UP Umweltanalytische Produkte GmbH offers the latest technology in measuring sapflow and has more than 10 years of experience in manufacturing sensors using the thermal-dissipation technique (see Literature 1).

Measuring sap flow is important for understanding plant water relations and therefore is often used for studies of

• irrigation
• agronomy
• tree water use
• water stress
• etc.

UP offers single sensors, customized sensors and turn-key solutions including dataloggers and power-supply.

The sap flow transports nutrients to the leaves and to active cells (LARCHER 1984). The big water-potential difference between the soil, the plant and the atmosphere as well as capillar power cause the sap flow from the roots to the leaves (ASKENEY, JOLY,DIXON 1894/95).

Transpiration depends on the water-potential in the leaves and meteorological parameters (Wind, Radiation, Humidity and Temperature) as well as on soil moisture. Sap flow/Transpiration starts in the early morning hours and has maximum values about midday. At predawn hours sap flow is almost null. Measuring sap flow is a key technique in understanding and regulating plant water relations.

Each sensor consists of two identical manufactured needles with copper-constantan-thermocouples (Type T) and a special heating wire. Both thermocouples are connected in a way, that the signal corresponds directly with the temperature difference of both sensor elements.

The two needles are installed one above the other into the sapwood. The top needle is heated using a constant current source (120mA). This results in a temperature difference between both needles depending on the sap velocity.

High flux transports the heat upwards and shows a low signal, various low flux (e.g. at night) causes the highest temperature difference (about 10-13 °C). This measurement principle was developed in 1985 from Dr. André Granier at INRA, Nancy (see Literature 1+2).

1. Granier, André (1985): Une nouvelle méthode pour la mesure du flux de sève brute dans le tronc des arbres, Ann.Sci.For., 1985, 42 (2), 193-200.
2. Granier A (1987): Mesure du flux de sève brute dans le tronc du Douglas par une nouvelle méthode thermique. Ann.Sc.For., Seichamps, 44
3. Schulze ED, Hall AE (1982): Stomatal responses, water loss and CO2-assimilation rates of plants in contrasting environments. In: Lange OL, Nobel PS, Osmond CB, Ziegler H (eds.) Encyclopedia plant physiol, vol 12B. Springer Verlag Berlin Heidelberg New York, pp 181-230.