Identification of ROS Produced by Nanobubbles and Their Positive and Negative Effects on Vegetable Seed Germination

Abstract

Exogenous reactive oxygen species (ROS) produced by nanobubble (NB) water offer a reasonable explanation for NBs' physiological promotion and oxidation effects. To develop and exploit the NB technology, we have performed further research to identify the specific ROS produced by NBs. Using a fluorescent reagent APF, a Fenton reaction, a dismutation reaction of superoxide dismutase and DMSO, we distinguished four types of ROS (superoxide anion radical (O·), hydrogen peroxide (HO), hydroxyl radical (·OH), and singlet oxygen (O)). ·OH was confirmed to be the specific ROS produced by NB water. The role of ·OH produced by NB water in physiological processes depends on its concentration. The amount of exogenous ·OH has a positive correlation with the NB number density in the water. Here, spinach and carrot seed germination tests were repeatedly performed with three seed groups submerged in distilled water, high-number density NB water, and low-number density NB water under similar dissolved oxygen concentrations. The final germination rates of spinach seeds in distilled water, low-number density NB water, and high-number density NB water were 54%, 65%, and 69%, respectively. NBs can also promote sprout growth. The sprout lengths of spinach seeds dipped in NB water were longer than those in the distilled water. For carrot seeds, the amount of exogenous ·OH in high-number density NB water was beyond their toxic threshold, and negative effects were shown on hypocotyl elongation and chlorophyll formation. The presented results allow us to obtain a deeper understanding of the physiological promotion effects of NBs.

Nanopriming technology for enhancing germination and starch metabolism of aged rice seeds using phytosynthesized silver nanoparticles

“…As plant cell walls determine shape and the rate and direction of growth of individual cells as well as the mechanical resistance of whole tissues, the loosening of cell walls is an important process in all stages of plant development, requiring elongation growth or tissue weakening 77 . It has been approved that ROS, including •OH can act as a key component in cell wall loosening, testa and endosperm weakening, which is essential for radicle protrusion in seed germination 77 – 79 . As observed by ESR technique, AgNPs could mediate the generation of •OH, and thus act as ROS-generating agent.…”

Plasma physics of liquids—A focused review

“…Yet, the likelihood of this hypothesis is underlined by several indications found in literature. For instance, aqueous nanobubble solutions produce hydroxyl radicals, 354,355 which makes them interesting for water treatment (see Refs. 190 and 192 for two reviews) and agricultural applications.…”

“…Indeed, experimental studies have shown the growth promotion of plants, fish, and mice by nanobubbles. [354][355][356] Both applications are reminiscent of the observed effects induced by plasma treated solutions. 357,358 Figure 27, for instance, draws an analogy between the favorable long-term effect of plasma treated water and nanobubble solution as fertilizer on the growth of plants.…”

Pre-treatment Technologies to Enhance Anaerobic Digestion

“…Palladium electrode with ultrasonication has been used to form nanobubbles of 300-500 nm diameter [23]. Nanobubbles form reactive free radicals as they collapse due to the presence of ions in groups at the gas-liquid interface [24]. The ability of nanobubbles to form reactive free radicals makes them potent applicants in the field of pre-treatment of wastewater components.…”