What happens to a seed when it is left in the ground? This article explores several factors that can affect it, including the physical and physiological dormancy of the seed, photodormancy, and the impact of fungi.
Physiological dormancy
Physiological dormancy is the absence of any ongoing molecular changes within the seed. It is a process that occurs in most species of plants. When seeds are separated from the fruit, they enter physiological dormancy. Several studies have been conducted to study physiological dormancy.
Physiological dormancy is important for plant survival in harsh environments. It prevents germination of imbibed seeds until a certain set of environmental cues are triggered.
During physiological dormancy, the pericarp of the seed becomes a physical obstacle, preventing the germination of the seed. This is a good adaptation for many wild species. However, it may pose problems for some species.
The development of physiological dormancy occurs when a seed undergoes a hormonal imbalance. This hormonal imbalance results in the release of volatile by-products that are perceived by seed predators. The release of dormancy is a gradual process that takes several months.
Some seeds also develop morphological dormancy. Unlike physiological dormancy, morphological dormancy is characterized by the growth of the embryo after shedding.
Photodormancy
There are two types of seed dormancy, namely physiological and induced. Induced dormancy is a well-documented phenomenon whereas physiological dormancy is the subject of a more general discussion. In the latter, seeds typically only have a limited lifespan after shedding their husks. It should be noted that the best germination conditions require some form of external stimulation. A well-maintained soil is a must for optimal germination. If this isn’t a given, the seed should be in a cool environment. The temperature should be appropriate for the species.
Optimum conditions can be a bit of a lottery, assuming a seed’s luck is about as strong as that of a poker player. On the other hand, a well-nourished plant will typically produce seeds that are capable of germinating in a relatively short time span. Seeds with high levels of dormancy will likely be confined to a narrow range of locations. This is an important consideration for farmers who rely on a single crop for food security.
Fungi destroy seed
Fungi destroy seed and are responsible for many plant diseases. They enter plants through wounds caused by harvesting, pruning, and mechanical damage. Once inside the plant, fungi destroy the gametophyte, destroying the embryo and the endosperm. During the process, fungi also absorb nutrients directly from the tissue walls of the host.
Fungi can infect many different plants, including trees. Some fungi are symbiotic, while others are parasitic. The presence of fungi is often associated with poor quality seeds. However, some species may be helpful to the health of the plant.
Currently, there are over a million known fungal species, with fewer than 10% able to colonize living plants. In the future, the number of fungi in the world will likely decrease.
Many pathogenic fungi cause damping-off. Damping-off causes the death of newly emerged seedlings. Factors such as the pathogen populations, the susceptibility of the host, the environment, and soil pH all contribute to the extent of damping-off.
Fungi also cause seed rot. Various species of the fungus Rhizoctonia are responsible for this disease. Root rot lesions are also commonly associated with this fungus.
Regulations and stewardship of treated seed
The market for treated seed has been growing at an unprecedented rate in recent years. In fact, 2011 revenues for the industry in North America alone grew to over $1 billion. However, there are concerns about the impact of these products on the environment. This has led to an increasing amount of discussion about regulations and stewardship.
In response to these concerns, seed associations and manufacturers are stepping up their efforts to improve the stewardship of treated seed. One example is a joint effort by the ASTA and CLA to compile and publish an up-to-date guide on the subject.
This Guide is available as an online interactive tool. It provides a comprehensive list of resources that can be used to educate and train seed companies. As well, it includes links to state and national agricultural associations.
While this guide is not exhaustive, it does contain important information. Many of the topics it addresses are essential to farmers and seed companies.
