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Part IV, continued:

 

Entry of antibiotics into plants

  The importance of antibiotic substances formed in thesoil, for plants, is determined primarily by the extent to which the former enterthe plants via the roots and by their activity within the plant.

  The question of whether antibiotic substances are capableof entering the plants is now answered in the affirmative. Vegetating plants absorbvarious organic substances through their roots including antibiotics formed by bacteria,actinomycetes and fungi. The absorption by plants of subtilin, gramicidin, pyocyanine,licheniformin, (antibiotics of bacterial origin), as well as streptomycin, globisporin,aureomycin, terramycin, grisein, griseofulvin, etc (substances formed by actinomycetes)has been experimentally established.

  Table 121 shows the degree of entrance of chemicallypure antibiotic preparations, from solutions into the plant, via the root.

Table 121
Assimilation of antibiotics by plants
(units per 1 g tissue)

Antibiotics

Wheat, roots

Wheat, stems

Wheat, leaves

Peas, roots

Peas, stems

Peas, leaves

Penicillin

150

60

60

150

80

100

Streptomycin

100

20

20

100

20

30

Grisein (preparation No 15)

120

30

30

150

20

40

Mycetin

100

5

0

100

10

0

Subtilin

300

0

0

80

10

5

  Penicillin enters the plant at the fastest rate andin the largest amounts, followed by grisein and streptomycin. Mycetin subtilin andgramicidin enter in small amounts and do not travel high up in the plant.

   Aureomycin, terramycin, globisporin and many otheractive substances enter readily into the plants.

  Plants absorb from the substrate not only chemicallypure preparations but also crude antibiotics, in the form in which they are excretedby their producers. We added a liquid containing antibiotics to a culture solutionand grew plants in it. After a certain time one could detect antibiotics in the tissuesof the latter (Table 122).

Table 122
Uptake of crude antibiotic substances from culture fluids by plant roots
(units/ml)

Microorganisms producing antibiotic substances

Introduced into the soil

Found in wheat roots

Found in wheat leaves

Found in pea roots

Found in pea leaves

A. streptomycini

250

60

30

80

40

A. aureofaciens

600

120

50

100

40

A. grisseus strain 80

100

20

25

50

25

Bact. nitrificans

120

45

10

40

10

Bact. fluorescens

200

40

5

40

35

Bact. denitfricans

90

10

10

15

5

  Antibiotic substances enter plants from solid substrates,directly from soils.

  In our experiments (Krasil'nikov 1951 a; 1952 b, c;1953 c; 1954 a) we have tested various antibiotics formed by bacteria, fungi andactinomycetes-antagonists. Chemically pure preparations were introduced under adultplants in containers with sand or soil and their concentration was determined aftergiven time intervals on the root tissues and aerial organs. The experiments wereperformed both under sterile and nonsterile conditions of growth. In Table 123 aregiven the data from the experiment with the sterile sand substrate. Streptomycin500 units and grisein (preparation 15), 500 units were introduced per 1 g of substrate.

Table 123
Entrance of antibiotics into plants from sterile substrates
(units/g of tissue)

Antibiotics

Plant origin

Kidney beans in sand

Peas in sand

Wheat in sand

Kidney beans in soil

Peas in soil

Wheat in soil

Grisein Root

150

250

100

80

70

50

Grisein Leaves

80

120

60

50

40

20

Streptomycin Root

220

160

120

100

80

30

Streptomycin Leaves

100

80

40

40

40

40

  As can be seen from the table, antibiotics enter intothe plants via the roots in quite large quantities. They are found in roots, stemsand leaves for 10 days and more.

  In experiments performed with sterile soil (Moscowarea podsol) the same results were obtained. The antibiotics, globisporin, 500 unitsand grisein, 800 units were introduced per 1 g of substrate. Peas, kidney beans andwheat were grown on this soil. Analyses have shown, that globisporin was preservedin soil for 30 days and grisein for 40 days. During this time they penetrated throughthe roots and into the plants in smaller or larger quantities (Table 123). The rateof entry of antibiotics from sterile soil was only slightly less than the rate ofentry from nutrient solutions or from the sand substrate. After a few hours (6-10)the antibiotic substances could be found in the roots and in the lower parts of thestem.

