Volume 7, No. 1, 1982

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(pp. 1-9)
Improving the Germination of Johnsongrass Seeds
Kar-Ling J. Tao1
Eight seed lots of Johnsongrass had a mean germination of 46% after a 35-day standard germination. The tetrazolium tests, however, indicated a mean germination potential of 71% for these eight seed lots. A 30-min scarification with sulfuric acid (95-98% ) induced nearly complete germination within 10 days.

The germination mean was 73% for acid scarified seeds. Seeds scarified between sandpaper resulted in similar germination levels, but testing results varied significantly among experiments. ATP content in imbibed seeds was increased prior to radical protrusion by acid scarification. Acid scarification not only shortened the testing time but also produced more uniform results than the standard germination method. Thus, the acid scarification procedure should be considered in the AOSA rules for testing johnsongrass seeds.
Additional index words: Sorghum halepense, Acid scarification.
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(pp. 10-22)
Germination Responses of Sweetclover Seed to Infrared, Radiofrequency, and Gas-Plasma Electrical Treatments1

S . O. Nelson, L. E. Stetson, D. W. Works, and C. A. Pettibone2

Six nonscarified seed lots of sweetclover, Melilotus of ficinalis Lam., and M. alba Medik., were exposed to infrared radiation, radiofrequency electric fields, and gas-plasma radiation to compare the effectiveness of the treatments in reducing hard-seed content. All three treatments were about equally effective. Significant increases in normal-seedling germination and corresponding decreases in hard-seed percentages were achieved, but substantial amounts of hard seed remained in all seed lots after treatment.

Treatments were generally more effective when seed moisture content was low. Results of greenhouse sand emergence tests on treated and control samples were similar to those obtained in standard laboratory blotter germination tests. Measured water sorption of seed samples also followed the same patterns as germination test results, since both reflected changes in seed coat permeability. Samples tested after 17 years in storage at 4o C and 50% relative humidity had generally higher normal seedling counts and much higher abnormal seedling and dead seed counts than they did in initial tests. However, significant increases in normal seedling germination and reductions in hard seed content were still evident after 17 years in storage as a result of the electrical treatments. Improvements in germination performance were not great enough or consistent enough to warrant serious consideration of the treatments for practical application.
Additional index words: seed treatment, hard seed, infrared radiation, dielectric heating, gas-plasma radiation, seed storage.
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(pp. 23-35)
CASAS (Computerized Automated Seed Analysis System): An Approach to the Analysis of Testing Seed1

D. Keys2

A computerized automated seed analysis system (CASAS) has been developed which enables an analyst to estimate physiological parameters of seed and compare the values obtained with standards for seed of known quality. The system classifies the sample as commercially ac­ceptable or substandard, based upon equivalence to a standard germination test. The system is designed upon the S-100 bus. System design, hardware, software, and applications are discussed.
Additional index words: seed analyzer, seed testing, microcomputer, laboratory automation, data acquisition, software.
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(pp. 36-59)
Dynamic Conductrometric Analysis of Peanut (Arachis hypogaea L.) Seed Leachate Using the CASAS (Computerized Automated Seed Analysis System)
R. D. Keys2

A Dynamic Conductometric Analysis of peanut seed (Arachis hypo­gaea L.) has been developed. The analysis is programmed into the CASAS (Computerized Automated Seed Analysis System), and requires a three hour time period. A linear model of total ionic leaching from the seed is derived from a sample under analysis, for comparison with a general population model for commercial acceptability based upon a 70% germination equivalence criterion. After initial startup and calibra­tion of the equipment, the analysis is under control of the CASAS.
Additional index words: Seed analyzer, Seed testing, Microcomputer, Software, Seed leachate, Seed electrical conductivity.
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(pp. 60-71)
Improving Germination of Skunkbush Sumac and Serviceberry Seed1
P. Weber, L. E. Wiesner and R.. E. Lund2
Skunkbush sumac (Rhus trilobata Nutt.) and serviceberry (Ame­lanchier alnifolia Nutt.) are native shrubs extensively distributed in the western United States which have achieved importance in revegetation of disturbed lands. Standard germination tests were performed on each species as outlined in the literature. Seed viability was determined with triphenyl tetrazolium chloride (TZ). Results indicated that special tech­niques would be required to affect the rapid germination needed in current seed testing programs.

