Biospeckle‐characterization of hairy root cultures using laser speckle photometry

Abstract

Monitoring is indispensable for the optimization and simulation of biotechnological processes. Hairy roots (hr, plant tissue cultures) are producers of valuable relevant secondary metabolites. The genetically stable cultures are characterized by a rapid filamentous growth, making monitoring difficult with standard methods. This article focuses on the application of laser speckle photometry (LSP) as an innovative, non‐invasive method to characterize Beta vulgaris (hr). LSP is based on the analysis of time‐resolved interference patterns. Speckle interference patterns of a biological object, known as biospeckles, are characterized by a dynamic behavior that is induced by physical and biological phenomena related to the object. Speckle contrast, a means of measuring the dynamic behavior of biospeckles, was used to assess the biospeckle activity. The biospeckle activity corresponds to processes modifying the object and correlates with the biomass growth. Furthermore, the stage of the cultures’ physiological development was assessed by speckle contrast due to the differentiation between active and low active behavior. This method is a new means of monitoring and evaluating the biomass growth of filamentous cultures in real time. As a potential tool to characterize hairy roots, LSP is non‐invasive, time‐saving, can be used online and stands out for its simple, low‐cost setup.

Monitoring the apical growth characteristics of hairy roots using non‐invasive laser speckle contrast imaging

“…Hairy roots of beetroot ( Beta vulgaris , B. vulgaris ) were used as a model organism as previously described in Schott et al., 2020 [ 31 ]. The cultures were induced by transformation with A. rhizogenes ATCC 15834 in line with the description by Pavlov et al., 2002 [ 65 ] and Weber et al., 2010 [ 69 ].…”

“…One potential approach for measuring plant tissue is laser speckle imaging [ 30 , 31 ]. Laser speckle imaging is an optical, non‐invasive method characterized by a simple experimental setup consisting of a laser source and a detector.…”

“…In previous speckle studies on hairy root networks, biospeckle activity was first shown to correlate with biomass growth [ 30 , 31 ]. In Chen et al., 2019 [ 30 ] and Schott et al., 2020 [ 31 ], biospeckle activity was defined as the sum of all areas of the imaged hairy root network that featured dynamic shifts in the speckle pattern.…”

“…Speckle contrast was then used to differentiate between areas of high and low dynamic changes. As a result, with increasing culture age, significantly higher activity was observed in the apical root regions, allowing initial interpretations of the physiological state of the overall culture [ 31 ]. The technical setup placed limits on any further differentiation and interpretation.…”

Label-free optical interferometric microscopy to characterize morphodynamics in living plants

“…(2018) ]. (C) Biospeckle activity of hairy roots after different cultivation times ( Schott et al., 2020 ). (D) Germination of a wheat seed.…”