Final answer:
Seed dormancy is a plant adaptation to survive in arid conditions by allowing seeds to remain viable over extended periods. The three types of dormancy caused by desiccation are physiological dormancy, physical dormancy, and combinational dormancy. These mechanisms let seeds wait for optimal germination conditions, contributing to species propagation through time.
Step-by-step explanation:
The concept of seed dormancy is an essential adaptation in plants for survival in arid or unpredictable environments, allowing seeds to remain viable until the right conditions for germination arise. There are three main types of dormancy caused by desiccation in seeds:
- Physiological dormancy: This is when the seed has internal conditions that prevent germination even if external conditions are favorable. It often requires a specific trigger to overcome, such as temperature fluctuations or light exposure.
- Physical dormancy: This occurs due to the presence of a hard seed coat that is impermeable to water and gases, thereby preventing germination until the coat is broken down or compromised through processes like scarification.
- Combinational dormancy: This type of dormancy involves both physiological and physical mechanisms that prevent germination. The seed may require multiple conditions to be met before it can germinate, such as breaking the seed coat and also changing internal hormonal levels.
These mechanisms are not only adaptations for surviving in dry conditions but also allow for temporal dispersal, much like animal offspring can disperse through space. Some plants have developed these forms of dormancy to cope with environments that only sporadically provide the necessary conditions for growth, such as deserts where rainfall is infrequent.