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Vocabulary
- Calcium (Ca) is an essential element of cell walls. It is an important element to prevent the development of pathogens in plant cells. In fact, calcium deficiencies can cause premature fall of flower and buds. It also causes tip-burns on some plants.
- Tip-burn is a nutritional problem that most affects lettuce crops. Tip-burn are terminal leaf necrosis due to calcium deficiency. It is also a common issue affecting tomato crops.
Calcium circulation in the plants
In fact, calcium circulates inside the plant only via the vessels of the xylem (see picture below). From the roots to the leaves, calcium follows the flow of water used for transpiration. When the leaves at the top of a plant do not transpire enough, they do not get enough calcium. This creates a deficiency that weakens the plant.
Legends below:
1 = Water molecules captured by the roots passively and entering to the xylem tissues
2 = Column of water allowing molecules to adhere and circulate from the roots to the top of the plant
3 = Contact with stomates (pores), when the water molecules evaporate it creates tension (pulling force) in the water column
Stimulating foliar transpiration
Leaf transpiration is directly related to the photosynthetic activity of the plant. Insufficient leaf transpiration can lead to calcium deficiencies.
This anomaly is directly related to a greenhouse climate that is potentially “too humid”. It can be linked to the climate control set-points or a lack of ventilation in the growing area.
In the case of lettuce, directing the airflow towards the heart of the plant will limit the accumulation of moisture in these fast growing areas. Some growers therefore use vertical flow air (VAF) blowers for hydroponic lettuce growing in greenhouses.
Conclusion
Leaf transpiration is directly related to the photosynthetic activity of the plant. An insufficient foliar transpiration can lead to calcium deficiencies.
For those reasons, it is important to pay attention to the climatic parameters in the greenhouse. The addition of circulating fans (HAF or VAF) are necessary to homogenize the air in the greenhouse limiting the accumulation of humidity in certain areas.
Sources:
Brûlure de la pointe en laitue (BEJO):
https://www.bejo.fr/magazine/brulure-de-la-pointe-en-laitue
Prevent Tipburn On Greenhouse Lettuce (Urban Ag News):
https://urbanagnews.com/blog/prevent-tipburn-on-greenhouse-lettuce/
Production de la tomate de serre au Québec:
https://www.agrireseau.net/documents/95590/production-de-la-tomate-de-serre-au-quebec-guide-technique-de-297-pages
Jones J. J., Zitter T. A., Momol T. M. & Miller S. A. (Eds) (2014). Blossom-End Rot. Dans Compendium of Tomato Diseases and Pests. 2e éd. APS Press. The American Phytopathological Society Press, St-Paul, Minnesota. p. 129.
