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Cold radiofrequency plasma treatment modifies wettability and germination speed of plant seeds.

Bormashenko E, Grynyov R, Bormashenko Y, Drori E - Sci Rep (2012)

Bottom Line: We report the possibility to modify the wetting properties of the surfaces of a diversity of seeds including: lentils (Lens culinaris), beans (Phaseolus vulgaris) and wheat (Triticum, species C9) by cold radiofrequency air plasma treatment.Air plasma treatment leads to the dramatic decrease in the apparent contact angle.Significant growth of the peaks corresponding to the nitrogen containing groups in the mass spectra of air plasma treated seeds was registered by TOF-SIMS spectroscopy.

View Article: PubMed Central - PubMed

Affiliation: Ariel University Center of Samaria, Physics Faculty, Ariel, Israel. edward@ariel.ac.il

ABSTRACT
We report the possibility to modify the wetting properties of the surfaces of a diversity of seeds including: lentils (Lens culinaris), beans (Phaseolus vulgaris) and wheat (Triticum, species C9) by cold radiofrequency air plasma treatment. Air plasma treatment leads to the dramatic decrease in the apparent contact angle. Moreover, the speed of germination and yield (germination rate) of seeds can be modified by preliminary plasma treatment. The change in the wetting properties of seeds is at least partially due to oxidation of their surface under plasma treatment. Significant growth of the peaks corresponding to the nitrogen containing groups in the mass spectra of air plasma treated seeds was registered by TOF-SIMS spectroscopy.

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Water droplet deposited on untreated (a) and cold plasma treated (b) bean.
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f3: Water droplet deposited on untreated (a) and cold plasma treated (b) bean.

Mentions: Let us start from the examination of the surface of seeds. SEM images of the seeds and grains used in our investigation are depicted in Figure 1. It can be recognized that the surface of lentils and wheat grains is much rougher when compared with that of beans. The surface of lentils comprises granules with a characteristic size varying from 0.2 to 30 µm. It was supposed that these irregularly shaped, randomly distributed granules are built from proteins19. However, the surface of beans is rough also on a microscopic scale. Wetting of such microscopically-scaled rough surfaces is characterized by the so-called apparent contact angle defined as the angle between the tangent to the liquid-air interface and the apparent solid surface as macroscopically observed (the detailed topography of a rough surface cannot be viewed with regular optical means)2021. The wetting of miscroscopically rough random surfaces is an extremely complicated phenomenon. The apparent contact angle results from a complex interplay of chemical composition and roughness of the surfaces2021. It is agreed that the analysis of the wetting of rough inhomogeneous surfaces can be reduced to the Cassie and Wenzel models222324. We will not enter into details of the wetting regimes occurring on surfaces of lentil and bean seeds, but rather focus on the changes in these regimes caused by cold plasma treatment. The apparent contact angles were established as 127±2° and 98±2° for untreated lentils and beans correspondingly, as shown in Figures 2a, 3a, 4. The 15s cold air plasma irradiation of seeds decreased these angles to 20±1° and 53±1.5° for lentils and beans correspondingly (see Figures 2b, 3b). It should be stressed that this 15 s plasma treatment did not change the topography of the seed surfaces, a fact established with high resolution SEM and ESEM monitoring. The most pronounced change in the wettability was observed with plasma-treated wheat C9, when the apparent contact angle changed from 115±2° to zero, as shown in Figure 5. Thus, plasma treatment in this case caused a transition from partial to complete wetting. The variation of the time span of plasma treatment in the range of 15s – 2min did not influence the wetting of irradiated seeds.


Cold radiofrequency plasma treatment modifies wettability and germination speed of plant seeds.

Bormashenko E, Grynyov R, Bormashenko Y, Drori E - Sci Rep (2012)

Water droplet deposited on untreated (a) and cold plasma treated (b) bean.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3473364&req=5

f3: Water droplet deposited on untreated (a) and cold plasma treated (b) bean.
Mentions: Let us start from the examination of the surface of seeds. SEM images of the seeds and grains used in our investigation are depicted in Figure 1. It can be recognized that the surface of lentils and wheat grains is much rougher when compared with that of beans. The surface of lentils comprises granules with a characteristic size varying from 0.2 to 30 µm. It was supposed that these irregularly shaped, randomly distributed granules are built from proteins19. However, the surface of beans is rough also on a microscopic scale. Wetting of such microscopically-scaled rough surfaces is characterized by the so-called apparent contact angle defined as the angle between the tangent to the liquid-air interface and the apparent solid surface as macroscopically observed (the detailed topography of a rough surface cannot be viewed with regular optical means)2021. The wetting of miscroscopically rough random surfaces is an extremely complicated phenomenon. The apparent contact angle results from a complex interplay of chemical composition and roughness of the surfaces2021. It is agreed that the analysis of the wetting of rough inhomogeneous surfaces can be reduced to the Cassie and Wenzel models222324. We will not enter into details of the wetting regimes occurring on surfaces of lentil and bean seeds, but rather focus on the changes in these regimes caused by cold plasma treatment. The apparent contact angles were established as 127±2° and 98±2° for untreated lentils and beans correspondingly, as shown in Figures 2a, 3a, 4. The 15s cold air plasma irradiation of seeds decreased these angles to 20±1° and 53±1.5° for lentils and beans correspondingly (see Figures 2b, 3b). It should be stressed that this 15 s plasma treatment did not change the topography of the seed surfaces, a fact established with high resolution SEM and ESEM monitoring. The most pronounced change in the wettability was observed with plasma-treated wheat C9, when the apparent contact angle changed from 115±2° to zero, as shown in Figure 5. Thus, plasma treatment in this case caused a transition from partial to complete wetting. The variation of the time span of plasma treatment in the range of 15s – 2min did not influence the wetting of irradiated seeds.

Bottom Line: We report the possibility to modify the wetting properties of the surfaces of a diversity of seeds including: lentils (Lens culinaris), beans (Phaseolus vulgaris) and wheat (Triticum, species C9) by cold radiofrequency air plasma treatment.Air plasma treatment leads to the dramatic decrease in the apparent contact angle.Significant growth of the peaks corresponding to the nitrogen containing groups in the mass spectra of air plasma treated seeds was registered by TOF-SIMS spectroscopy.

View Article: PubMed Central - PubMed

Affiliation: Ariel University Center of Samaria, Physics Faculty, Ariel, Israel. edward@ariel.ac.il

ABSTRACT
We report the possibility to modify the wetting properties of the surfaces of a diversity of seeds including: lentils (Lens culinaris), beans (Phaseolus vulgaris) and wheat (Triticum, species C9) by cold radiofrequency air plasma treatment. Air plasma treatment leads to the dramatic decrease in the apparent contact angle. Moreover, the speed of germination and yield (germination rate) of seeds can be modified by preliminary plasma treatment. The change in the wetting properties of seeds is at least partially due to oxidation of their surface under plasma treatment. Significant growth of the peaks corresponding to the nitrogen containing groups in the mass spectra of air plasma treated seeds was registered by TOF-SIMS spectroscopy.

Show MeSH
Related in: MedlinePlus