Continuous shoot growth monitoring in hydroponics

A weighing apparatus for automatic recording of fresh weight of shoots of spinach plants ( Spinacia oleracea L., cv. Subito) growing in nutrient solution is described. The system was tested for 17 days in a controlled environment and enabled the determination of the relative growth rate (RGR) of the shoot fresh weight. Results from three consecutive growth experiments demonstrated diurnal fluctuations in the relative growth rate of the shoot fresh weight. In general, relative growth rates were between 0.32 and 0.36 day^?1 16 days after sowing and decreased to between 0.11 and 0.18 day^?1 during the 12 following days. The variance between three replicate growth curves was compared with the variance of a growth function fitted through destructively obtained spinach shoot weight data.