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IV. The National Seed Storage Laboratory

IV. The National Seed Storage Laboratory

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102



EDWIN JAMES



efforts of plant breeders, thousands of varieties, breeding lines, and

genetic collections have resulted. A large portion of these has also

disappeared because breeders often had no further interest in an old

variety that had been superseded by a better one. Yet there is no assurance that a variety of breeding line having a poor rating under prevailing circumstances would not have value in the future as new races of

pathogens develop. Potentially valuable breeding materials have often

been stored in a haphazard manner on office shelves, in desk drawers,

or in boxes in attics or basements, and eventually discarded.



FIG.4. Front view of National Seed Storage Laboratory.



Recognizing the inadequacy of seed preservation, the National

Research Council in 1946 recommended the construction of a National

repository for the preservation of valuable seeds. After 10 years of

groundwork by representatives of Federal agencies, State Experiment

Stations, and interested private concerns, justification for a National

facility was presented to the Congress. Congress appropriated funds for

the construction of the Laboratory, which began operations in the fall

of 1958. A front view of the Laboratory is shown in Fig. 4.

B. OPERATION

The Laboratory is a three-level structure. The ground floor houses

all the mechanical equipment. A standby compressor can be put into



PRESERVATION O F SEED STOCKS



103



operation to take over the refrigeration load of any other compressor

that breaks down. A diesel generator provides current for essentials

during prolonged power failure. The offices are on the second level and

the germination laboratory and 11 cold storage rooms are on the third

floor. The rooms in use are maintained at 40°F. and 32 percent R.H.

Should lower storage temperatures be required, three rooms can be

cooled to 10".

The 11 rooms are stocked with approximately 180,000 tin cans with

screw-type lids. The cans are not airtight but the exchange of air between the inside of the cans and room atmospheres is very slow and has

no effect on the seed moisture content during short changes in the R.H.

of the rooms. Steel is used for all seed trays and shelves to reduce fire

hazards.

To provide enough seeds for initial germination tests, periodic tests

while in storage, and disbursement of seed, we prefer to store a minimum

of 4,000 to 5,000 seeds of each accession. Where difficulties are encountered by the geneticist in obtaining large quantities of seed of

certain genetic stocks, we reduce our requirements to 500 seeds and

adjust our germination amounts and schedules accordingly. Only clean

soeds of high viability are acceptable for storage. Once seeds are

accepted, the Laboratory assumes responsibility for maintenance.

Documentation or descriptions giving the agronomic or horticultural

characteristics of the seed are required, These characteristics are entered

on our punch cards to enable us to retrieve definite genotypes.

If the seeds deteriorate while in storage, reincreases will be made

through contracts with growers. The grower will be required to produce

a new generation under isolation or by selfing or sibbing, depending on

the method of species pollination. Germ plasm identical to the original

seeds should still be in storage in future generations if we assume that

no mutations occur during storage.

C. KINDS OF SEEDSSTORED



Recommendations as to what constitutes valuable seeds have been

made as a guideline for the Laboratory. It is recognized that such a

definition will vary greatly depending upon the significance attached to

the present commercial value of the crop involved and the individual

research worker's evaluation, whether he be a geneticist, horticulturist,

agronomist, or pathologist. However, the following categories of crop

seeds are accepted by the Laboratory and are in accordance with the

policy under which it operates:

1. New varieties: All newly released varieties, whether of private,

public, or commercial origin, including reselections from varieties continuing in current use.



104



EDWIN JAMES



2. Current varieties: Varieties currently in use and under registration by respective crop group organizations, or otherwise documented

as to specific origin and distinguishing characteristics. In this group

would be included those varieties approaching obsolescence which might

be superseded by new varieties.

3. Open-pollinated lines: Stocks representing earlier varieties or

types of specific crops which have been or will be replaced in the

commercial field by hybrids.

4. Inbred lines: Parental lines of known genetic composition widely

used in combination for hybrid production.

