 

to reduce the gold chloride to the metal. Add 20 ml concentrated 

hydroiodic acid and a few crystals of iodine. After solution of the 

gold, warm on the hotplate to expel the excess iodine. Dilute to 

500 ml with water and adjust to pH 6.0 with 0.2 N potassium 

hydroxide. 

5. Gold thiocyanate solution 

Place a 15-mg sheet of leaf gold in 500 ml of 0.2-percent solution 

of potassium thiocyanate and allow to stand, but occasionally 

shake, for 3 days. Filter and add 4 ml HAu198Cl4 solution to the 

filtrate and adjust the pH to 6.2 with dilute sulfuric acid. The 

gold content of the solution was found to be 0.08 ppm. 

6. Gold thiosulfate solution 

Place a 15-mg sheet of leaf gold in 500 ml of 0.2-percent sodium 

thiosulfate and allow to stand, but occasionally shake, for 3 days. 

Filter and add 4 ml HAu198Cl4 solution to the filtrate and adjust 

the pH to 6.2 with dilute sulfuric acid. The gold content of the 

solution was found to be '2.6 ppm. 

7. Gold cyanide solution via flaw 

Prepare a slurry of wild flax (Li1'111111n lewisii Pursh), using the 

above-ground parts at the flowering stage, in a blender and dilute 

to 800 ml with water. Stir four leaves of gold (60 mg Au) into the 

slurry and allow to stand for 3 days. Centrifuge and decant 

slightly turbid supernatant solution free of particulate gold. 
ABSORPTION OF GOLD BY PLANTS B7 

Evaporate to dryness 4 ml HAu198Cl4 solution and heat in a 

flame to reduce the gold to the metal. Dissolve the gold in 20 ml of 

0.2-percent sodium cyanide and dilute to 500 ml with the flax 

extract prepared previously. Adjust the pH to 5.9 with dilute sulfuric acid. The gold content of the final solution was found to be 

0.5ppm. 

NONRADIOACTIVE GOLD EXPERIMENTS 

In the experiments on the absorption of nonradioactive gold (Au197 ) 

by plants, only gold solutions were used, and they were prepared by the 

methods listed above, except that radioactive gold (Au198 ) was not 

added to the solutions. The organization of these experiments, and the 

solutions that were used, are given in table 2. 

NoTE.-All pH values of gold sols and solutions are approximate, 

obtained by narrow range pH ( 5.0-8.0) paper with visible differences in 0.4 pH values. 

PLANTS 

The experiments on gold absorption by plants were designed to detect gold, if present in the plants, by changes in color of tissues, by 

autoradiographs of leaves, and by atomic absorption analysis of the 

stems and leaves. The gross effects of the gold sols and solutions on the 

plants also were noted. 

SPECIES USED 

We selected cultivars of impatiens (hnpatiens holstii Engler & 

W arb.) and garden balsam ( /. balsamina L.), shown in figure 1, of 

the family Balsaminaceae (Bailey, 1937, p. 1641-1644) for tests of the 

movement of gold through roots and stems and into leaves. These ornamental plants are desirable subjects for these experiments because they 

( 1) readily form roots and root hairs if stem cuttings are placed in 

tap water, (2) transpire freely and have a rapid rate of water conduction through the stems, (3) have stems that are translucent, and therefore colored solutions moving through vascular tissues of the stem can 

be easily observed, ( 4) grow well in the subdued light that commonly is 

provided by plant growth chambers, and ( 5) are insensitive to photoperiod, and therefore are vegetative and reproductive at any time of 

the year. 

We chose onion (Allium cepa L.) bulbs (family Liliaceae) for 

studying the effects of roots on gold solutions and sols because these 

bulbs form abundant roots when partly submerged in water (fig. 2), 

the roots are large (but with root hairs only near the tips) and white, 
B8 CONTRIBUTIONS TO GEOCHEMISTRY 

FIGURE 1.-Mature flowering plants of impatiens (Impatiens holstii), on the 

left, and garden balsam {I. balsamina), on the right. 

and marker dyes are readily absorbed by the roots; hence, growth in 

length can be observed and measured. The roots of both species of 

Impatiens, in contrast, are slender and somewhat fragile and tend to 

develop pigmentation. 