  Our experiments have shown, that antibiotics are alsoabsorbed by plants from natural nonsterilized soil. The same antibiotics, griseinand globisporin, were introduced into vessels with podsol soil under adult plants(wheat and kidney beans) in doses of 800 units/g. After 24 hours and sometimes evenlater we detected these antibiotics in the tissues of the roots and aerial organs(Table 124).

Table 124
Entrance of antibiotics into plants from nonsterile soil
(units/g of tissue)

Antibiotics

Kidney beans, roots

Kidney beans, leaves

Wheat, roots

Wheat, leaves

Peas, roots

Peas, leaves

Grisein

20

10

30

10

30

20

Streptomycin

30

10

20

6

40

20

Aureomycin

--

--

20

4

20

6

Terramycin

--

--

30

10

20

6

Control plants

0

0

0

0

0

0

  Plants also absorb crude antibiotics from the soil.We tested three native antibiotics formed by the actinomycetes No 290, 287 and strain"B." In the presence of the appropriate organic matter in the soil, thesecultures, as is shown above, form 30-120 u/g of antibiotic substances. When we grewpeas and wheat in such soil, we could detect the antibiotics in the tissues in small,but sufficient quantities which were large enough to inhibit growth of microbes sensitiveto them (Table 125).

Table 125
Assimilation of crude antibiotics from the soil by plants
(units/g of tissue)

Antibiotics

Peas, roots

Peas, leaves

Wheat, roots

Wheat, leaves

No 290

10

2-3

4

+

No 287

15

3

10

2

"B"

2

+

4

+

The "+" sign designates small quantities detected only qualitatively.

  Thus, in pea plants, 2-15 units/g antibiotics wereobtained and in wheat somewhat less. In some cases, when there is an abundant growthof antagonists which form large amounts of antibiotics in the soil (100-150 units/g),large quantities of the latter enter the plants-up to 20-30 units/g in the rootsand 10-20 units/g in the leaves.

  The zones of growth inhibition of the test organismaround pieces of tissues of the experimental plants may be seen in Figure 96. Aroundthe shreds of tissue of the control plants no such growth-inhibition zones are formed.

 

Figure 96. Entrance of antibiotics from the soil into plant tissues. Zones of lack of growth of bacteria around pieces of tissues:

1--roots; 2 and 3--stems (lower and upper parts); 4--leaves; 5--roots of control plant, grown in soil without antibiotics, the zone is missing.

 

  It should be noted that plants may not only absorbthe antibiotics that exist in the free state from the soil but also those adsorbedby soil particles. It was stated earlier, that a considerable part of the antibioticsare adsorbed immediately after their formation and become tightly fixed. Adsorbedantibiotics cannot be washed,out with water or with a number of organic solvents,even upon prolonged treatment. However, due to the activity of their root systems,the plants, are in the position to sever this, bond between the antibiotics and thesoil particles and to desorb and take up the antimicrobial substances.

  We introduced streptomycin, up to 2,000 units/g andmore into the soil (podsol, garden) sometimes to full saturation, and then rinsedthe soil with water until no more antibiotic was found in the elutions.

  After this treatment about 1,500 units of streptomycinper gram remained in the soil. Plant seedlings of peas or wheat were planted in suchsoil and after some time their tissues were analyzed for the presence of the antibiotic.Usually, after 3-4 days and often even after 30-40 hours streptomycin was found inthe roots, stems and leaves in amounts up to 10-15 units/g and more. As a rule, soilanalyses have shown the absence of the free antibiotic; the latter was probably inthe adsorbed state and was actively absorbed by the roots.