5. Obsolescent germ plasm: Samples representing holdover material

from earlier research programs and of no immediate interest. This could

include varieties, selections, open-pollinated, inbred, and genetic stocks.

6. Plant introductions: These are stored at one of the Regional or

Federal Introduction Stations and can be transferred to the Laboratory

when their supplies exceed their working stocks or for which requests

are no longer received. World collections fall within this group also.

7 . Pathological hosts: Varieties or lines used as differential hosts for

the identification of pathogenic races or for the indexing of plant viruses.

8. Physiological lines: Seeds of plants used in physiological studies

or physiological assays.

9. Mutants and genetic stocks: Samples regarded as highly valuable

for genetic studies.

10. Indexing lines: Lines or varieties used for indexing plant viruses.

Except for No. 8 and No. 10, samples of all the above categories are

now in storage in the Laboratory.

Anyone may submit seeds for storage, but once accepted by the

Laboratory, the seeds become public property and are available to all

bona fide research men upon request, provided they are not available

elsewhere. The only exception to this rule is that in case a plant breeder

wishes to protect his release, he can request a 5-year “freeze” on the

distribution of his seeds.

D. CONTRIBUTIONS

TO SCIENTISTS



When adequate storage facilities are not available to the geneticist

or plant breeder, a considerable portion of his time must be applied to

routine increases of his stocks. An example is the world collections of

small grains, which were reincreased every 5 years. Now that a portion of

these collections is stored in the Laboratory, the reincrease schedule

can be extended for a minimum of 10 to 15 years. The services of the

Laboratory eliminate the short-term reincrease programs and give the

research man more time for breeding programs. His seed stocks are



PRESERVATION OF SEED STOCKS



105



protected against loss of viability, which is not always the case where

he lacks storage facilities. Some seeds have been sent to the Laboratory

with a germination of only 8 percent.

The Laboratory has the largest collection of germ pIasm in the

United States. As of October 1966 accessions totaled more than 52,000.

These provide the plant breeder with a very wide base for future

breeding programs. Cooperation on the part of plant breeders is necessary to widen this base, So far, requests for seeds have been infrequent,

but in future years I am sure they will increase. This prediction is based

on the fact that most requests have been for seeds of obsolete varieties

that have not been grown for many years. We have been able to fill many

of these requests because we store seeds of obsolete varieties whenever

they can be obtained.

The seeds stored in the Laboratory can serve as a foundation for

future genetic investigations into genetic shifts resulting from selection

pressures or possible climatic influences. Seeds stored at 40” would not

be expected to develop genetic changes and should be valuable for

future comparisons with those seeds which had been produced over

successive generations.

Planning of the Laboratory was projected into the future with

subsequent generations in mind. The bulk of the material now stored

may have little value in the future, but the preservation of one or two

lines that might be resistant to new virulent strains of pathogens may

result in the saving of a crop as well as paying for the building and

operation of the Laboratory.

REFERENCES



Anderson, J. A., and Alcock, A. W. 1954. Am. Assoc. Cereal Chemists, Monograph

Ser. 2, 515 pp.

Anonymous. 1964. California Seed Law and Regulations. State of California Dept.

Agr., Sacramento, California. Agr. Code, Sect. 914( 1 ) ( c ) and Admin. Code

Sect. 3864.

Bailey, C. H. 1940. Plant Physiol. 15,257-274.

Barton, L. V. 1961. “Seed Preservation and Longevity.” Wiley (Interscience), New

York.

Bass, L. N., Ching, Te May, and Winter, F. L. 1961. Yearbook Agr. (US.Dept.

Agr.) pp. 330-338.

Bautista, G. M., and Linko, P. 1962. Cereal Chem. 39,455-458.

Blakeslee, A. F. 1954. Ann. N.Y. Acad. Sci. 57, 488490.

Crocker, W. 1938. Botan. Rev. 4,235-274.

Crocker, W. 1948. “Growth of Plants,” pp. 28-66. Rheinhold, New York.

