Promotive or suppressive effects of ultrafine bubbles on crop growth depended on bubble concentration and crop species

Abstract

Previous research into the effects of ultrafine bubbles (UFB) on plant growth have been contradictory. To facilitate the resolution of these contradictions, the aim of the present study was to clarify the interspecific differences in growth responses among cereal/leguminous species under different levels of UFB concentrations. Seedlings of six species were grown hydroponically with three different UFB concentrations and two levels of plant nutrition to evaluate biomass and elongation growth. UFB growth promotion under zero-nutrition occurred in all species. Interspecific differences were noted in response to differing UFB concentration levels. Rice and soybean had higher above-ground biomass production at both low and high concentrations. Conversely, other crops exhibited promoted growth at only one of the concentrations. Negative effects occurred in full nutrient conditions except for root elongation. This study demonstrated that growth-promoting effects with UFB depended on the crop species being tested and the concentration of UFB used.