Seed germination

This has serious implications for malting varieties of barley where a rapid and high level of germination is essential. Barley varieties which exhibit dormancy, but which are suitable for malting in other respects, require to be stored before being subjected to the malting process.

The causes of seed dormancy are usually related to their morphology and physiology. In some members of the family Leguminosae the seed coat or testa is hard and impermeable to water. A good example of this is found with white clover seeds which will not germinate to their full capacity unless the seed coat is broken in some way. This can be achieved by abrasion or the use of concentrated acids. This source of dormancy is not a problem with the grain legumes in temperate climates.

Premature harvesting of seeds can lead to immaturity of the embryo and cause dormancy in this way. Poor germination of a proportion of sugar beet seeds in a seed bulk can be attributed to this cause.

Dormancy in some seeds is attributable to the presence of germination inhibitors in the testa of pericarp. These inhibitors are water soluble and can be removed by washing or soaking the seeds in water for a short period. In sugar beet, the inhibitors are concentrated in the pericarp of the fruit and are mainly organic acids, e.g. gallic, vanillic and p-hydroxy benzoic. This is one of the causes of poor germination in sugar beet.

The temporary dormancy in barley grains is attributable to a need for "after-ripening" in storage. Wheat and oats also exhibit this kind of dormancy but to a lesser extent. This may lead to problems of establishment of autumn-sown crops sown after harvest of the seed crop, unless a suitable period of storage has elapsed. In contrast, this phenomenon of dormancy can be a useful attribute in preventing seed from germinating in the year in periods of high rainfall before harvest.

Some seeds are light-sensitive and will not germinate unless they are exposed to light when they are imbibed. This cause of dormancy is not a problem in crop plants (except for lettuce) but it is a common feature in weeds, e.g. dock.