  Antibiotic substances entering plant tissues, enhancethe bactericidal effect of their sap and thus increase the resistance of the plantsto diseases.

  The more abundant the growth of antagonists in thesoil, the more antibiotic substances they produce, the more of the latter entersthe plants and the stronger the bactericidal effect of the sap becomes.

  The sap of plants which are grown in a sand substratewithout microorganisms and without humus is, according to our observations, lessbactericidal than the sap of plants which are grown in nonsterile soil rich in humus.

  We enriched the soil artificially with actinomycetes--producersof streptomycin, and we grew in this soil plants--peas and wheat. The sap of suchplants was tested for its bactericidal effect on Bac. mycoides and Staph.aureus. Death of the bacterial cells in the sap of the experimental plants followedafter 8-12 hours, and in the sap of the control plants which were grown in soil notenriched with actinomycetes, there was only suppression of growth, but death of thebacteria was not observed.

  Plants grown in soil well fertilized with manure orcompost had more active sap than the sap of plants taken from unfertilized soil.The sap of plants grown in a greenhouse (corn) was less bactericidal, than the sapof plants, grown in the open ground in the same soil (Krasil'nikov and Korenyako,1945 a). Eaton and Rigler (1946) observed increased resistance of roots of cottonplant to Phymatotrichum ornnivorum upon treatment of the seeds with carbohydrates.In these cases, according to the author, intense growth of bacterial antagonistsin the rhizosphere of the plants was observed.

  Kublanovskaya and Brailova (1954), studied the bactericidalproperties of the sap of the cotton plant in relation to the fungus Fusarium vasinfectumand found that its fungitoxicity toward the given fungus was less when the plantsgrew in soil with antibiotic substances than the fungitoxicity of the control plantsgrowing in soil without antibiotics. The coefficient of multiplication of the fungusin the sap of the control plants was: 13.6 in the germination phase and 11.8 in thephase of cotyledons; in the sap of experimental plants: 7.8 in the phase of germinationand 9.8 in the phase of cotyledons. As is seen, the antifungal properties of cotton-plantsap are strengthened at the expense of the antibiotic substances coming from thesoil. Accordingly, the plants morbidity due to wilt was less: in the control 96%of the plants were diseased, and among the experimental plants--only 18.4%. Enhancementof antifungal properties of plant sap was also observed by Kublanovskaya in fieldexperiments on plots fertilized with actinomycetal cotton-cake composts.

  Stapp and Spicher (1954, 1955) observed the appearanceof protective substance a in the sap of the potato in relation to Bact. phytophthorumduring the development of the plant, when the soils were enriched with microbialantagonists.

  The data given show that the plants absorb antibioticsubstances from the soil. Antibiotics may be absorbed by the plants not only fromsolutions of chemically pure substances but also from a complex organic mixture ofmetabolites, the microbial antagonist.

  Actinomycetes, bacteria and fungi which produce antibioticsubstances, grow in the soil in the rhizosphere of plants. They saturate this zoneor microfoci in the soil with the products of their metabolism, including antibiotics.The latter enter the plants through the roots and exert their action there. It isself-evident that the concentration of antibiotics in soil, when formed under naturalconditions, will be lower than the concentrations created upon artificial introduction.However, under natural conditions, these substances are constantly formed and thereforeone would assume that their entrance into plants is not stopped during the wholevegetative period.

  Having entered the plant tissues the antibiotic substancesprotect them against the penetration of microbial parasites, suppress the growthof those that have already invaded, produce or elevate the toxicity of the plantsap and thus elevate to a larger or smaller extent the immunological properties ofthe plant.

  In other words, microbial antagonists are factors whichincrease the resistance and insusceptibility of plants to infections.

