The trigger for germination requires a number of external parameters to be met, which will vary from seed to seed, but are generally a combination of water, temperature and light. It is then provided with stored foods through the endosperm during germination, a process which is the transition from an inactive to active seed that grows, ruptures the seed coat and develops from a seedling first into a plantlet, which is generally still frail and particularly sensitive to external stresses, to then a more stress-resistant autotrophic plant. Inside the dry mature seed, the embryo is in a partially desiccated, quiescent state, poised to germinate upon the addition of water or in other words, imbibition. The living tissues of seeds are protected by the seed coat (testa), which can vary between species and cultivars, or depend on the plants being fertile or clones unable to produce the next generation. Seed Structure and DevelopmentĪlthough very diverse, all seeds have generally evolved to contain all their needs to develop into plantlets once the environmental conditions are perceived as appropriate. In section Non-thermal Plasma (NTP) as a Seed Processing Technology, plasma will be introduced and the motivation for its application on seeds followed by a corroboration of recent research to provide an overview of physical, chemical, and biological mechanisms that can be triggered by plasma components is in section Mechanisms of How Non-thermal Plasma Affects Seeds and Their Subsequent Development. The Seed Structure and Development section will be presented first to establish a common ground, followed by a summary of current techniques used to improve seed survival in section Seed Performance.
Considering that plasma agriculture has been gaining more attention recently, it is therefore useful to have a review dedicated to seeds, which is understandable to an interdisciplinary audience of biologists and plasma physicists. The aim of this review is to centralize the hypotheses and present the evidence to date of how plasma treatments affect seeds, considering that there is difficulty in standardizing the methodology in this interdisciplinary field given the plethora of variables in the experimental setup of the plasma device and handling of biological samples. The world population is projected to increase to 10 billion by 2050 and even without increasing the food supply, it is necessary to maintain the current food production and quality.
The motivation driving plasma-seed treatment research is the importance of food. Instead, a summary of the mechanisms of how plasma may be affecting the seed and its germination and developmental properties will be provided and discussed. This review intentionally does not include seed disinfection and sterilization due to already existing reviews. Furthermore, seedlings seem to be too sensitive to the oxidation of plasma and therefore, seeds seem to be the ideal target. Seeds are the first step of the agricultural cycle and at this stage, the plant can be given the highest probability of establishment, despite environmental conditions, to exploit the genetic potential of the seed.
The ever increasing interest for plasma agriculture drives the need for a review dedicated to seeds, which is understandable to an interdisciplinary audience of biologists and plasma physicists. The aim of this review is to summarize the hypotheses and present the evidence to date of how plasma treatments affect seeds, considering that there is difficulty in standardizing the methodology in this interdisciplinary field given the plethora of variables in the experimental setup of the plasma device and handling of biological samples. Plasma treatments are currently being assessed as a seed processing technology for agricultural purposes where seeds are typically subjected to pre-sowing treatments to improve the likelihood of timely and uniform germination. Swiss Plasma Center, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.Alexandra Waskow *, Alan Howling and Ivo Furno
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