METHODS OF TREATMENT 

The Impatiens cuttings were rooted in the same test tubes in which 

they were to remain during the experiments in order to prevent root 

damage in transferring them to other containers. Many roots formed 

on the stems during the 2-week period that they remained in a shaded 

greenhouse, and calius tissue grew over the exposed vascular tissue of 

the cut ends of the stems. The onion bulbs were rooted by submerging 

t~e lower part of the bulb in tap water in disposable beakers; they 

were kept in a dark growth chamber at a temperature of 14°0. The 

cool temperature inhibited rotting of the bulbs, and many roots were 

fQrmed in the 2-week period. 
ABSORPTION OF GOLD BY PLANTS B9 

FIGURE 2.-0nion (Allium cepa) bulbs with roots that developed in tap water. 

The roots of the bulb on the left remained in tap water and are a normal white 

color, but the roots of the bulb on the right were placed in gold chloride solution and are colored dark blue by colloid>al gold which was precipitated out of 

the solution on contact with the roots and deposited on the root epidermis. 

The gold chloride solution in which onion roots were placed turned blue, 

whereas the solution remained colorless if it did not contain the roots. 

RADIOACTIVE GOLD EXPERIMENTS 

At the beginning of the tests for radioactive gold absorption, the 

tap water in the test tubes of rooted cuttings was poured off, and the 

gold sols ·and solutions (listed in table 1) were added. Care was taken 

to prevent contamination of the lea.£ surfaces with the solutions. 
BlO CONTRIBUTIONS TO GEOCHEMISTRY 

U nrooted cuttings of Impatiens were excised from healthy potted 

plants (fig. 1) and were immediately placed in the gold solutions. Tap 

water in the beakers that contained the rooted onion bulbs (fig. 2) was 

poured off and replaced with the gold solutions. All test plants were 

then placed in a growth chamber in which 12 hours of fluorescent 

illumination (approximately 1,000 foot-candles intensity) and a temperature of 24°C alternated with 12 hours of darkness and a temperature of 14°C. A fan in the growth chamber introduced fresh air and 

promoted rapid transpiration. 

After 24 hours, the Impatiens plants were removed from the growth 

chamber, their physical condition was noted (table 1), and one leaf 

of each plant was excised and placed in a black paper cassette £or 

making the autoradiographs. The plants were then returned to the 

growth chamber. Industrial G X-ray film was used to record the disintegrations o£ Au198 in the leaves. A sheet of black paper and a sheet 

of acetate film which acted as a moisture barrier separated the leaves 

from the sensitive strips of film. The cassettes with their enclosed 

leaves were placed side by side in a light-tight box and allowed to 

remain at room temperature for a period o£ 90 hours. The leaves were 

removed from the cassettes at the end of this period, and the exposed 

films were processed in commercial X-ray developer for 5 minutes at 

a temperature o£ 20°C, transferred to a fixing solution for 5 minutes, 

and then washed and dried. 

The onion roots were observed after they had been in the gold 

solutions 24 hours and again, with the Impatiens, after 48 hours; their 

reactions are noted in table 1. At the end of this period, all plants 

were discarded. 

NONRADIOACTIVE GOLD EXPERIMENTS 

The same kinds o£ Impatiens plants as those used in the radioactive 

gold experiments were used for nonradioactive gold experiments; they 

were also prepared in the same manner and were kept under similar 

environments. The roots on the cuttings, however, were not as well 

developed as those on cuttings used in the Au198 experiments. 

Tap water in the test tubes that contained the rooted plants and 

unrooted cuttings was poured off and replaced with the solutions of 

nonradioactive gold (Au197 ); the plants were then pla.ced in the 

growth chamber where they remained 24 hours. At the end o£ this 

period, the gross effects of the solutions on the plants were noted, and 

these observations were repeated after 48 hours. The parts of the 

plants that extended above the tops of the test tubes were then excised 

(taking care that the gold solutions did not come in contact with these 

parts) , dried 24 hours in an oven with circulating 'varm air, burned 

to ash, and the ashes analyzed for gold by atomic absorption methods. 
ABSORPTION OF GOLD BY PLANTS Bll 

Because of the very small amount of ash produced by burning a 

sample, the gold content of the plants was computed as parts per 

million of the dry plant. In order to provide a value tha.t could be 

used to convert parts per million in the dry plant to parts per million 

in ash, composite samples consisting of 12 cuttings of each species of 

Impatiens were dried and burned to ash. The percentage of ash in the 

dry plants is given in table2. 

RESULTS 

RADIOACTIVE GOLD EXPERIMENTS 

GROSS EFFECTS ON PLANTS 

The organization of the experiments and the visible effects of the 

radioactive gold sols and solutions on the plants are given in table 1. 

