Graduate Thesis Or Dissertation
 

Physical characteristics of crownvetch (Coronilla varia L.) seeds associated with viability and hardseededness

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/jd473002t

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  • The use of crownvetch (Coronilla varia L.) as a forage crop might be increased considerably if seed with low hard seed content could be made available at reasonable cost. Since mechanical scarification damages a large percentage of crownvetch seeds, this study was initiated to find other ways of reducing hardseededness. Two approaches to the problem were studied: (a) separation of hard and soft seeds on the basis of differences in physical properties, and (b) boiling water scarification followed by separation of soft seeds after soaking in water. Attempts to separate hard and soft seeds on the basis of length and width were only partially successful. Long-narrow seeds contained up to 33% less hard seeds than short-wide seeds in some lots, but this relationship did not exist in other lots. When extreme width separations were carried out, the widest group of seeds were associated with high dead seed content in some lots. Dark-brown seeds contained more hard seeds than the intermediate and light brown seeds. Dead seeds tended to be concentrated in the light-brown fraction. Seeds that swelled during the first two hours of soaking in tap water were associated with high dead seed content. Some lots showed an almost complete absence of dead seed in groups that required longer than two hours to swell. Seed dormancy was nearly eliminated by soaking in tap water and redrying. Immersion for five seconds in boiling water reduced hardseededness without lowering the viability of soft seeds. The percentage of hard seeds remaining after a five-second treatment was further lowered by a second treatment, again without reducing viability. It is the abrupt change in temperature, rather than long exposure to high temperature, that is important in breaking hardseededness. The viability of hard seeds was high, but usually less than 100%. Soft seeds were successfully separated from hard seeds, after soaking in tap water, by making a size separation with round-hole screens. Techniques for boiling water scarification and separation of hard and soft seeds were developed.
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