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Last update: May 2021

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Biosensors for tree water status

The Water for agricultural purposes becomes a more expensive rarity. It is high necessary for agriculture to find new environment friendly irrigation techniques. At PIAF, biosensors for plant water status are being developed. The purpose is to fit water supply to tree real water requirements. It is the tree itself which directly guides (drives) its irrigation. Tests in orchards have shown that biosensor use allows a 30% irrigation water amount reducing, together with fruit production quality increasing.

Sap flow


Sensor installation
Sap flow sensor


This sensor measures the ascending sap amount which passes through the trunk. This water amount is drawn by the roots from the soil and evaporates at leaf level. So this sensor allows to measure the water which is consumed by a tree in a day, meaning also the exact water quantity to let into soil in order to balance the transpired water.


Ascending sap flow evolution in 10 days, on an irrigated tree and on a tree in drought conditions.

sap flow evolution in 10 days

Diameter variation

(INRA patent : PEPISTA)

sensor for the tree bark daily micro- deforming


This sensor measures the tree bark daily micro- deforming (on a micron scale!). The bark dehydrates and tenses when the tree transpires or is subjected to water stress. The amplitude of this contraction is an tree water status indicator. It is actually the most used sensor for guiding tree irrigation in orchards.


Bark micro-deforming evolution on an irrigated tree and on a tree in drought conditions.

Bark micro-deforming evolution : irrigated tree and tree in drought conditions.



Acoustic Drought Stress Monitor (AEs)

sensor for the ultrasonic emissions


The water stress can lead to the sap column breaking inside the wood conducting vessels and cause a gaseous embolism.. This sensor detects the ultrasonic emissions, emitted in case of water column breaking. It allows to defining the water stress threshold which must not be overrun in case of drought.


The daily evolution of acoustical emission number of irrigated or in dryness condition trees.


Daily evolution of acoustical emission number of irrigated or in dryness condition trees



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