Wilting of leaves and stems usually was the first noticeable effect 

of the sols and solutions on Impatiens. Leaves may be prevented from 

obtaining sufiicient water to maintain their normal turgor pressure, 

and therefore wilt, by a failure of the water-absorbing and transporting systems of roots and stems. Leaves may wilt also because of damage 

to or destruction of the osmotic properties of leaf cell membranes. 

If leaves wilt but otherwise appear normal, failure of the absorbing 

and transporting system only is indicated. This failure may be caused 

by mechanical blocking of the absorbing surfaces or by necrosis of the 

absorbing and transporting cells. If, however, symptoms of leaf necrosis appear, wilting may be the result of damage to osmotic membranes 

of the leaf, either with or without failure of the absorbing system. 

The sols and solutions used in these experiments may either block 

absorbing surfaces or exposed vascular elements by depositing colloidal 

gold or other materials or may cause cell necrosis by means of ionizing 

radiation or by liberation of phytotoxins. Radioactive gold (Au198 ) 

disintegrates into a nonradioactive isotope of mercury (Hg198 ), and 

metallic mercury or compounds of mercury generally are toxic to plant 

cells. Other phytotoxins in the solutions also m·ay have caused necrosis 

of the Impatiens; chlorine, bromine, iodine, and cyanide generally 

are lethal to plant cells, except when in very low concentrations. 

Rooted Impatiens in the two gold sols remained turgid or wilted 

slightly at first but regained turgor pressure in 48 hours. U nrooted 

cuttings in glucose-gelatin sols were severely wilted, whereas those in 

sodium oxalate sols remained turgid or only wilted moderately. 

The reason for this difference in plant reaction to the two sols is not 

known. The results suggest, however, that some property (perhaps 

the gelatin) of the glucose-gelatin sol caused a slight to extensive 

blocking of the exposed vascular cells of the unrooted cuttings which 
TABLE I.- Organization and results of experiments in radioactive gold absorption by plants 

[Number in parentheses in boxhead is radioactivity, in counts per minute, at beginning of experiments. To determine counts per minute, the activity of 10-ml aliquots of the 

sols and solutions was measured by a scintillation counter using a well-type 1.5-in. thallium-activated sodium iodide crystal detector] 

Experimental plants 

Impatiens (Impatiens holstii): 

Visible effects on plants in radioactive gold (Aulis) sols and solutions as observed after (a) 24 hr and (b) 48 hr 

Glucose-gelatin sol 

(2,930) 

Sodium oxalate sol 

(3,120) 

Gold chloride solution 

(2,310) 

Gold cyanide solution 

(1,800) . Gold bromide solution 

(3,500) 

Rooted _______________ ______ _____ a. Leaves slightly wilted __ a. Leaves turgid __ __ _____ _ a. Leaves turgid ________ __ a. Leaves moderately a. Leaves turgid. 

b. Leaves turgid _____ ___ __ b. ____ do_ b. ____ do _ wilted. 

b. Leaves slightly wilted __ b. Leaves abscissing; stem flaccid. 

Not rooted ____ __ _________ ___ ___ _ a. Leaves severely wilted_ a. Leaves turgid _____ _____ a. Leaves turgid __ ______ __ a. Leaves severely wilted_ a. Leaves moderately 

Garden balsam (Impatiens bal- samina): 

b. -- --UU __ _ ___ _ b. ___ _ do _ b. Leaves turgid; blue precipitate on cut surface of stem and 

in stele. 

wilted. 

b. Total necrosis __ ______ __ b. Leaves severely wilted . 

Rooted _______________ _____ ______ a. Lower leaves slightly a. Leaves turgid _____ _____ a. Leaves turgid _____ ___ __ a. Leaves severely wilted, a. Leaves severely wilted. 

wilted. stem flaccid. 

b. All leaves turgid _____ __ b. ___ _ do __ ------- _____ b. ____ do ___ ___________ ____ b. Total necrosis ______ ____ b. Total necrosis. 

Not rooted ______ ___ __ __ _________ a. Leaves severely wilted_ a. Leaves moderately a. Leaves turgid __ __ ______ a. Leaves severely wilted_ a. Leaves turgid. 

b. ____ do_ 

Onion (Allium cepa), rooted _______ __ a. No effects. Sol re- mained pink. 

b. ____ do_ 

wilted. b. ____ do_ 

a. No effects. Sol re- mained pale pink. 

b. ____ do_ 

b. Leaves moderately wilted; blue pre- cipitate in stele. a. Root epidermis sloughing and 

covered with darkblue precipitate. b. Clear solution turned 

light blue. 

b. Total necrosis ________ __ b. Do. 

a. No effects. Solution 

remained clear. 

b . ____ do_ 

a. Root epidermis dark 

blue, no sloughing.; 

b. Do. 

