Author
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NELSON, STUART - US Department Of Agriculture (USDA) |
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Submitted to: Seed Technology Journal
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/16/2018 Publication Date: 1/15/2019 Citation: Nelson, S.O. 2019. Radio-frequency electrical seed treatment to improve germination: a review. Seed Technology Journal. 19:1(7-24). Interpretive Summary: This paper is a review of the findings of research on the treatment of various kinds of crop seeds with radio-frequency (RF) dielectric heating to improve the germination and performance of such seeds. Most were treated at a frequency of about 40 MHz, but l0-MHz and 2,450-MHz microwave treatments were included in some studies. No improvement in germination was achieved with many kinds of seed, but many others responded favorably, either with increases in germination or accelerated germination. Particular success was achieved in the treatment of alfalfa seed and that of some other small-seeded legumes that exhibited hard seed, impermeable seed coat, problems. Responses among different kinds of seed varied widely. Some of the small-seeded legumes, such as alfalfa, red clover, and arrowleaf clover, responded consistently with increased normal seedling germination and reduced hard-seed content. Others, such as sweetclover did not respond nearly so well. Hard-seed percentages were markedly and consistently reduced in alfalfa seed lots with substantial hard-seed contents, and the RF treatments rendered the impermeable seed coats permeable in the region of the strophiole, where the seeds become permeable to water naturally in time. Several of the vegetable and ornamental species did not show any improvement as a result of RF electrical seed treatment, but some, such as okra, garden peas, and garden beans responded favorably. Germination of spinach was consistently accelerated. As a group, grasses did not respond very well. However, the germination of Kentucky bluegrass seed was accelerated by the RF treatments, and interesting germination increases were obtained with side-oats grama, annual ryegrass, and switchgrass. In general, seeds of woody plants and tree species did not respond very well, although germination was increased or accelerated in some of the pine species. Results with field crops such as corn, cotton, and wheat were mixed, with acceleration and increased growth being noted in some lots but not in others. These particular seeds normally germinate well, but increases in rate of germination and seedling development would be welcome improvements. Practical aspects of RF electrical seed treatment were discussed. Practical application of new methods must be justified economically, and some of the factors are difficult to evaluate. However, the increased germination achievable in some kinds of seed and the proven long-range safety of the treatment for alfalfa and sweetclover indicate that the method might be considered for further study and economic analysis where practical benefits might be realized. Technical Abstract: An historical background on electrical treatment to improve seed germination and seedling performance is presented. Studies on use of radio-frequency (RF) dielectric heating for increasing germination through reduction of hard seed percentages, i.e., increasing seed-coat permeability to water, are reviewed. Extensive studies on treatment of alfalfa seed with RF electric-field exposures for increasing germination through hard seed reduction and examination of seeds to explain effects of treatment are summarized. The influence of frequency, electric field intensity, seed moisture content, seed temperature, varietal variation and other factors are discussed, and aspects of practical application in the seed industry are considered. Experiments with RF treatment of seeds of sweetclover, other small-seeded legumes, cereals, vegetables, pine, and other woody plants and trees are also summarized. |
