Interactions between abiotic factors and the bioactivity of biodynamic horn manure on the growth of garden cress (Lepidium sativum L.) in a bioassay

Alain Morau,Hans-Peter Piepho

doi:10.1186/s40538-020-0176-x

Abstract

BackgroundThe use of biostimulants like humic substances is a promising innovative approach in agriculture to activate and sustain physiological plant processes. The development of specific bioassays is required to study their bioactivity in laboratory conditions. In previous investigations, a soil-less bioassay with cress seedlings (Lepidium sativum L.) was developed for a biostimulant used in the biodynamic agriculture, the horn-manure preparation (HMP), a fermented cow manure sprayed at low concentrations onto fields. Objectives of the present study were to refine the bioassay by investigating the interactions between the HMP bioactivity and the test factors (i) water volume, (ii) gravistimulation, and (iii) exposure to fluorescent light.ResultsThe interactions between the test factors and the HMP treatment were significant in all series (p < 0.05, Wald F-test). Water overdose and gravitropic stress reduced root growth (down to − 24.2% and − 19.9%, respectively, p < 0.0001, Tukey–Kramer test). The HMP treatment partly compensated these effects by enhancing root growth by (i) water overdose (up to + 4.3%, p = 0.048, n = 4), and (ii) gravitropic stress (up to + 9.5%, p = 0.0004, n = 8). (iii) Furthermore, under the combined stress factors, fluorescent light exposure enhanced the HMP enhancing effect (up to + 12.3%, p = 0.007, n = 6).ConclusionsThe HMP bioactivity appeared to consist of a compensatory mode of action regarding the stress factors water overdose and gravistimulation, and a synergetic interaction with fluorescent light exposure. The HMP seems to interact with the plant sensory systems, likely stimulating the plant’s adaptability to its environment by increasing self-regulating processes. The bioassay sensitivity was successfully increased by integrating these interactions in the experimental set-up and adjusting the growth environment. This approach can be used to adjust the bioassay to other biostimulants.

Highlights

The use of biostimulants like humic substances is a promising innovative approach in agriculture to activate and sustain physiological plant processes
Interactions between the test factors and the biodynamic treatments In Series W and G, increase of laying time and water volume significantly reduced root growth. These plant reactions were presumably due to stress caused by gravistimulation and water overdose that adversely affected the availability of oxygen to the roots [9, 25]
The present results assessed the interactions between the horn-manure preparation (HMP) and the plant reactions to the three factors

Summary

Introduction

The use of biostimulants like humic substances is a promising innovative approach in agriculture to activate and sustain physiological plant processes. The development of specific bioassays is required to study their bioactivity in laboratory conditions. A soil-less bioassay with cress seedlings (Lepidium sativum L.) was developed for a biostimulant used in the biodynamic agriculture, the horn-manure preparation (HMP), a fermented cow manure sprayed at low concentrations onto fields. One promising approach is the use of biostimulants like humic substances (HS) to activate physiological plant processes [1,2,3,4]. The development of specific bioassays for biostimulants is of interest to assess their bioactivity in stress conditions

Methods

Results

Discussion

Conclusion