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Gold iodide solution (2,930) Gold thiocyanate solution (6,700) Gold thiosulfate solution (4,000) Flax plant extract I (3, 730) 

Impatiens (Impatiens holstii): Rooted _____________ _____________ a. Leaves turgid __ ----- ------ ____ a. Leaves turgid ___ ___ ___ _____ ___ a. Leaves turgid ____ __ _________ __ a. Leaf margins necrotic. 

b. Leaves abscissing; stem b. ___ _ do __ --- ------------------- b. ____ do __ ---------------------- b. Leaves severely wilted. flaccid. 

Not rooted _______________ _______ a. Leaves severely wilted ______ __ a. Leaves moderately wilted _____ a. Leaves turgid __ -- --- -------- __ a. Leaves severely wilted. 

Garden balsam (Impatiens bal- samina): 

b. Leaves severely wilted and b. All leaves abscissing __ ______ ___ b. ____ do __ --------------- ------- b. Do. abscissing. 

Rooted ____________________ ______ a. Stem and leaves turgid; a. Leaves turgid __ ___ __________ __ a. Leaves turgid ____ _______ ____ __ a. Leaves very slightly wilted. 

leaves abscissing. b. ____ do _________________________ b. ____ do __ ---------------------- b. ____ do ____ ______ ·------------- b. Do. 

Not rooted ______________ ________ a. Leaves very slightly wilted ___ a. Leaf margins necrotic _________ a. Leaf margins necrotic _________ a. Leaves severely wilted. 

b. Leaves severely wilted ____ ____ b. Entire leaf necrotic ____________ b. ____ do __ ----- ----------------- b. Do. Onion (Allium cepa), rooted _________ a. Root tips brown. Solution a. No effects. Solution remained a. No effects. Solution remained a. No effects. Solution remained remained clear. clear. clear. brownish yellow. b. ____ do ___ _____________________ b. ___ _ do __________ ______________ b. ____ do ___ _________ _________ ___ b. Do. 

I Gold dissolved in extract prepared from above-ground parts of wild flax (Linum lewisii) that was in flower. 

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B14 CONTRIBUTIONS TO GEOCHEMISTRY 

impeded the uptake of water but that rooted plants were able to absorb 

water normally through the root membranes without appreciable interference from the sols. All p1ants and cuttings remained alive and 

seemed to sustain no significant cell da.mage in stems and leaves; this 

fact suggests that radioactive gold was not translocated through the 

stems and into the leaves, as was demonstrated by the leaf autoradiographs. The onion roots showed no effects of being submerged in 

the sols. 

Rooted plants in the gold chloride solution remained turgid, as did 

the unrooted cutting of impatiens. The garden balsam cutting was 

moderately wilted. A blue precipitate of colloidal gold was deposited 

on the cut surfaces and in the conducting tissues of the unrooted cut,. 

tings. The precipitated gold colloid apparently could not pass through 

the membranes of the root cells, as is indicated by the autoradiographs, 

but it did not prevent the movement of water into the roots. The onion 

roots precipitated the gold; the sloughing epidermis was dark blue, 

and the solution turned light blue (fig. 2). 

All Impatiens in the gold cyanide solution were moderately to severely wilted within 24 hours, and all but one were dead within 48 

hours; necrosis was evident in roots, stems, and leaves. There was no 

precipitation of gold on either the Impatiens roots or stems or on the 

onion roots. 

The gold bromide solution caused severe wilting of all impatiens 

within 48 hours, and all plants were moribund or dead soon thereafter. 

The onion roots precipitated gold from the solution, but the Impatiens 

roots did not. 

The gold iodide solution caused all leaves to wilt and to fall from 

the stems. Neither Impatiens nor onion roots caused precipitation of 

gold. 

Rooted Impatiens in the gold thiocyanate solution remained turgid, 

whereas the leaves of unrooted cuttings wilted and either fell from the 

stems or became necrotic. Neither Impatiens roots nor onion roots 

caused precipitation of the gold. 

All Impatiens in the gold thiosulfate solution remained turgid; the 

leaf margins, however, of the unrooted garden balsam became necrotic. 

None of the plants precipitated gold from the solution. 

