Plant biostimulants and their effects on symbiotic microorganisms

One of the great ecologic challenges of the 21st century is the reduction of negative environmental impacts of agriculture. A frequently overlooked aspect is the negative impact of agrotechnical interventions such as intensive chemical treatments on key ecophysiological features of plants, symbiosis with mycorrhizal fungi and endophytic microorganisms. The use of environmentally friendly plant biostimulant products can be a solution for new sustainable crop production systems.

Plant biostimulants
Biostimulants are biologically active substances derived from natural or waste materials. They can promote plant growth and/or enhance plant defense against various stress factors. The peculiarity of biostimulants is that they do not contain a high percentage of active substances, so they cannot be considered as typical fertilizers or as plant protection agents. Typically, the active ingredients of biostimulants affect plant metabolism and trigger processes in the plant that generally improve its growth and health. Interestingly, for most biostimulants the exact mechanism of action is not yet known, which opens up many possibilities for scientific research.

Feather protein hydrolyzate
In the EU project BIOSTISYM, funded under “Marie Skłodowska-Curie” program, researchers at the Institute of Botany have investigated the biostimulating effects of feather protein hydrolyzate, provided by the Institute of Chemical Process Fundamentals (Bioraf – Biorefinery Research Centre of Competence[1]), on wheat and its interaction with symbiotic microorganisms.

Feather is a waste material of poultry processing and is annually accumulated in the order of billions of tons. Feather waste disposal is particularly problematic because feathers are generally landfilled or burnt causing environmental pollution[2]. Such processing leaves valuable feather compounds untapped.  Feathers contain more than 90% of proteins[3] that could be converted to peptides and amino acids, for example, via pressure hydrolysis[4], which is in compliance with animal by-products EU regulation[5]. Applied to plants, these compounds may enhance protein synthesis, stress resistance, photosynthesis, stomata function, chelating effect, fruit formation, and increase the content of amino acids and phytohormones. Moreover, the re-use of raw materials that are disposed of as waste is one of the key principles of the Circular Economy Package adopted by the EC in 2015[6]. The EC proposed a Regulation to boost the use of organic and waste-based fertilizers bringing them on a level playing field with traditional, non-organic fertilizers. Currently, only 5% of waste organic material is recycled and used as fertilizers, but the recycled bio-waste could substitute up to 30% of inorganic fertilizers6.

 

Biostimulating effects of protein hydrolyzate on wheat and its interaction with symbiotic microorganisms
A two-year project, BIOSTISYM, focused on winter wheat, as high doses of agrochemicals are commonly applied during the cultivation of this important crop. The use of biostimulants could partially reduce the need for these chemicals to be applied to the crop while maintaining a healthy soil ecosystem.

First, the biostimulating effect of the protein hydrolyzate was verified by the scientists in the greenhouse pot experiment. The hydrolyzate has shown a positive effect on plant growth depending on phosphorus nutrition. In addition, there was no negative effect on the colonization of wheat roots by mycorrhizal fungi.

For field crops such as wheat, it is necessary to demonstrate the efficacy of agricultural products under field conditions. In the field trial, it was shown that the hydrolyzate applied at the beginning of the stem elongation stage increased the yield of almost a 5% in comparison with the control plants not treated with the hydrolyzate. In addition, two weeks after the application of protein hydrolyzate, the amount of aboveground biomass, plant height and chlorophyll content of the leaves increased significantly. Scientists suppose that influencing these plant growth parameters at an early developmental stage is related to yield increases. Also under field conditions, the colonization of wheat roots with mycorrhizal fungi was not negatively affected by the application of hydrolyzate. The application of hydrolyzate positively affected the number of vesicles, the storage organs of the arbuscular mycorrhizal fungi. There is a hypothesis that the application of a protein hydrolyzate to the plant may indirectly affect the composition of microbial communities on plant roots. However, the exact mechanism of affecting arbuscular mycorrhizal fungi has not yet been elucidated.

Feather protein hydrolyzate, thanks to its biostimulating effects on wheat, appears to be a promising supplement to the cultivation technology, where it could amend or partially replace traditional fertilizers and thereby reduce the environmental burden of chemicals. This is due to the fact that this biostimulant does not affect negatively symbiotic microorganisms and is also applicable to organic cultivation. However, for the successful introduction of the hydrolyzate into agricultural practice, it is first necessary to re-verify the effectiveness under field conditions and ensure a stable composition of the biostimulating product.

Other BIOSTISYM  activities
Under the BIOSTISYM project, the researchers aimed at increase of public awareness of sustainable agriculture and the influence of plant interactions with beneficial microorganisms through agro-technical interventions. Educational lectures were organized as part of the program “Do not be afraid of science” organized by the Academy of Sciences of the Czech Republic (AS CR) for students of secondary schools, student internships within the “Open Science” program of the AS CR, and contributions for Science Week and Science Festival, popularizing events of the AS CR. The results of the project were presented at three international conferences and two scientific papers will be published in peer-reviewed journals. The project was also presented in the exhibition premises of the Průhonice Castle.

Project presentation at the international conferences

9th International Conference                           Plant Biology Europe                     Microbiomes underpinning Agriculture
on Mycorrhiza Praha,                                      Copenhagen,                                 Cork,
30. 7. – 4. 8. 2017                                           18. – 21. 6. 2018                           1. – 2.10. 2018

Project presentation in the premises of the Institute of Botany

Contact: Eva Baldassarre Švecová, eva.svecova@ibot.cas.cz

 

[1]Centrum kompetence pro výzkum biorafinací, https://bioraf.cz/.

[2] Vasileva-Tonkova, E., Gousterova, A. and Neshev, G., 2009. Ecologically safe method for improved feather Wastes Biodegradation. Intern. Biodeterior. Biodegrad., 63, 1008-1012.

[3] Tiwary and Gupta, 2012. Rapid Conversion of Chicken Feather to Feather Meal (PDF, 2,6 MB)Using Dimeric Keratinase from Bacillus licheniformis ER-15. J Bioproces Biotechniq, 2:4.

[4] Hanika, J., Šolcová, O., Kaštánek, P., 2015. Pressure Hydrolysis of Protein in Waste of Chicken Cartilage and Feathers in the Presence of Carbon Dioxide. http://www.nusl.cz/ntk/nusl-189274 [25-3-2019].

[5]REGULATION (EC) No 1069/2009 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL, 2009.

[6]European Commission – Press release. Circular economy: New Regulation to boost the use of organic and waste-based fertilisers, Brussels, 17 March 2016. http://europa.eu/rapid/press-release_IP-16-827_en.htm [25-3-2019].