The potentisation process by which homeopathic preparations are produced raises the concern that these medicines have placebo effects only, since they theoretically no longer contain active molecules of the diluted substance. Plant models offer a method of examining the efficacy of homeopathically prepared solutions. This study examined the effects of homeopathically prepared gibberellic acid (HGA3) on the germination performance of barley (Hordeum vulgare L.) seeds. The effect of HGA3 (4-200 cH) on seed germination rate and seedling development was compared to that of the most commonly used form of gibberellic acid (GA3), 0.5 g l(-1), and control (distilled water). The extent and type of response was dependent on the vigour level of the seedlot. Treating seeds from three vigour groups in HGA3 consistently resulted in larger seedlings. High-vigour seeds treated with HGA3 4, 30 and 200 cH germinated faster, and roots of medium-vigour seedlots treated in HGA3 15 cH were longer. Biphasic effects of HGA3 were also demonstrated. As a plant model, germinating barley seeds successfully demonstrated the ability of HGA3 to produce a biological response.
tests appears to be directly related to the condition of the seedbed environment (Egli and TeKrony, 1996). Emergence of soybean [Glycine max (L.) Merr.] seedlings in theKnowledge of the precise causes of emergence failure field is frequently less than predicted by standard germination, but the causes of this emergence failure are not well understood. This and their relative importance is lacking, and would idenstudy explored the influence of soil pathogens and seed vigor on tify those factors in the soil environment which need to soybean seedling preemergent growth and emergence. Seed from six be countered or modified if emergence is to be successseedlots, representing a range in seed vigor, were planted as pregermifully predicted and achieved. Such knowledge may also nated and as dry seed into sterile and pathogen-infested soil maincontribute to the development of improved vigor tests tained at a constant soil water potential (Ϫ0.005 MPa). Final emerwith which to identify seedlots most likely to be tolerant gence (FE) and emergence rates from two planting depths (25 and of adverse soil conditions. mm) were recorded under ambient greenhouse conditions. OnceEmergence responses to seedbed conditions have prethe FE stage had been reached, nonemerged seedlings were exhumed, viously been examined primarily in prevailing field conand classified as stunted, abnormal, or dead. The FE of the high-and ditions, as opposed to controlled conditions (Hegarty, medium-vigor seedlots was always higher than the low-vigor seedlots, and the advantage was greatest under stressful conditions (deep plant- 1979; Halmer and Bewley, 1984; Finch-Savage and Pill,ing, nonsterile soil). The FE was always lower in nonsterile than sterile 1990). Few attempts have been made to distinguish be- soil. Seedlings emerged more slowly from deep plantings and whentween the effects of the seedbed environment, seed qualpathogens were present, and FE decreased as emergence was delayed ity, or soilborne pathogens on germination sensu stricto, in nonsterile soil. This relationship became more pronounced with and on preemergent growth. In fact, the two terms are low vigor seed. Planting pregerminated seeds always resulted in higher often erroneously used interchangeably, yet the two are FE than dry seeds, but it did not eliminate emergence failure. Abnorbiochemically distinct phases of growth (Perino and mal seedlings accounted for most of the emergence failure in sterile Cô me, 1991), with potentially different responses to spesoil, but the lack of germination or of growth immediately after germicific environmental conditions. The purpose of this study, nation was also important in nonsterile soil. Lack of germination alone therefore, was to investigate the nature of the relationtherefore does not account for lack of emergence; postgerminative, preemergent growth may be more important.
Emergence of soybean [Glycine max (L.) Merr.] seedlings in the field is frequently less than predicted by standard germination, but the causes of this emergence failure are not well understood. This study explored the influence of soil pathogens and seed vigor on soybean seedling preemergent growth and emergence. Seed from six seedlots, representing a range in seed vigor, were planted as pregerminated and as dry seed into sterile and pathogen‐infested soil maintained at a constant soil water potential (−0.005 MPa). Final emergence (FE) and emergence rates from two planting depths (25 and 60 mm) were recorded under ambient greenhouse conditions. Once the FE stage had been reached, nonemerged seedlings were exhumed, and classified as stunted, abnormal, or dead. The FE of the high‐ and medium‐vigor seedlots was always higher than the low‐vigor seedlots, and the advantage was greatest under stressful conditions (deep planting, nonsterile soil). The FE was always lower in nonsterile than sterile soil. Seedlings emerged more slowly from deep plantings and when pathogens were present, and FE decreased as emergence was delayed in nonsterile soil. This relationship became more pronounced with low vigor seed. Planting pregerminated seeds always resulted in higher FE than dry seeds, but it did not eliminate emergence failure. Abnormal seedlings accounted for most of the emergence failure in sterile soil, but the lack of germination or of growth immediately after germination was also important in nonsterile soil. Lack of germination alone therefore does not account for lack of emergence; postgerminative, preemergent growth may be more important.
Selection on known loci affecting quantitative traits (DSQ) was compared to phenotypic selection index for a single and a two-trait selection objective. Two situations were simulated; a single known quantitative locus, and ten identified loci accounting for all the additive genetic variance. Selection efficiency of DSQ relative to traitbased selection was higher for two-trait selection, than was selection on a single trait with the same heritability. The advantage of DSQ was greater when the traits were negatively correlated. Relative selection efficiency (RSE) for a single locus responsible for 0.1 of the genetic variance was 1.11 with heritabilities of 0.45 and 0.2 and zero genetic and phenotypic correlations between the traits. RSE of DSQ for ten known loci was 1.5 to 1.8 in the first 3 generations of selection, but declined in each subsequent generation. With DSQ most loci reached fixation after 7 generations. Response to trait-based selection continued through generation 15 and approached the response obtained with DSQ after 10 generations. The cumulative genetic response after 10 generations of DSQ was only 93% to 97% of the economically optimum genotype because the less favorable allele reached fixation for some loci, generally those with effects in opposite directions on the two traits.
Infection of soybean [Glycine max (L.) Merr.] plants with Soybean mosaic virus (SMV) has been reported to enhance Phomopsis spp. seed infection, which reduces seed quality. The objective of this study was to determine the influence of SMV on Phomopsis spp. seed infection and seed germination and vigor. During 1995 to 1997, plants of two SMV‐susceptible cultivars (Clark and Williams) and their SMV‐resistant isolines (L78‐434 and L78‐379, resistant to SMV strains G1‐G6) were mechanically inoculated with SMV (G2 strain) at growth stages V4, V8 or R2, and Phomopsis spp. inocula were applied to all plants. Seeds harvested from SMV‐resistant isolines were consistently SMV free, whereas seeds from SMV‐inoculated susceptible cultivars accumulated SMV in seedcoats. Although environmental conditions were favorable, the incidence of Phomopsis spp. seed infection was consistently less than 12% in SMV‐resistant plants, and up to 14‐times greater in SMV‐inoculated susceptible plants, with primary infection occurring after seeds reached physiological maturity (at or after yellow pod stage). Seeds from SMV‐resistant isolines had high average standard germination (88%) and higher vigor (67% accelerated aging; 7 mS m−1 g−1 conductivity), whereas seeds from SMV‐inoculated susceptible cultivars had low standard germination (48%), low vigor (30% accelerated aging; 13 mS m−1 g−1 conductivity). Thus, infection by SMV at or before growth stage R2 increased the susceptibility of soybean seed to Phomopsis spp. infection, and resulted in poor seed quality and low vigor.
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