The solution of gold in flax extract severely damaged all Impatiens 

except the rooted garden balsam. No gold was precipitated from the 

solution. 

Because of our special interest in the transport of gold that is dissolved by cyanide, we performed experiments in addition to those 

reported in table 1 and figure 3. A dilute solution with respect to Au198 

was prepared by evaporating a solution that contained 15 mg gold 

chloride and 1 ml of HAu198Cl4 solution to dryness and dissolving in 

20 ml of 0.2-percent potassium cyanide, diluting to 400 ml, and adjust-
ABSORPTION OF GOLD BY PLANTS B15 

ing the pH to 11.0. Rooted pla.nts and unrooted cuttings of impatiens 

(Impatiens holstii) we,re used for the experiments. The roots of one 

plant were stained red with food color before the experiment started 

and then were washed to remove exce•SS color and placed in the gold 

cyanide solution. Both the rooted plant and the unrooted cutting remained turgid while in the solution for 48 hours, and showed no indication of necrosis. During this period, the rooted pla.nt produced about 

5 mm (millimeters) of white new growth on each root that contrasted 

with the red-stained older part of the root, and a flower opened from a 

bud on the stem. A leaf from the rooted plant produced an image 

when exposed to sensitive film for 24 hours, whereas a. leaf from the 

unrooted cutting did not. These plants were kept in the solution several 

days longer; both remained healthy, and the unrooted cutting began 

to form roots just as if it were in tap water. Rooted onion bulbs that 

had their roots.stained red were placed in this solution of gold cyanide. 

They remained healthy and produced 5-7 mm of new root growth in 

48 hours. 

We performed ·another experiment on rooted plants and unrooted 

cuttings of Impatiens and on rooted onion bulbs that were placed in 

the gold cyanide solutions which were prepared as described in the 

first experiments (solution 2 under the heading "Gold solutions')) but 

which had pH values of 6.2, 8.2, and 11.0 and a greater concentration 

of Au198 • Rooted plants of impatiens and garden balsam in the solutions of pH 6.2 and 8.2 were slightly to severely wilted after 24 hours. 

The leaves and stems of all plants but the rooted impatiens were 

severely wilted and necrotic after 48 hours. The leaves of rooted plants 

in the solution that had a pH of 11.0 remained turgid for 24 hours but 

were wilted and necrotic after 48 hours, whereas leaves of unrooted 

cuttings were severely wilted and necrotic. a few hours after being 

placed in the solution. Autoradiographs showed that a large amount 

of Au198 had been deposited in the leaves of all the plants. These solutions caused no appreciable change in the onion roots, and no gold was 

precipitated from the solutions. 

AUTORADIOGRAPHS 

The relative amounts of radioactive gold in leaves of the experimental plants are indicated by the darkness of the imag~up to solid 

black-that is produced on the film. It should be mentioned that the 

sols and solutions contained many times more nonradioactive gold than 

Au198, .and that if both kinds of gold were absorbed in proportion to 

their abundance in the solutions, the autoradiographs indicate only a 

very small part of the total amount of gold in the leaves. Autoradiographs of leaves from rooted plants and unrooted cuttings of impatiens 

and garden balsam are given in figure 3. A series of controls, consisting 
B16 CONTRIBUTIONS TO GEOCHEMISTRY 

Au198 sols and solutions 

Experimental plants 

Impatiens (Impatiens holstii). 

Rooted 

Impatiens (Impatiens holstii). 

Not rooted 

Garden balsam (Impatiens balsamina). 

Rooted 

Garden balsam (Impatiens balsamina). 

Not rooted 

FIGURE 3.-Autoradiographs of Impatiens leaves from rooted plants 
ABSORPTION OF GOLD BY PLANTS B17 

Au198 sols and solutions 

and unrooted cuttings that were in radioactive g·old sols and solutions. 
B18 CONTRIBUTIONS TO GEOCHEMISTRY 

of rooted plants and unrooted cuttings in tap water, was kept under 

the same environment as that of the experimental plants. Autoradiographs of leaves of the controls were negative and are not shown in 

figure 3. 

Radioactive gold of colloidal size in the two sols was not transported 

to the leaves of either rooted plants or unrooted cuttings. A very dim 

leaf image was formed by a leaf from an unrooted garden balsam that 

was in the glucose-gelatin sol; probably the sol contained traces of 

Au198 in solution which produced the image. 

