Diagnosis of Viability and Germination
Seeds with optimal seed quality germinate quickly and uniformly, resulting in vigorous seedlings with good potential to establish. However, seeds do not always germinate properly due to a poorer quality, which can be for various reasons. The first reason is when seeds are not optimally viable as a result of adverse environmental factors during seed development or harvest, for example infestation with insects while on the mother plant. The second reason why seeds do not germinate and appear to be unviable is if they are dormant. Such seeds do not complete germination, yet they are fully capable to do so if dormancy is broken. A classical germination test without a dormancy-breaking treatment would underestimate the viability of these seeds. Alternative tests would characterise them as dormant, e.g. expression of genes associated with dormancy or germination can be used to distinguish primary dormant seeds from seeds that have lost dormancy (Fig.1). The third reason is the loss of viability due to ageing of seeds. Like any living organism, seeds get older and lose their capacity to germinate. The more adverse the storage conditions, the faster seeds lose viability. Despite the fact that seeds are stored under optimal conditions in the seedbank, they will still lose viability, albeit slower.
Development of additional tests to assess the viability of seeds contributes to a better estimation of the quality of these seeds. These tests are part of the output of the research projects that address the above issues in seed quality. Developing a better understanding of underlying mechanisms will result in better diagnostic tests.
(Left) Seeds of Arabidopsis thaliana Cvi that have lost dormancy (G) are characterised by low expression of two dormancy genes (ATS2, ATS4) and high expression of two germination genes (AtRPL36B, AtRPL27B). The two dormancy genes (ATS2, ATS4) display high expression in dormant seeds (D) that do not complete germination.
Contact: Dr Peter Toorop
See the Science Directory for a full list of projects included in this Theme
