Stomas are pores made up of two cells called guard cells. Guard cells are hydraulic valves that make it possible to close and open stomata.
Stoma Opening and Closing
Water relationships in guard cells follow the same rules as in other cells: Water always moves from high potential to low water potential.
Guard cells can take up sugar, potassium and chloride ions. The increase in solutes allows water to enter through the protective cell membrane. As water enters, the volume of the cells begins to increase and encourages stomatal opening. On the other hand, chemical reactions can promote stomatal closure by providing signals to remove water and ions from water cells.
Changes in chemical reactions are often regulated by different factors that we manage within growing systems. Therefore, it is important to understand how different environmental factors can affect stomatal behavior, which can have a direct impact on photosynthesis, nutrient uptake and more.
Light, water content, temperature, mineral content and CO2 are some important factors influencing stomatal behavior.
Light
Light is one of the most important signals promoting stomatal opening, and the amount and quality of light can affect this process. Blue and red lights are associated with stomatal opening. In particular, blue light is considered the quality of light that promotes potassium movement within guard cells and creates conditions to promote water movement within guard cells through osmosis.
Water Content in Epidermal Cells
Water content from cells closer to the guard cells can also affect stomatal opening and closing. For example, low humidity can affect the water content of epidermal cells, reducing the water potential of guard cells and promoting stomatal closure.
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Heat
An increase in temperature causes the stomata to open. When the air temperature rises, it initiates a cooling mechanism by transpiration, which includes opening the stomata.
Mineral Content
Mineral content is another factor affecting stomatal behavior. Potassium is one of the most important elements associated with stomatal regulation. The osmotic pressure in guard cells changes depending on the Kios present in the cell in response to different signals. In addition, research supports that nutrient deficiencies can also affect stomatal opening. Nitrogen and Phosphorus deficiency are two elements that have been linked to dysfunctional stomatal behavior.
Carbon dioxide (CO2)
We know that stomata are responsible for taking up CO2 to initiate photosynthesis. Therefore, the CO2 concentration in the plant will also have an effect on stomatal behavior. As photosynthesis takes place and the CO2 inside the leaf begins to fall, the plant will open the stomata so that more CO2 can be fixed.
In growing systems, we have the power to manage all the variables that affect stomatal movements. Sometimes we tend to get used to very practical knowledge of system administration by following "recipes" on how to control environment variables. However, it's always important to go back to the basics to really understand what's going on with our plants. With a better understanding, all measurements and decisions taken in our systems will be more accurate.
Understanding plant production systems along with basic plant physiology will always be a great strategy for success in agriculture!