The rooted plants in gold chloride solution transported little or no 

Au 198 to the leaves, whereas the unrooted cuttings transported large 

amounts, in spite of their having precipitated colloidal gold on the 

cut surfaces and within the vascular system of the stems. These results 

suggest that gold chloride is reduced to colloidal gold on contact with 

the plant cells and that the colloidal gold cannot pass through the root 

membranes but can enter the cut vascular tissue and be transported to 

the leaves. If this supposition is correct, the reason is not apparent why 

colloidal gold in the two sols cannot likewise enter the conducting tissues of the cut stems. 

Radioactive gold in gold cyanide, bromide, iodide, and thiocyanate 

solutions was absorbed by both rooted plants and unrooted cuttings, 

but in all experiments (except the autoradiograph of the plant in a 

gold bromide solution) more was ·absorbed by the unrooted cuttings. 

This fact indicates that the compounds damaged the absorptive 

mechanisms of the roots; normally, a rooted plant will absorb more 

water and solutes than will an unrooted cutting of comparable size 

because of the greater surface for absorption that the roots afford. 

Very little or no radioactive gold in the thiosulfate solution was 

absorbed by the rooted plants, but large amounts were taken up by the 

unrooted cuttings. Apparently, membranes of the root cells will not 

permit this compound to pass through them. 

The radioactive gold that was dissolved in flax extract was absorbed 

by both rooted plants and unrooted cuttings, but more was absorbed by 

the rooted plants. This difference in absorption is the normal condition for plants. The compound in the flax plant extract that dissolved 

the gold is hydrogen cyanide that was formed by the action of plant 

enzymes on a glycoside that is present in flax. 

NONRADIOACTIVE GOLD EXPERIMENTS 

The experiments with impatiens and garden balsam, as reported in 

table 1, were repeated substituting nonradioactive gold (Au 197 ) for 

the radioactive gold (Au 198 ) in the solutions (gold in flax extract 

being omitted) in order to determine if ionizing radiation or the toxic 
ABSORPTION OF GOLD BY PLANTS Bl9 

nature of the compounds caused the damage to plants that is reported 

in table 1. In addition, we wished to substantiate the uptake of gold 

by plants as shown by autoradiographs by atomic absorption analysis 

of the plant stems and leaves for gold; nonradioactive gold solutions 

were used for analysis experiments to avoid radioactive contamination 

of the analytical apparatus. 

GROSS EFFECTS ON PLANTS 

The organiz·ation of the experiments and the visible effects of Au 197 

solutions on the Impatiens plants are given in table 2. 

The rooted plants and unrooted cuttings were observed 24 hours 

and 48 hours after they were placed in the solutions. Of the plants 

and solutions that can be compared in tables 1 and 2, visible effects on 

only unrooted impatiens in the gold chloride solution, on rooted garden 

balsam i~ the gold bromide solution, and on unrooted garden balsam 

in the gold iodide and gold thiocyanate solutions differed significantly 

in the two experiments. The reasons for these differences are not apparent. Similar visible effects on the plants used in the two experiments 

indicate that the toxic nature of the solutions alone can cause the wilting and necrosis that occurred-ionizing radiation is not necessary 

to produce these effects. 

ATOMIC ABSORPTION ANALYSES 

The concentration of gold in the dried plants is given in table 2. 

These values can be converted to approximate gold content in ash of 

the plants by considering dry impatiens to yield 8 percent ash and dry 

garden balsam to yield 10 percent ash when burned. 

Although the amoun~s of radioactive gold, as indicated by autoradiographs, and of nonradioactive gold, as determined by atomic 

absorption analysis, do not always correspond for all plants and all 

solutions used in the experiments, gold cyanide is the compound that 

usually was absorbed in the largest amounts in both experiments. The 

pH of the gold cyanide solution appears to affect the amount of gold 

that is absorbed by the plants-small amounts generally are absorbed 

at pH 7.7, and n1uch greater amounts a.re absorbed at pH 11 and 6.5. 

Nonradioactive gold chloride was absorbed in small amounts by all 

plants, whereas radioactive gold was absorbed only in unrooted 

cuttings. 

Gold bromide and gold iodide were absorbed in small to moderate 

amounts in all plants used in both experiments. 

Only very small amounts of nonradioactive gold thiocyanate were 

absorbed by the plants, whereas much larger amounts of the radioactive 

compound were indicated by the autoradiographs. 
TABLE 2.-0rganization and results of experiments in nonradioactive gold absorption by plants 

[Dry impatiens yielded 8 percent ash, dry garden balsam 10 percent ash, when burned. ____ ,no data available. Concentrations of gold in solutions, in milligrams per liter. Gold 

Experimental plants 

Impatiens (Impatiens holstii): 

determined by the method of Thompson, Nakagawa, and VanSickle (1968)] 

Visible effects on plants in nonradioactive gold (Aut97) solutions as observed after (a) 24 hr and (b) 48 hr, and the parts per million (ppm) gold 

in dry plants after they had been in solutions 48 hrs. 