 

Antibiotic substances as a therapeutic means in plant cultivation

  Suggestions on the possible use of antibiotic substancesfor medical purposes were made by Pasteur, Mechnikov and their contemporaries. Scientistsattempted to use bacterial cultures together with their metabolic products for curingthe sick. Fehlesein (1883) described a case of curing lupus by introduction of Streptococcuserysipelas into the patient's skin. Colley (1893) used the same organisms forthe treatment of a cancer patient. Pavlovskii (1887) introduced a culture of Pneumococcusinto the bodies of animals and so prevented them from being infected with anthrax.Bourchard (1889) used the metabolic products of Pseudomonas pyocyane againstanthrax. Manasein (1871) and Polotebnev (1872) used the green mold Penicilliumin treatment of patients. Many other specialists attempted to use microbial culturesfor the purpose of medical treatment. A special branch of medicine, bacteriotherapyeven came into existence (cf. Kashkin, 1952; Ermol'eva, 1946; Waksman, 1947; Waksmanand Lechevalier, 1953; Kohler, 1955; Korzybski and Kurylowicz, 1955 and others).

  All these investigations had no proper success andrecognition and were soon dropped. Only after active substances--penicillin, streptomycin,etc were isolated and chemically purified, did the antibiotic substances producedby microbial antagonists receive general recognition.

  Presently, many antibiotic substances, penicillin,streptomycin, aureomycin, terramycin, subtilin, etc are widely used in therapeuticalmedicine and veterinary science. This successful use of these preparations in medicinenaturally served as a stimulus for work on the use of antagonists and their metabolicproducts against infections of plants.

  In the foregoing chapter we have shown the beneficentrole of microbial antagonists, their inhibition of phytopathogenic organisms in thesoil and then protection of plants against fungal and bacterial infections. We notedthere that microbial antagonists remove phytopathogenic forms directly from the soiland by virtue of this alone protect plants from diseases.

  However, the antibiotic substances obtained from culturesof antagonists may be used for the removal of phytopathogenic organisms not onlyfrom the soil but also within the plant. In other words, these substances shouldbe used as curative remedies.

  What then should be the requirements, in this case,from the antibiotics?

  As in the case of treatment of human beings and animals,antibiotics used in plant growing should: 1) be active against the agent causingthe plant disease and have the ability to inactivate toxins; 2) should penetrateeasily into the plant tissues; 3) should not be inactivated too rapidly; 4) shouldexhibit antibacterial activity within the plant tissue; 5) should not be harmfulto the plants at concentrations which are toxic to bacteria.

  In addition, the method of use should be technicallypossible and all the measures should be economically profitable.

  The first point was, in principle, proven experimentally.It was established, that phytopathogenic bacteria and fungi are susceptible to theinhibitory action of antibiotics.

  As was noted above, for each phytopathogenic microbeit is possible to choose its corresponding antagonist and to obtain its antibioticsubstances. Among the immense variety of microorganisms existing in nature, producersof antibiotics against bacteria, fungi, actinomycetes, viruses, etc can always befound.

  Concerning the second postulate--the ability of antibioticsubstances to penetrate the plants, this question too was answered in the affirmative.In the previous chapter it has been shown that these substances easily enter intothe root system and proceed to the aerial parts. Antibiotics can also be introducedthrough the aerial organs--stems, leaves and seeds.

  The possibility of introducing drugs into plants viathe stem, was shown by Shevyrev in 1903. He introduced various antiseptics into fruittrees with the aim of killing parasites. The method developed by him is nowadaysoften used for extrarhizal nourishment of plants. This method is as follows: a holeis bored in the trunk of the tree and one end of a wick (of gauze or cotton) is placedin the hole; the other end is immersed in a bottle which contains the antibioticsolution; the antibiotic enters the trunk of the tree through the wick and spreadsto all parts of the plant.

  In grassy plants antibiotics may be introduced viathe stem by simply wetting it or smearing a paste containing the preparation on it.We used the first method. A wetted piece of cotton or gauze was wrapped around thestem of the plant and covered with wax paper, to prevent rapid desiccation.

