Wageningen Seed Lab

Seeds

Seed germination and dormancy represent key ecological and agronomical traits that determine plant establishment in natural or agricultural ecosystems. Seeds are necessary for sustainable production of food, animal feed and bioenergy. At ~$30 billion annually, the seed trade contributes significantly to the global economy.

Our projects address both fundamental and applied aspects of seeds. We are interested in mechanisms by which seeds sense the environment and adjust their timing of germination so as to maximize the probability of survival. One such mechanism is seed dormancy. We also study the remarkable stress tolerance of seeds. We are interested in how seeds are able to withstand severe dehydration and how they can survive for prolonged periods (up to hundreds of years).

On the applied side we attempt to integrate fundamental knowledge of seed biology with applied aspects of seed quality. We are particularly interested in the genetic components of seed quality.

The significance of our research is in the understanding key events of seed dormancy and germination and other traits, but always with a view to the 'big picture', relating molecular and cellular events to the physiological changes that take place concurrently and in dependence of the (changing) environment.

Subthemes

1. The mechanism and regulation of seed dormancy and germination.
2. The molecular dissection of seed quality.
3. The mechanism and control of desiccation tolerance in seeds.
4. The biophysical basis of seed longevity.
5. Physiology of flower bulbs
   

Dormancy

We are interested in seed dormancy and germination and study these traits using variation that occurs in nature by means of accessions of Arabidopsis thaliana. Why are seeds and its germination so important. Seeds are the link between two successive generations of plants. Seeds allow the plant to survive periods in which conditions are not optimal to complete it’s life cycle, but also allow it to be transported to a new location. The timing of germination is of extreme importance, when a seeds germinates at moments or under conditions that the plant cannot complete its life cycle it will die. This timing of germination is controlled by seed dormancy.

Seed dormancy is an important adaptive trait that together with flowering time is a primary component of the different life history strategies of plants. Dormancy can be considered as a mechanism where growth and development is arrested, despite the presence of favorable environmental conditions for growth and development. Specific environmental and developmental triggers can overcome this arrest. These environmental factors can act during seed development on the mother plant, during seed storage (after-ripening) and in imbibed mature seeds (which might lead to germination in non-dormant seeds). We are interested to identify genes and pathways that control seed dormancy in nature.

Quality

Seed quality, or seed performance, is the sum total of a number of physiological principles related to important plant developmental processes, such as embryogenesis, growth, stress-resistance and the transition from a seed to an autotrophic seedling. Seed quality attributes include germination (rate and uniformity), dormancy, seed and seedling vigour (germination/growth under stress conditions), seedling dry weight, normal embryo- and seedling morphology, as well as the ability to develop into a normal plant.

Seed quality is largely established during seed development and maturation, as a result of, often complex, interactions between the genome and the environment. This mechanism is part of the normal adaptation of plants to a varying environment and is aimed at maximizing the probability of successful offspring. The molecular-genetic dissection of these seed processes and their relationship with seed and seedling phenotypes will identify the regulatory genes and signalling pathways involved and, thus, provide the means to predict and enhance seed quality. 

Desiccation tolerance

Desiccation tolerance is one of the most outstanding features found in the plant kingdom. Seeds that possess such attribute, the so-called orthodox seeds, can be dried and stored for many years without significant loss of viability. Seeds that lack this characteristic, the so-called recalcitrant seeds, represent a big challenge for those who need to keep them in seed banks for germplasm conservation purposes. In order to gain insight into the theme, we study physiological, cytological and molecular aspects of desiccation sensitivity in seeds of Medicago truncatula, a legume model, orthodox-seeded species. Germinated orthodox seeds can be a useful model system for studies on desiccation sensitivity based on the fact that upon germination, orthodox seeds lose desiccation tolerance progressively and become comparable to the recalcitrant types. 

Longevity

Seed deterioration during storage is an inevitable and irreversible process. The rate of seed deterioration depends on external factors (relative humidity and temperature) and internal factors (genetics and seed quality). Seed treatments (e.g. priming) can also influence seed storage potential. It is very important to determine the storage potential of each seed lot, prior to storage in gene banks, to anticipate the loss of seed quality during the storage period. The most common approaches in the prediction of seed storability are tests based on accelerated aging or controlled deterioration. However, both methods are time and labour consuming and sometimes have a low predictive value. For this reason there is a continuing interest in identifying new physiological, biochemical or biophysical characteristics of seeds as markers of seed longevity.