Both species have hard or impermeable seed coats and embryo dormancy normally overcome by cold stratification or fall sowing. Results confirm that skunkbush sumac germination is promoted by 75 minutes acid scarification and that KNO3 or GA produce no additional response. Acid scarification for 30 minutes and a mixture of thiourea (TU) and benzyladenine (BA) as a media moisten­ing agent was beneficial to serviceberry germination. Analysis predicted maximum germination to occur with 300 ppm BA and 100 mM TU. An interaction of BA and TU on germination was observed at the lower concentrations.
Additional index words: Rhus trilobata, Amelanchier alnifolia, gibberellic acid, potassium nitrate, thiourea, benzyladenine, germination, dormancy.
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(pp. 72-77)
The Effect of Woodchip-Newspaper Mulch on Germination of Grass and Legume Seeds Under Laboratory and Field Conditions
James E. Brown, Joe B. M addox and Walter E. Splittstoesser2

Seeds of fescue (Festuca arundinacea L.) perennial ryegrass (Lolium perenne L.), sericea lespedeza (Lespedeza cuneata Dum.-Cours.), and red clover (Trifolium pratense L.) were germinated in a slurry of vari­ous concentrations of woodchip-newspaper mulch. The germination per­centage of all species except fescue was reduced in this media.

The water was removed from the mulch (leachate) and germination of red clover and lespedeza seed was reduced in the mulch alone. No reduction in germination with the leachate was noted. The mulch contained high concentrations of boron and germination of all species was reduced when germinated in similar concentrations of boric acid alone. Under field conditions, all species tested gave an equal amount of vegetative cover with all mulch rates. After 5 months, over 70% vegetative cover was obtained and this increased to over 90% in 1 year.
Additional index words: boron, clover, fescue, lespedeza, ryegrass.
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(pp. 78-83)
Density Separation of Seeds With Hexane and Chloroform
A. G. Taylor2, A. M. McCarthy3, and E. M. Chirco2:

A float-sink technique to separate seeds by density differences is de­scribed. Mixtures of hexane and chloroform were used to obtain solutions of 0.66 to 1.47 g/cc, respectively. Wheat (Triticum aestivum L. 'York­ star') and lettuce (Lactuca sativa L. 'Ithaca') seeds were separated into density fractions of 1.30 to 1.45 g/cc in 0.05 increments and 1.12 to 1.18 g/cc in 0.02 increments, respectively.   Seed protein content and density were positively correlated in wheat. No phytotoxicity was observed from the organic solvents. Seeds of five tree species were separated into two density fractions. The cutting test was performed to determine the percent filled seed. The more dense fraction in all species had the greatest percent filled seed.
Additional index words: specific gravity, seed protein.
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(pp. 84-96)
Reduced Steeping Time for the Conductivity Vigor Test of (Phaseolus vulgaris L.) Seed
H . M . Brouwer1 and J. C. Mulder2

The results of two experiments on the conductivity test for bean (Phaseolus vulgaris L.) seed quality are reported.

In the first experiment, the effect of reducing soaking time from 24 hr down to 0.5 hr was ex­amined by monitoring the conductivity levels of the leachate from 49 single beans. Correlations with 24 hr conductivity ranged from 0.78 at 0.5 hr to 0.96 at 9 hr. A 4 hr soaking time gave results consistent with the 24 hr test. In the second experiment, the standard germination test was compared for 10 bean lines with the 4 hr single bean conductivity test, and the germination test applied to the same beans after 4 hr soaking. Two lines with high germination in the standard test performed poorly in the other tests. Based on these results, the conductivity test should be a quick means of detecting poor quality seed lots, and both the conductivity and the soak/germination tests should complement the germination test in assessing potential field performance.
Additional index words: laboratory germination tests, seed quality assessment, leachates, soak germination test.
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(pp. 97-107)
Identification and Pathogenicity of Fusarium species Isolated from Surface-Disinfested Watermelon Seed

R. McLaughlin and R. D. Martyn1

Watermelon seeds from 32 commercially grown lots and from 5 lots obtained from locally grown fruits harvested from wilted vines in one field (PV lots) were surface-disinfested, dissected and the seed coat halves and cotyledons plated on Komada's selective medium. Forty-four isolates of Fusarium spp. were single-spored and identified as either F. oxysporum, F. solani, or F. moniliforme.

Commercial seed lots had lower infection levels than the PV seed lots. Fusarium oxysporum was isolated more frequently from seed coats than cotyledons, while an equal num­ber of F. solani and F. moniliforme isolates was obtained from each. Twenty-one of the seed isolates were screened for pathogenicity to water­melons in three different tests. All 21 isolates caused some necrosis of 'Black Diamond' seedlings on water agar plates and eight isolates caused severe necrosis. Four isolates caused a 5-day delay in seedling emergence from soil in flats in the greenhouse, while three isolates caused a decrease in seedling emergence. Only one isolate caused significant damping-off of seedlings. None of the isolates repeatedly caused vascular wilt in older plants.
Additional index words: seed pathology, Cucurbitaceae.
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