  We tested the method of introducing antibiotic substancesthrough the trunks of trees on various varieties of fruit-bearing and decorativeplants and under different climatic conditions--in Crimea, Caucasus and Moscow (Krasil'nikovand Kuchaeva, 1955). Various antibiotics were introduced into the plants--penicillin,streptomycin, globisporin, aureomycin, terramycin, grisein and other chemically purifiedpreparations. In a few cases we also introduced crude antibiotic substances in theform in which they appear in the culture fluid.

  Experiments have shown that all these antibiotics canenter the plant via the trunk, but in different amounts and at different rates. Penicillinenters at the most rapid rate (see above). Most of the experiments on absorbabilitywere performed with it (Table 126).

Table 126
Entrance of penicillin into plants upon introducing it via the stem
(July-August 1954)

Plants

Age, years

Height, meters

Diameter of trunk, cm

Time of intro- duction of anti- biotic, days

Solution adsorbed, ml

Anti- biotic units adsorbed

Detected in lower branches and leaves

Detected in upper branches and leaves

Maple (acer platanoides K.)

15

3

8

5

20

200,000

-

-

Ash tree (Fraxinus chinensis L.)

8

4

7

5

15

150,000

-

-

Lime tree (Tilia cordata Mill.)

5

25

7

5

10

100,000

-

-

White acacia (Robina pseudo- acacia L.)

8

2.8

7

5

10

100,000

-

-

(Halimodendron argenteum Fisch.)

15

1.8

6.3

5

0

--

-

-

Cherry (Cerasus vulgaris Mill.)

9

4.5

6.5

4

430

4,300,000

+

-

Bird cherry (Padus virginiana Roem)

15

4

5.8

5

210

2,100,000

+

-

Apple (Malus domestica Borkh)

8

3.2

7.3

3

380

3,800,000

+

+

Peach (Persica vulgaris Mill.)

8

1.5

6.0

5

560

5,600,000

+

+

Apricot (Armeniaca vulgaris Lam.)

7

1.6

5.4

5

900

9,000,000

+

+

Sweet cherry (Cerasus avium Moench.)

7

2.1

6.1

5

165

1,650,000

+

+

  As seen from the table, various woody plants absorbdifferent amounts of penicillin. Some of them, as for example, cherry, sweet cherry,apple, peach and apricot trees absorb antibiotics in large quantities, others likemaple, ash tree and lime tree absorb little of it.

  The distribution of the penicillin within the plantalso differs. In some plants (cherry, apple, peach, etc) it moves quickly to allparts, into the branches and leaves of the whole crown; in other plants (bird-cherrytree and Halimodendron) it slowly reaches only the lower parts of the branchesand leaves and does not reach the upper part of the crown; in still other trees (maple,ash tree and lime tree) it cannot be detected in the leaves at all.

  The intensity of the uptake and the distribution ofantibiotic substances in the plant changes noticeably with changes in climatic conditions--temperature,air humidity, soil moisture, etc. The lower the temperature and the higher the humidityof soil and air, the slower is the uptake of antibiotics. For example, in May 1954in the Nikitskii Garden, when the average temperature of the month was 13.4°C the temperature of the soil 14.2°C and the relative air humidity 92%, peachesand apricots absorbed 45-50 ml penicillin solution each on the first day and during5 days--100-110 ml. In August, the average daily temperature of the air was 24.3°C the soil temperature was 23° C and relative air humidity was 41%, the sameplants took up 200-210 ml on the first day and during 5 days--about 1 liter of penicillinsolution (Table 127). In May the absorption of penicillin was 3-5 times less thanthat in August, although in the spring plant suction is usually higher.

