Seed dormancy may appear to be nothing more than a stumbling bar to the complete germination of an intact healthy seed under ideal conditions, but previous evaluations determined that it is one of the most poorly understood processes in seed biology.
There has been a great number of published material and substantial progress in understanding seed dormancy in the decade following these evaluations, which we summarise here. However, certain possible causes of ambiguity have been documented in the literature.
There has been some uncertainty in ecological research about the difference between seed dormancy and soil persistence.
Different perspectives on dormancy, such as whether light ends hibernation or encourages germination, have contributed to this. Much of the research in the physiological literature has used model organisms like Arabidopsis to take a molecular genetic approach.
Secondary Dormancy Evaluation:
A variety of strategies for inducing secondary dormancy in A are available in the laboratory. Imbibed seeds are often kept in the dark and subjected to temperature and/or osmotic stress treatments to induce secondary dormancy. In A. Thaliana’s research, the genotype is often employed, and mutant lines are readily available through stock centres. As a result, secondary dormancy induction is likely to be difficult to observe, as secondary dormancy induction is slower in accessions with low primary seed dormancy levels.
Secondary dormancy induction is aided by using seeds with residual primary dormancy levels, as stated above. Adjusting the parameters of the germination test, as in the case of secondary dormancy, can show it.
As a result, a seed batch that received a subsequent dormancy inducing treatment may sprout fully under favourable germination circumstances B but not under favourable germination conditions A, where conditions A are less favourable than conditions B.
As a result, germination condition A is better for detecting secondary dormancy. In A. thaliana, barley, and tomato seeds, increasing the temperature employed in the germination experiment has shown to be an effective method for revealing superficial primary and secondary dormancy.
Secondary dormancy is easier to induce in accessions that have greater levels of primary dormancy naturally, such as Landsberg erecta and, in particular, Cape Verde Islands. As a result, these accessions may be better for studying secondary dormancy.
Types:
There are two types:
i) Thermo dormancy: Dormancy caused by high temperatures.
ii) Conditional dormancy: A variation in the ability to germinate based on the time of year.
Advantages:
- Allowing germination only when climatic conditions are favourable for seedling survival, as in temperate fruit plants.
- Aided in the establishment of a “seed bank”
- Dormancy can also be used to schedule the germination of seeds to a certain season.
- Specialized dormancy conditions can help with seed disposal. For example, seed covering changes via a bird’s or other animal’s digestive tract.
Model for Secondary Dormancy Regulation:
In the end, both primary and secondary dormancy germination arrest is the consequence of internal signalling pathways responding to external circumstances. The genetic basis of the seed, as well as maternal environmental conditions such as temperature during seed development, dictate primary dormancy levels throughout seed maturity.
- The basic seed dormancy levels present in the seed trigger the germination arrest programme mediated by ABA upon imbibition of a dormant seed.
- After-ripening mechanisms in dry seeds are assumed to primarily entail oxidative reactions in reducing primary dormancy levels. After a period of oxidative events during the after-ripening phase, primary seed dormancy levels are reduced to the point where the germination arrest programme is no longer engaged under a given favourable seed germination situation.
- A paradigm for Secondary Dormancy Regulation, In the end, both primary and secondary dormancy germination arrest is the consequence of internal signalling pathways responding to external circumstances.
- The genetic basis of the seed, as well as maternal environmental conditions such as temperature during seed development, dictate primary dormancy levels throughout seed maturity.
- The basic seed dormancy levels present in the seed trigger the germination arrest programme mediated by ABA upon imbibition of a dormant seed. After-ripening mechanisms in dry seeds are assumed to primarily entail oxidative reactions in reducing primary dormancy levels.
Conclusion:
Dormancy is a state in which seeds/tubers do not germinate despite the presence of all necessary circumstances (temperature, humidity, oxygen, and light), and is caused by hard seed coat impermeability or a lack of supply and activity of the enzymes required for germination.
It is a significant limiting factor in the yield of many field crops. To overcome dormancy, organic material (seeds/tubers) is subjected to a variety of physical and chemical pretreatments. Some plant species have both physical and internal dormancy, making it difficult to offer high-frequency healthy seedling development, even though the sprouting of seeds/tubers sowed and the generation of healthy seedlings is a requirement for plant production.