Biological, Medical, and Agricultural Applications of Plasmas II

Non-thermal atmospheric-pressure plasma technologies have recently emerged as promising tools to enhance environmental resilience and sustainability in agriculture [1]. Using a dielectric barrier discharge (DBD) plasma, we have demonstrated that brief plasma irradiation (1–5 min) on seeds significantly improves germination, growth, and stress tolerance in various species, including Arabidopsis thaliana, rice, radish, and lettuce [2–10]. This chemical-free method is simple, rapid, and compatible with organic farming, offering a sustainable alternative to agrochemicals. Plasma triggers a cascade of molecular and physiological responses in plants. At the hormonal level, it reduces abscisic acid (ABA) and increases gibberellin (GA), promoting germination [8,9]. In leaves, plasma maintains elevated GA and enhances expression of photosynthesis-related proteins. Transcriptome analysis reveals downregulation of ABA biosynthetic genes and upregulation of ABA catabolic and α-amylase genes, supporting dormancy release and germination. Epigenetically, plasma alters DNA methylation: hypermethylation of the NCED5 promoter and hypomethylation of Amy1C and Amy3E promoters correlate with gene expression changes [11]. This suggests an epigenetic layer in plasma-induced phenotypes. Furthermore, mass spectrometry shows that plasma introduces quantifiable nitrate ions (NO₃⁻) into seeds [12]. These ions contribute to dormancy release and ABA metabolism via NLP8 binding to the CYP707A2 promoter. Plasma also modulates other hormone levels and antioxidant systems, enhancing tolerance to drought and salinity. Importantly, safety studies confirmed that rice grown from plasma-treated seeds caused no subacute toxicity in mammals [3]. As seed responses vary by physiological state, optimizing treatment parameters is essential [10]. Recently, new methods were developed to monitor immediate responses in plants such as Marchantia polymorpha after plasma exposure [13,14], bridging the gap between treatment and omics changes. Plasma agriculture integrates physics, plant biology, and sustainability, offering innovative strategies for adaptive food systems under climate stress.

Funding acknowledgement

This work was supported by JSPS KAKENHI JP22H04734, JP22H01212, JP20K05812, JP22K19160, JP22K03586, JP24H02246, JP24H02250, JST COI-NEXT JPMJPF2302, and JST PARKS JPMJSF2317.