Table 127
Intensity of extrarhizal absorption of penicillin by plants under various weather conditions
(the Nikitskii Botanical Garden, 1954) (in ml of absorbed solution of 10,000 unit / ml activity)

Plant

1st day

2nd day

3rd day

4th day

5th day

Total

May: temp of air 13.4° C, soil temp. 14.2° C, relative air humidity 92%

 

 

 

 

 

 

Apricot

45

30

20

10

5

110

Peach

50

30

10

5

0

95

Sweet cherry

35

15

5

1

0

56

August: sir temp. 24.3° C, soil temp. 23.0 C, relative air humidity 41%

 

 

 

 

 

 

Apricot

210

200

190

200

100

900

Peach

200

180

100

40

40

560

Sweet cherry

80

50

15

10

10

165

  We obtained similar data in experiments with birch(10 years old) under the Moscow climate. A globisporin solution was administered(activity 5,000 u/ml) to the same plant via the stem on dry and on rainy days. Tworepeated experiments were performed: the first in June and the second in August.The amounts of antibiotic absorbed during 5 days were: on dry days in June--1,500ml, in August--900 ml and on rainy days of the same months the corresponding absorptionwas 350 and 200 ml, i.e., 4.5 times less.

  In experiments with lemon trees in the orchard of theInstitute of Subtropical Cultures (Anaseuli) in the rainy period in September 1952,the antibiotic grisein was absorbed to such a low degree that the work had to bepostponed until drier weather set in.

  The rate of distribution of antibiotics within theplant corresponds to the intensity of its absorption. The faster, and the more antibioticenters, the sooner it is found in the different parts of the plant. In experimentswith plants of the Nikitskii Garden we introduced a penicillin solution into treesand the rapidity of its appearance in the leaves 'was measured. Each day after theintroduction of the solution 20-30 leaves were removed from the tree and analyzedseparately for the presence of the antibiotic in them. Table 128 shows the percentageof leaves in which the antibiotic was detected.

Table 128
Rapidity of the distribution of the absorbed penicillin in the tissues of plants
(the figures designate the percentage of leaves saturated with the antibiotic)

Plants

Quantity adminis- tered in mg

Lower part of crown after one day

Upper part of crown after one day

Lower part of crown after two days

Upper part of crown after two days

Lower part of crown after three days

Upper part of crown after three days

IN MAY:

 

 

 

 

 

 

 

Apricot

45

0

0

41.6

33.3

90

13

Peach

50

0

0

50

25

55

18

Sweet cherry

35

0

0

0

0

60

0

IN AUGUST:

 

 

 

 

 

 

 

Apricot

200

100

100

100

100

100

94

Peach

210

100

100

100

100

100

100

Sweet cherry

80

100

100

100

100

100

75

  In August in dry warm weather, the antibiotic is rapidlydistributed throughout the whole tree. It can be found everywhere a few hours afterits introduction. In May there was cool rainy weather in Crimea. The uptake of theantibiotic and its distribution in the tissues was very weak. Only 2 days after introductioncould one detect the antibiotic in the plant's leaves, and then only in some leaves.

  The entrance of the said substances into the plantsis connected with the physiological conditions of the latter. The more intense themetabolic processes of the plants, the more vigorous their growth, the faster arethe antibiotics absorbed. When the external factors slow down the growth of the plant,the inflow of antibiotics into the roots also slows down. It was noted above, ata lowered air temperature the uptake of active substances is much more sluggish thanat a higher temperature in the summer. The same was observed by Stokes (1954) inher work. She determined the rate of uptake of griseofulvin by plants at differenttemperatures. At 25° C the substance enters the plant 5 times as fast and inlarger quantities than at 10° C. She also observed the detrimental effect ofexcessive humidity on the uptake of the antibiotic. At a 56% relative humidity itsconcentration in the tissues is 4 times higher than that at a humidity of 91% anda temperature of 25° C.

  Antibiotic substances taken up by the root system,are transported via the xylem to the aerial parts, the leaves. If, however, the antibioticsare introduced through the leaf surface, their transportation is accomplished throughthe phloem, i.e., as in case of substances synthesized in the leaf.

  Antibiotic substances entering the plant, penetrateinside the cells and cause a certain effect there. In order to follow the penetrationof these substances into the cells we used antibiotics which were luminescent inultraviolet light. Mycetin and certain other substances belong to these antibiotics.