Gold cyanide (29 mgfl) Gold chloride (pH 6.2; 5.7 mgfl) pH 11 pH 7.7 pH 6.5 

Rooted ______________________ a. Leaves slightly wilted ___ _____ __ a. Leaves severely wilted, a. Leaves very slightly wilted ____ a. Leaves turgid. 

necrotic. b. Total necrosis ____________ ______ b. ____ do __________________________ b. Leaves turgid, stem necrotic ____ b. Do. 

160 ppm Au _______________________ 1.7 ppm Au _______________________ 180 ppm Au _______________________ 1.0 ppm Au. 

Not rooted ________ _____ _____ a. Leaves moderately wilted ______ a. Leaves severely wilted ___ ______ a. Leaves severely wilted _________ a. Leaves severely wilted. 

Garden balsam (Impatiens 

balsam ina): 

b. Leaves severely wilted, b. ____ do _____________ ____________ b. Leaves severely wilted, b. Leaves severely wilted, 

necrotic. necrotic. necrotic. 320 ppm Au _____________________ __ 4.2 ppm Au ___ ____ ____________ ____ 130 ppm Au _______________________ 7 ppm Au. 

Rooted __________________________________________ ------------- ___________________________ _______ ____ _ a. Total necrosis __________________ a. Leaves turgid. b. ____ do ____________ ______________ b. Do. 

78 ppm Au ________________________ 7.5 ppm Au. 

Not rooted __________________ a. Severe necrosis _________________ a. Leaves moderately wilted ______ a. Leaves severely wilted; stem a. Leaves moderately wilted. 

Impatiens (Impatiens holstii): 

flaccid. 

b. Total necrosis; plant brown ____ b. Plant necrotic, but green _______ b. Total necrosis ________________ b. Leaves slightly wilted. 

32 ppm Au ________________________ 32 ppm Au __________ _________ __ ___ 260 ppm Au _______________________ 7.5 ppm Au. 

Gold bromide 

(pH 6.2; 29 mg/l) 

Gold iodide 

(pH 6.0; 29 mg/l) 

Gold thiocyanate 

(pH 6.2; 0.1 mgfl) 

Gold thiosulfate 

(pH 6.2; 2.2 mg/l) 

Rooted ______________________ a. Leaves turgid __________________ a. Leaves slightly wilted __________ a. Leaves very turgid _____________ a. Leaves turgid. 

b. Leaves very slightly wilted; b. Leaves severely wilted, leaf b. ____ do ___________ _______ ___ ____ b. Leaves very turgid. 

blue deposit on stems and abscission. roots. 28 ppm Au ___ ______________ _____ __ 64 ppm Au ______________ __ ____ ____ <I ppm Au ____ ___ ____ _________ ___ 1.4 ppm Au. 

Not rooted __________________ a. Leaves severely wilted _______ __ a. Leaves severely wilted and a. Leaves severely wilted _________ a. Leaves severely wilted; leaf 

Garden balsam (Impatiens 

balsam ina): 

necrotic. abscission. b. ____ do _________________________ b. ____ do _____ _____ ____________ ___ b. ____ do _________________________ b. Do. 

55 ppm Au ________________________ 33 ppm Au ________________________ <0.8 ppm Au _____________________ 6.6 ppm Au. 

Rooted ______________________ a. Leaves turgid ______ ______ ______ a. Leave~ turgid __________________ a. Leaves turgid ___________ _____ __ a. Leaves turgid. 

b. Leaves turgid; roots necrotic ___ b. ____ do ____ --------------------- b. ____ do ___ ---------------------- b. Do. 39 ppm Au ________________________ 2.7 ppm Au _____ ___ ___ __ _______ ___ 0.9 ppm Au _______________________ 3.3 ppm Au. 

Not rooted __________________ a. Leaves moderately wilted; a. Leaves turgid ___ ________ ____ ___ a. Leaves turgid __________ ________ a. Leaves turgid. 

slight necrosis. b. ____ do _________________________ b. ____ do _________________________ b. ___ _ do _____ ____________________ b. Do. 

