Salinity Stress Relief of Lettuce through Microbubbles Generated in Hydroponic Cultivation

Abstract

This study aimed to evaluate the effects of microbubbles on the growth of lettuce in hydroponic cultivation under high-salinity conditions. Lettuce (Lactuca sativa L. 'Cos lettuce') seeds were sown and then transplanted at 3 weeks after germination in a deep flow technique (DFT) hydroponic system. A 3% aqueous solution of NaCl was prepared to mimic the salinity of seawater. For microbubble treatment, 26 uniform seedlings were grown in two DFT systems, i.e., 13 seedlings in each system, and a microbubble generator was installed. A chiller and heater were installed on one side to maintain the water temperature. Microbubbles were generated throughout the experiment; the plants were grown for a total of 2 weeks, during which the pH, electrical conductivity (EC), and dissolved oxygen (DO) of the water did not change significantly compared to the control. Among the growth parameters, there were no differences in leaf length and width, but lettuce grown in the presence of microbubbles showed a significantly higher leaf number and longer root length. In addition, the shoot fresh weight and root fresh weight of the treated lettuce were 32.6% and 56% higher, respectively, than those grown in the control treatment. The dry weight of shoots and roots increased by 42% and 226%, respectively, in the microbubble treatment. These results suggest that microbubbles generated in the nutrient solution can increase the growth of salt-stressed plants in seawater-based hydroponic cultivation.

Nanobubble and Ozone Nanobubble Treatments Increase the Vase Life of Cut Cymbidium ‘Spring Pearl’

“…The germination rate of barley (Hordeum vulgare L. 'Hyegang') seeds treated with oxygen NBs was increased by approximately 40% compared to treatment with pure water (Oh et al, 2016). Increasing dissolved oxygen (DO) has the advantage of the removing residual pesticides and purifying contaminated water, which is required in agriculture (Noh et al, 2022). The water uptake of cucumber (Cucumis sativus L. cv.…”

“…NBs can be produced from various gases, such as oxygen, air, nitrogen, and carbon dioxide, which remain stable in liquids for a long time and replenish dissolved oxygen (DO) (Ahmed et al, 2018). Increasing DO is required in agriculture to purify water and promote plant and root growth (Noh et al, 2022). The root length of radish (Raphanus sativus L.) and wheat (Triticum aestivum) increased in plants treated with oxygen NBs (21.0 mg•L -1 DO) compared to the control (9.2 mg•L -1 DO) (Lee et al, 2021).…”