  We allowed the antibiotic solution to pass throughthe tissues of the plant, we then performed microscopic analyses of microtone slices.Mycetin first enters into the cytoplasm, staining the various granules and rodlikemitochondria and then enters the nucleus, where it reaches higher concentrationsthan in the cytoplasm

  Some of these substances at certain concentrationsinhibit nuclear division upon entering the cells.

  Pramer (1955) followed the penetration of antibiotics--penicillin,streptomycin and chloromycetin into the cells of the algae Nitella Clavata.These algae were immersed in a solution of the antibiotic for some time, were thenwashed thoroughly, and the cell juice which was squeezed out of the individual cellswas collected with a micro-pipette. In this juice the content of the antibiotic whichwas introduced into the algae was determined.

  It was found that streptomycin and chloromycetin penetratethe membrane, reach the inside of the cells, and spread throughout the protoplastgiving the latter bactericidal properties.

  Penicillin, according to the author, is not detectedinside the cells. It either does not penetrate them or, if it does, is immediatelyinactivated.

  Nielsen (1955) found that antibiotics formed by theplankton of water reservoirs suppress the photosynthetic activity of algae of theChlorella group.

  There are theories which state that upon introductionof various substances into the trunk of a tree, they spread in a sectoral fashion,corresponding to the vascular transport system.

  Taking this in account, we paid special attention tothe distribution of antibiotics in the periphery of the bark of woody plants. Theadministered antibiotic was determined in the leaves and branches located in variousparts of the crownaccording to sectors and circular rings-in the lower, middle andupper parts.

  Numerous analyses show quite clearly, that penicillin,streptomycin, grisein and other antibiotics are distributed more or less evenly throughoutthe crown of the plant. We observed no sectoral distribution of the substances introducedin fruit, ornamental or forest trees.

  Certain antibiotics enter the root system from aboveand travel downward. According to our observations, grisein possesses this property.When it is introduced into the stem or the trunk of a lemon tree it can be foundafter a certain time in the lower part of the trunk and in the roots. The tissuescontained: in the trunk, at the point where the substance was introduced 120 units/g,near the root 60 units/ g and in the roots-30-50 units/g.

  The method of administering antibiotics through theintact stem by the use of gauze and cotton bandages, was employed by us in experimentswith grassy plants and with shrubs; it was also tested with woody plants. Young branchesof garden roses, apple trees and pear trees, stems of peas and wheat were wrappedwith cotton (or gauze) wetted with a solution of penicillin, streptomycin, griseinor another preparation; after a lapse of some time, the plant tissues were subjectedto analysis. As the investigations have shown, these substances penetrated insidethe plants, but never accumulated in high concentrations. This method is thus hardlysuitable for wide use. However, it may be used for local therapy.

  Introduction of antibiotics through the leaf surfacehas been performed in experiments with woody and grassy plants. The leaves of theplant were either sprayed with a sprayer or wetted with cotton.

  The spraying of the crown of plants with antibioticsolutions, using a sprayer was employed by us in experiments with fruit trees: peaches,apricots and apple trees and with grassy plants; peas, corn, wheat, etc. Preparationsof penicillin, streptomycin and grisein in dilutions of 1:1,000-1:5,000 were used.After some time these antibiotics were determined in the tissues of leaves, branchesand stems. Before analysis the severed leaves and branches were thoroughly washedin water.

  Analysis showed the following amounts of antibiotics(in 1 gram tissue):

 

Penicillin in units / g

Streptomycin in units / g

Apple tree

up to 5

2-3

Sweet cherry

15

5-10

Peach

10

10

Apricot

40

20-40 (grisein)

Peas

up to 20-50

10-20

Wheat

5-10

2-10

  The greater the distance from the location of the antibioticadministration, the lower its concentration in the organs of the plant.