160ppm Au ___ ___ _______ _____ _____ 45 ppm Au ________________________ <0.4 ppm Au _____________________ 28 ppm Au. 

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ABSORPTION OF GOLD BY PLANTS B21 

Nonradioactive gold thiosulfate 'vas present in small amounts in 

rooted plants, but the radioactive compound was not shown in the autoradiographs. Large amounts were indicated in unrooted cuttings used 

in both experiments. 

SUMMARY 

1. If plants can absorb a particular sol or solution of gold, a sufficient 

amount enters the leaves to produce a positive autoradiograph and to 

be measured by atomic absorption analysis even though severe wilting and necrosis of stems and leaves occur within 24 hours after the 

plants have been placed in the solutions. 

2. Colloidal Au198 reduced by glucose and sodium oxalate could 

neither pass through root membranes nor enter the cut vascular systems 

of the experimental plants. The tests indicated, however, that colloidal 

gold precipitated from a gold chloride solution probably enters the 

vascular systems of cut stems and is transported into the leaves. 

3. Contact of gold chloride with cell membranes of roots, cut stems, 

and cells of the vascular system causes a reduction of the. compound 

and precipitation of the gold on the cell surfaces as a blue deposit of 

colloidal gold. This reaction limits or prevents the absorption of gold 

chloride by rooted plants. 

4. Despite the extreme toxicity of concentrated solutions of radioactive gold cyanide to all Impatiens, leaves of all plants in these solutions contained radioactive gold. Solutions of low Au198 cont.ent, in 

contrast, were not toxic; plants in these solutions re,mained turgid and 

produced new root growth even though autoradiographs showed that 

Au198 was present in the leaves. Of all the solutions tested, greater 

amounts of gold were absorbed from gold cyanide solutions than from 

any other solutions. 

5. Radioactive gold bromide solutions were very toxic to Impatiens, 

and gold was precipitated from the solutions by onion roots. The nonradioactive solutions were toxic, and gold was precipitated from the 

solutions by impatiens roots; nevertheless, moderate to large (160 

ppm) amounts of gold were absorbed. 

6. Radioactive gold iodide solutions were severely toxic to all experimental plants. Radioactive gold was present, however, in the leaves of 

all Impatiens. The nonradioactive solutions were less toxic, and leaves 

of impatiens contained as much as 64 ppm gold. 

7. Radioa.ctive gold thiocyanate was toxic to unrooted outtings of 

Impatiens but was absorbed by both rooted plants and unrooted cuttings. Nonradioactive solutions were less toxic, but very small amounts 

of gold were absorbed from the solutions. 
B22 CONTRIBUTIONS TO GEOCHEMISTRY 

8. ·Gold thiosulfate solutions were only slightly toxic to all Impatiens 

but were not, or were only slightly, absorbed by rooted plants. Unrooted 

cuttings generally absorbed large amounts. 

9. The radioactive gold in the flax extract was absorbed by all Impatiens, but more was absorbed by the rooted than by the unrooted 

plants. This pattern of absorption resembles that which occurs in 

natural soil solutions. The concentration of the solution used was, however, very toxic to ail Impatiens. 

CONCLUSIONS 

Colloidal gold was not absorbed by the roots of plants used in these 

experiments. Of the solutions of gold that are most likely to occur in 

the root zone of the soil under natural conditions, gold cyanide is the 

most readily absorbed by roots and transported in largest amounts to 

the leaves. 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. 

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deposit: Vop. Geol. Pribaikal. Zabaikal, no. 3, p. 146-149 (in Russian). 

Bailey, L. H., 1937, Impatiens, in Bailey, L. H., ed., The standard cyclopedia of 

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ABSORPTION OF GOLD BY PLANTS B23 

Henry, R., Herczeg, 0., and Fisher, C., 1957, Une nouvelle methode de preparation d'Or colloidal radioactif: Internat. Jour. Appl. Radiation and Isotopes, 

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Malte-Brun, M., 1824, Universal geography: Bost,on, Wells and Lilly, v. 1, 635 p. 

Malyuga, D. P., 1964, Biogeochemical methods of prospecting: New York, Consultants Bur., 205 p. 

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Rankama, Kalervo, and Sahama, Th. G., 1955, Geochemistry: Chicago, Univ. 

Chicago Press, 912 p. 

Reynolds, E. S., 1931, Studies on the physiology of plant disease : Missouri Bot. 

Garden Annals, v. 17, p. 57-95. 

Rovira, A. D., 1969, Plant root exudates: Bot. Rev., v. 35, no. 1, p. 35-57. 

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