Decrease of Yield of Cucumber by Non-renewal of the Nutrient Hydroponic Solution and its Reversal by Supplementation of Activated Charcoal.

Autotoxicity in Vegetables and Ornamentals and Its Control

“…In closed hydroponic culture without renew of the nutrient solution, we found that the fruit yield of cucumber plants decreased significantly in the late reproductive stage (2 weeks ahead of final harvest) and the growth was recovered by the biweekly renewal of nutrients or supplementation of AC to the nutrient solution (Asao et al, 1998a). Shrunken fruits were harvested from the plant grown in non-renewed culture solution (Fig.…”

“…Some aromatic acids also accumulated in the nutrient solution during hydroponic cultivation of tomato and had inhibitory activity on growth (Yu & Matsui, 1993). Asao et al, (1998aAsao et al, ( , 1999c demonstrated that a reduction in fruit yield in the late reproductive stage of cucumber was induced by root exudates and that the most potent inhibitor was 2,4-dichlorobenzoic acid. In a closed hydroponic culture of rose plantlets, root and shoot growth were reduced by root exudates (Sato, 2004).…”

“…Our research history started with the selection of cucumber cultivars suitable for a closed hydroponics system using bioassay with cucumber seedlings (Asao at al., 1998b). Experiments were conducted to clarify why fruit yield decrease during the late growing period of cucumber cultured in non-renewed hydroponic nutrient solution and results were suggested that root exudates had induced the decrease in fruit yield, especially by affecting young fruits, the decrease was reversible through removal of root exudates by AC (Asao et al, 1998a). We found extended harvesting period in a closed nutrient flow system by grafting 'Shogoin-aonaga-fushinari' on 'Hokushin' or 'Aodai' (Asao et al, 1999b) and increased number of harvested fruits by adding AC in the nutrient solution .…”

“…Therefore, growth of these plants found to be inhibited by the released allelochemicals. So far several methods has been found to be effective in removing or degradating the phytotoxic substances released from plant roots during autotoxicity such as www.intechopen.com adsorption by activated charcoal (Asao et al, 1998a), degradation by microbial strain (Asao et al, 2004a) or auxin (2,4-D and NAA) supplementation , electrodegradation of root exudates (Asao et al, 2008) and TiO 2 photocatalysis (Sunada et al, 2008).…”

“…It was therefore felt necessary to examine the effects of root exudates on the growth of strawberry. Root exudates can be removed by adding activated charcoal (+AC) to the nutrient solution (Koda et al, 1977;Asao et al, 1998aAsao et al, , 1999cSato, 2004). In this study, we investigated the effects of non-renewal of the nutrient solution, and of adding AC on vegetative and reproductive growth of strawberry.…”