  Upon wetting leaf surfaces with pieces of cotton soakedin a solution, even more convincing results were obtained. Two to five hours afterthe application of the cotton bandages with the antibiotic, the latter could be detectedin the leaf tissue which were quite removed from the spot of its application as wellas in the petioles of leaves, and even in the tissues of the branches which bearthose leaves.

  The American specialists use antibiotics in the formof dust, spraying them on the crown of the plants. The dust particles reaching thesurface of the leaves, dissolve and penetrate into the tissues.

  It should be pointed out that in all the experimentswith the various methods of introduction of antibiotics, the antibiotics move inthe direction of the lower parts as well the upper parts of the plant. Upon introductionof a solution of penicillin or grisein through the trunk of an apricot tree, thesesubstances were detected in the branches, leaves and root tissues as well. The samewas observed with peas. A preparation of penicillin introduced through the stem surface,was subsequently found in leaves in the upper parts in a concentration of 5-10 units/gand in the roots, in a concentration of 3-5 units/g (Table 129).

Table 129
Distribution of antibiotics in tissues of peas upon their introduction through the stem
(u/g of tissue)

Antibiotics

Roots

Stems

Leaves

Penicillin

3-5

10-20

5-10

Grisein

3-5

10-15

3-5

Streptomycin

1-3

10-30

3-5

  Mitchell, Zaumeyer, Andersen et al., (1952, 1954) introducedantibiotics, applying them with lanolin paste. The paste with the antibiotics wasspread on the stem surface, and after some time the active substance was determinedin the tissues of branches and leaves. Brian, Wright et al., (1951) observed thepenetration of the antibiotic griseofulvin into plants. Leben, Arny and Keitt (1953)introduced helixin and antimycin into plants, and Hessayon (1951) introduced trichothecin--anantibiotic obtained from the fungus Trichothecium.

  Antibiotics can be used for the sterilization of infectedseeds. It is known that in plant seeds there are often phytopathogenic bacteria andfungi which are sources of plant diseases. In order to get rid of these agents, variouschemical substances are used--antiseptics. However, the antiseptics which inhibitthe growth of microbes also act deleteriously on the seed tissues and decrease theirability to germinate.

  The antibiotics, unlike the antiseptics, act selectively,inhibiting microbial metabolism without causing any harm to the seed embryo. Thesterilizing effect of antibiotics was tested by us on cotton seeds. It is sufficientto immerse the seeds for 4-8 hours in an antibiotic solution in order to kill themicrobes in the seed tissues (Krasil'nikov, Mirzabekyan and Askarova, 1951; Askarova,1951: Mirzabekyan, 1952).

  Blanchard and Diller (1951) treated leguminous seedswith aureomycin, allowed them to germinate and then determined the entrance of theaureomycin into the seedlings. The authors noticed a larger accumulation of the antibioticin the roots than in the upper parts.

  The effectiveness of antibiotics depends on their concentrationin the tissues. In turn, the concentration depends on the properties of the plants,especially on the properties of the antibiotic and also on external conditions.

  It was found that. when the solution of antibioticis concentrated, more of it penetrates the plant (Table 130).

Table 130
Degree of saturation of plants with antibiotics
(units/g of tissue)

Antibiotics

Introduced into substrate units/ml

Wheat roots

Wheat leaves

Pea roots

Pea leaves

Corn roots

Corn leaves

Penicillin

5,000

3,500

3,000

4,000

3,800

5,000

4,000

 

1,000

600

500

500

300

800

300

 

500

200

100

300

160

180

80

 

100

70

40

50

30

60

25

 

50

80

40

50

40

80

70

Grisein No 15

1,000

800

600

500

400

950

600

 

500

250

160

300

180

300

100

 

100

70

40

80

50

80

50

 

50

50

40

60

40

80

85

 

10

30

20

50

30

50

30

  Very high concentrations of antibiotics (penicillin--5,000u/ml), grisein--1,000 units/ml) have a toxic effect on plants. They begin to witherand guttation stops. Smaller concentrations are harmless; the plants develop normally.



 





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