Wurzelsterben der Tomate im Geschlossenen Hydroponischen System bei Unterschiedlichen N-Konzentrationen der Nährlösung

Different supplies of nutrients result morphological changes of the plant roots and in changes of activity. Often it is related with root death. Share of inactive roots in a total root system of tomatoes grown in hydroponics should be investigated for two cultivars (Lycopersicon lycopersicum cv. Counter, Karina) dependent on plant age in three variations of the nitrogen amount supplied (between 7 and 51 mmoll−1).First step of investigations was to produce evidence of the triphenyl tetrazolium chloride method to detect inactive roots of tomatoes grown in hydroponics. With this method the inactive part was determined in a fresh sample of about 0.5 g during a growing period of about 170 days at 4 in 1994 and 6 in 1995 sampling dates.The best position to draw a representative sample was the middle of a root system and not the border. In the first 60 days of the growing period the inactive part of the roots stayed constant, lower than 10 %. After this time the part increased significantly until the end of the growing time and summed up to almost 70 %. The results were the same for both cultivars investigated. The influence of the increasing N supply was in 1994 not significant but it was in 1995. In general with increasing N in the nutrient solution the inactive part increased, too. The results showed that especially at the end of the growing period with high plant age growers have to pay attention to the roots to save the uptake of nutrients and water with a reduced active root system.