# Experimental Investigation into the Influence of Plasma Technology on Seed Surface Wettability
## 1 Introduction  
Climate change has a significant impact on the overall productivity of food. Differences are mainly represented by a lack of water. Nearly 70% of the world's water is already used for agriculture [1]. Water is vital for plant growth, development, and productivity. Water stress causes limitations for plant growth and performance of cultivated crops more than any other environmental factor [2]. The water absorption of seeds is crucial for the initiation of swelling and germination. At the same time, water intake plays a decisive role in seed emergence [3]. Greater water intake is crucial in stressful conditions, such as drought or high temperature [4]. Stressful situations require some support for plant growththrough proper treatment, such as chemical, biological, or physical treatment. Recent physical procedures involve the use of low-temperature plasma discharge. This technology has recently found application in plant biology and agriculture [5].  
Plasma discharges are now widely used in many industries in processes such as surface sterilisation [6; 7], biomedical applications [8], object decontamination in closed containers [9], inactivation of bacteria [10] and removal of contaminants from water [11; 12]. Plasma can change the surface properties of the seed in terms of surface tension and nutrient [13] and water permeability through its layers into the interior. Water absorption is related to changes in seed surface and structure. These changes can be indicated by determining the surface's wettability by measuring the contact angle [14]. A more wettable surface in the sense of reducing contact angle and higher surface tension has a beneficial effect on water intake and more effective adhesion of possible biological treatment.  
There have been several previously published articles in which the effect of plasma treatment on the surface changes is presented, for example in [15; 16; 17; 18; 19; 20]. [PERSON] et al. used DBD plasma discharge as a pre-germination treatment for _Leucareu_ seeds to improve wettability and germination [15]. [PERSON] et al. observed the effect of DBD-type discharge on _Erythrina velutina_ seeds in which the contact angle was reduced [16]. [PERSON] et al. used the same type of discharge to reduce the contact angle in seeds of _Mimosa Caeslpiniafolia_[17]. [PERSON] et al. improved the wetting angle in mung bean seeds with the help of RF type discharge [18]. [PERSON] et al. used a similar type of discharge and observed a lower contact angle in wheat seeds [19]. [PERSON] et al. discovered a positive effect of diffuse coplanar discharge on the wettability of maize, barley, and wheat seeds [20]. Unfortunately, their results are complicated to compare because of the vast complexity of plasma systems with many different process parameters and the diverse seed type used.  
As reported in [21], conventional seed treatment methods can lead to a number of negative effects, including significant reductions in germination, dry shoot biomass and reduced plant vigour. For this reason, the present study investigates the use of low temperature plasma as an alternative ecological method for seed treatment, with the ambition of eliminating the above mentioned disadvantages of conventional methods. Hence, this paper aims to compare two different plasma discharges concerning the various seed wettability. Since each plasma system is unique and complex, the processing parameters of the devices were considered. Low-pressure microwave discharge (LPMD) and atmospheric pressure discharge (APD), respectively, were used for experiments concerning three representatives of diverse seed types such as cereal, oilseed, and legume.