Stress:when is it (still) useful?

In the project ‘Stress: when is it (still) useful?’ a conceptual framework is made about different types of plant stress in a greenhouse cultivation. The aim is to get a better understanding of plant stress and to prevent the need for energy consuming actions when a plant is ‘out of balance’. What is plant stress?

Commonly it is considered as a negative situation. But plant stress is a neutral concept: a plant senses the change that disturbs the balance between plant and environment. The plant adapts to the new situation which leads to a new balance. That means that stress can be beneficial for a grower, but stress can also have a negative effect on the crop.

Growers are steering the crop continuously during cultivation, which is in fact induction of beneficial stress. Examples are the transition from long day lengths to short daylengths to induce flowering of chrysanthemum, or pruning tomatoes. These crop management actions induce the crop to develop in the desired direction of the grower. Negative stress reactions of the crop should be avoided like closure of stomates, too high temperatures or light intensities that damage the crop.

What happens in a plant in a stress situation? After perception of the change in the environment certain signalling pathways are activated and (hormonal) signals are translocated within in the plant that ensure that it adapts to the new situation. Insights in these processes can be helpful (in the future) to detect and avoid negative plant stress reactions in an early stage. Research showed that plants have a stress memory which in some cases can be passed on to the next generation. As a result, temporarily experiencing stress can ensure that the plant is more resistant to the same or a different types of stress in the future. This process is called ‘priming’. The use of ‘priming’ also potentially offers growers opportunities to grow crops that are more resistant to negative stress.

The cultivation method “Next Generation Growing” aims for balances in crop and greenhouse. That implies that climate conditions (temperature and light) can be dynamic if the aim is to achieve a stable ratio between assimilate production and consumption. A crop is permanently exposed to changes that can be useful, but can be negative if limits are exceeded. The question is which actions lead to useful stress reactions and when negative stress effects occur. The boundaries are not always clear and often appear afterwards. Monitoring plant balance or plant stress would be a helpful tool and could provide insight into crop status and take “Next Generation Growing” a step further. This makes it possible to continuously gain insight into the status of the crop, prevention of taking energy consuming actions which reduces use of energy, without negative consequences for growth, production and product quality.