ON-LINE MEASUREMENT OF PLANT GROWTH IN THE GREENHOUSE
For determination of fresh weight and transpiration of plants an electronic balance is used in a hydroponic system. Adding of nutrient solution up to a fixed volume keeps the system tare weight constant. This allows measurement of fresh weight changes from adding to adding. Between these times the system can be used as lysimeter and measurements of evapotranspiration are possible.
The hourly changes of plant fresh weight and evapotranspiration rate show an antagonistic daily course.
The second method, a CCD-camera and an image processing system, allows on-line measurement of leaf area. An evaluation of the relation between fresh weight and recorded leaf area gives the best accordance with an exponential regression equation. Modification of the initial equation for each growing period improves the accuracy.