Crocker, W., and Harrington, G. T. 1918. J. Agr. Res. 15,137-174.

DAmato, F., and Hoffman-Ostenhof, 0. 1956. Advan. Genet. 8, 1-28.

Davis, N. D. 1961. J. Alabama A d . Sci. 3Z9251-254.

Davis, W. C. 1931. Plant Physiol. 6,127-138.



106



EDWIN JAMES



Davis, W. E. 1926. Boyce Thompson Inst. Plant Res. Profess. Paper No. 2.

Ewart, A. J. 1908. Proc. Roy. SOC. Victoria 21,2-203.

Grabe, D. F. 1964. PTOC.Assoc. Ofic. Seed Analysts 54,100-109.

Gunthardt, Helga, Smith, L., Haferkamp, Mary E., and Nilan, R. A. 1953. Agron. J.

45,438441.

Haferkamp, Mary E., Smith, L., and Nilan, R. A. 1953. Agron. J. 45, 434437.

Harrington, J. F. 1960. Proc. 1959 Short Course Seedsmen, Mississippi State Univ.,

pp. 89-107.

Harrington, J . F. 1963. Uniu. Calif. Agr. Expt. Sta. Bull. 792.

Holman, L. E., and Carter, D. G. 1952. Uniu. Illinois Agr. Expt. Sta. Bull. 553, 449496.

James, E. 1961. U . S. Dept. Agr. ARS 34-15-1.

James, E. 1962. Seedsmen’s Dig., December, 13, pp. 14, 70.

James, E. 1963. U . S. Dept. Agr. ARS 34-15-2.

James, E., Bass, L. N., and Clark, D. C. 1964. Proc. Am. SOC. Hort. Sci. 84, 527-534.

Kelly, C. F., Stahl, B. M., Salmon, S. C., and Black, R. H. 1942. U . S. Dept. Agr.

C~TC

1637.

.

Lantz, C. W. 1927. Am. J . Botany 14, 85-105.

Leggatt, C. W. 1929-30. Sci. Agr. 10,73-110.

Leggatt, C. W. 1933. Can. J. Res. 9, 571-573.

Linko, P., and Sogn, L. 1960. Cereal Chem. 37,489499.

Lynes, F. F. 1945. J. Am. SOC. Agron. 37,402404.

Moore, R. P. 1963. PTOC.Assoc. Ofic. Seed Analysts 53, 190-193.

Munford, R. S. 1965. PTOC. 1964 Short Course Seedsmen, Mississippi State Univ.,

pp. 144-156.

Navashin, M. 1933. Nature 131, 436.

Nichols, C., Jr. 1941. Genetics 26, 89-100.

Nutile, G. E. 1964. Crop Sci. 4, 325-328.

Owen, E. B. 1956. Commonwealth BUT.Pastures Field Crops Bull. 43, 81 pp. Commonwealth Agr. Bur., Farnham Royal, Bucks, England.

Oxley, T. A. 1948. “Scientific Principles of Grain Storage” Northern Publ. Co., Liverpool.

Peto, F. H. 1933. Can. J. Res. 9, 261-264.

Rhine, L. E. 1924. Botan. Gaz. 78, 46-67.

Robertson, D. W., and Lute, A. M. 1937. J. Am. SOC. Agron. 29, 822-834.

Struve, W. M. 1959. Dissertation Abstr. 19, 2222.

Thorneberry, G. O., and Smith, F. G. 1955. Plant Physiol. 30, 337343.

Zeleny, L., and Coleman, D. A. 1939. U . S. Dept. Agr. Tech. Bull. 644.



SILICA IN SOILS. PLANTS. AND ANIMALS

L . H. P. Jones and



K . A . Handreck



Division of Plant industry. Commonwealth Scientific a n d Industrial Research Organization.

University of Melbourne. Victoria. Australia



.



I Introduction .

. . . . . . .

I1. Factors Affecting the Silica Content of Plants .

