The Modulatory Effects of Non-Thermal Plasma on Seed’s Morphology, Germination and Genetics—A Review

Abstract

Non-thermal plasma (NTP) is a novel and promising technique in the agricultural field that has the potential to improve vegetal material by modulating the expression of various genes involved in seed germination, plant immune response to abiotic stress, resistance to pathogens, and growth. Seeds are most frequently treated, in order to improve their ability to growth and evolve, but the whole plant can also be treated for a fast adaptive response to stress factors (heat, cold, pathogens). This review focuses mainly on the application of NTP on seeds. Non-thermal plasma treated seeds present both external and internal changes. The external ones include the alterations of seed coat to improve hydrophilicity and the internal ones refer to interfere with cellular processes that are later visible in metabolic and plant biology modifications. The usage of plasma aims to decrease the usage of fertilizers and pesticides in order to reduce the negative impact on natural ecosystem and to reduce the costs of production.

Positive Effect Induced by Plasma Treatment of Seeds on the Agricultural Performance of Sunflower

“…The effect of wettability increase cannot be excluded, but much more complex action mechanisms of the plasma are discussed in the literature, including modifications in the content and balance of phytohormones, effects on gene expression, activation of the energy metabolism, etc. [ 4 , 5 , 10 , 11 ], which are not entirely understood and should represent the subject of further research.…”

“…Controlled delivery of plasma-generated species, adapted to plant needs at different development stages, is considered to be the key strategy for successful application of plasma in the agriculture field. The prospect of using plasma to stimulate the expression of various genes related to embryonic development, plant growth, resistance to pathogens and tolerance to abiotic stress is emphasized in the review of Leti et al [ 4 ]. Novel findings evidencing changes induced by NTP treatment of seeds at the molecular level are analyzed in detail by Mildaziene et al [ 5 ].…”

Germination and First Stages of Growth in Drought, Salinity, and Cold Stress Conditions of Plasma-Treated Barley Seeds

“…The results reported here for barley plants are in line with recent studies with other plants proving that plasma gives rise to biochemical modifications. These have been attributed to the activation of certain enzymes, the modification of proteins, or the activation of specific growth and gene expression factors. – A common hypothesis in these works on barley and other plants is that ROS and RNS plasma species formed on the surface of seeds may diffuse into their interior and affect key molecular mechanisms , involving enzymes, proteins, and other biochemical markers (for a comprehensive account of these recent investigations, see the contribution of recent papers to the topic – ,– ). In a recent work from our group on barley seeds, we have shown that plasma affects the ABA (abscisic acid) growing factor in a similar way to hydrogen peroxide, both treatments leading to an increase in germination rates thanks to the enhanced ROS content .…”

“…During the last years, among the large variety of methods utilized to improve seedling and plant growth, the application of low-temperature plasmas has received considerable attention in the scientific literature. – Recent reviews on the subject have highlighted the complexity of the biochemical and gene expression effects that can be triggered when treating seeds with plasmas. Also, the diversity of scenarios and variables that must be considered in these studies, including type of plants, characteristics of cold plasmas, or environmental growth conditions. – …”

“…Plasmas have been also applied to improve the water absorption capacity of seeds, avoiding seed dormancy effects and seed borne diseases and increasing seed resistance toward abiotic stresses . In this regard, very often, the improvements in germination rate – , and plant growth have been linked to an increase in seeds’ water uptake capacity upon their exposure to plasmas. ,,– It has been also highlighted that plasma generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) (in general RONS) affects the biochemistry, the enzymatic activity, or even the gene expression processes of seeds and plants. – ,– However, the role of ROS or RNS and even their chemical nature is not yet completely clarified or understood, mainly because their short lifetimes make their detection difficult . Peroxo- and superoxide-like, H 2 O 2 , and NO x species have been claimed as possible chemical species, which formed on the surface of plasma-treated seeds and then diffused to their interior, contributing to trigger a series of biochemical and gene regulation processes crucial for the germination and the development of plants.…”