Growth response of hydroponic leaf lettuce and komatsuna to ozone microbubble treatment

Abstract

Previously, we found that ozone microbubble (O₃MB) treatments of 0.2 mg L⁻¹ of dissolved ozone (DO₃) are effective for sterilizing hydroponic solutions. However, there are few studies on cultivated plant growth responses to O₃MB-treated hydroponic solutions. We investigated effects of different O₃MB treatments in hydroponic solutions on the growth of leaf lettuce and komatsuna plants, and inhibiting factors for komatsuna growth. Fe concentrations in O₃MB-treated hydroponic solutions decreased significantly compared with control solutions because of the precipitation of oxidized Fe. The growth of hydroponic lettuce treated with O₃MB was equivalent to that of the control. However, the growth of komatsuna was suppressed with increasing DO₃ concentrations. Leaf lettuce might avoid Fe deficiency by secreting riboflavin from roots. On the other hand, since komatsuna does not secrete riboflavin against Fe deficiency, Fe deficiency in hydroponic solutions might lead to growth suppression. We investigated the influence of added Fe in hydroponic solutions treated with O₃MB on the growth of komatsuna. No growth differences for komatsuna were observed between Fe-added hydroponic solutions treated with O₃MB and the control solution. Growth suppression of O₃MB-treated hydroponic komatsuna may be avoidable by Fe addition.

Keywords:

• Fe
• hydroponic solutions
• komatsuna
• leaf lettuce
• Mn
• ozone microbubbles