A Soil .

. . . . . . . .

B . Species

. . . . . . . .

C . Transpiration .

. . . . . .

D. Nutrient Supply .

. . . . .

111 Silica in the Plant .

. . . . . .

A Distribution Among Plant Parts .

. .

B . Nature of the Solid Silica .

. . .

C Deposition in the Tissues .

. . .

IV Silica in Relation to Plant Growth .

. .

A . Is Silicon Essential? .

. . . .

B . Interactions with Heavy Metals .

. .

C . Interactions with Phosphorus

.

.

.

D . Resistance to Fungi and Insects .

.

.

E . Miscellaneous Beneficial Effects .

. .

V Silica in the Ruminant Animal .

. . .

A . Quantities Ingested

. . . . .

B . Fate and Effects of Solid Silica .

.

.

C Fate of Dissolved Silica

.

.

.

.

D. Silica Urolithiasis .

. . . . .

VI The Silica Cycle .

. . . . . .

References

. . . . . . . .



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Introduction



The object of this review is to consider various aspects of silica in the

chain from soil through plant to animal. The starting point is the soil

solution because it is the immediate source of the silica which is always

absorbed by soil-grown plants . This habit of plants of absorbing silica

was recognized by the earliest plant scientists and in the latter half of

the nineteenth century there were already claims and counterclaims

about the place of silica in plant nutrition . Although it is doubtful that

any plant physiologist today would place silicon in the list of essential

nutrient elements. there is nevertheless increasing evidence that silica can

107



L. H. P. JONES AND K. A. HANDRECK



108



produce beneficial effects on plant growth. For the most part these effects

have been observed amongst gramineous species and the best examples

are seen where silica alleviates manganese toxicity and improves resistance to fungal and insect attack. The gramineous species are also notable

for their relatively high silica content and they have been the subject

of most of the basic work on the uptake of silica and its forms in the

plant. Although this review of necessity places emphasis on gramineous

species it also includes some treatment of silica in legumes and other

dicotyledons which are notable for their relatively low silica content.

The presence of silica in pasture plants ensures that grazing ruminants

ingest rather large amounts of silica, most of which is in the solid form.

Apart from slight dissolution this silica is unchanged in passing along

the alimentary tract, and its known effects on the animal are physical

or mechanical. The dissolved silica which is absorbed from the alimentary tract is carried to the kidney and excreted in the urine. Although it

is normally excreted readily the silica is sometimes deposited to form

calculi or uroliths, which can cause serious economic loss, Some consideration is given to the etiology of siliceous calculi in sheep and cattle.

II.



Factors Affecting the Silica Content



of Plants



A. SOIL

It has long been recognized that plants of one species contain different concentrations of silica when grown in different soils. In order

to interpret the effect of soil on the uptake of silica it is first necessary to

present some facts about the reactions of silica in soils. In the last few

years five independent groups have concurrently investigated these reactions (Acquaye and Tinsley, 1964; Beckwith and Reeve, 1963, 1964;

Gifford and Frugoli, 1964; Jones and Handreck, 1963, 1965b; McKeague

and Cline, 1963a,b) and much of our present understanding of the

subject has been reviewed by McKeague and Cline (1963~).This recent

work followed the fundamental studies of Alexander et al. (1954) and

Krauskopf (1959), who showed that silica in solution is present almost

entirely as the simple molecule monosilicic acid, Si( OH),, at p H below

9. In a saturated solution of pure amorphous silica the concentration of

monosilicic acid is, at 25"C., 120 to 140 ppm. expressed as SiO,. The

solubility of silica is independent of pH in the range 2 to 9, but it increases sharply above pH 9 because of the formation of silicate ions.

The only work dealing specifically with silica in the soil solution, as

distinct from silica in aqueous extracts of soils, is that of Jones and

Handreck (1963, 1965b), who used a pressure cell to obtain solutions

from soils maintained at field capacity. They established that the silica



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