In vivo characterisation of field pea stem wall thickness using optical coherence tomography

Qi Fang; Felipe A Castro-Urrea; Felix Haederle; Rowan W Sanderson; Dilusha Silva; Wallace A Cowling; Brendan F Kennedy

doi:10.1186/s13007-023-01075-1

In vivo characterisation of field pea stem wall thickness using optical coherence tomography

Plant Methods. 2023 Oct 11;19(1):105. doi: 10.1186/s13007-023-01075-1.

Authors

Qi Fang^{1

2}, Felipe A Castro-Urrea^{3

4}, Felix Haederle⁵, Rowan W Sanderson^{5

6}, Dilusha Silva^{5

3}, Wallace A Cowling^{3

4}, Brendan F Kennedy^{5

6

7

8}

Affiliations

¹ Department of Electrical, Electronic & Computer Engineering, School of Engineering, The University of Western Australia, Crawley, WA, 6009, Australia. qi.fang@uwa.edu.au.
² Centre for Medical Research, BRITElab, Harry Perkins Institute of Medical Research, QEII Medical Centre, The University of Western Australia, Crawley, WA, 6009, Australia. qi.fang@uwa.edu.au.
³ The UWA Institute of Agriculture, The University of Western Australia, Crawley, WA, 6009, Australia.
⁴ School of Agriculture and Environment, The University of Western Australia, Crawley, WA, 6009, Australia.
⁵ Department of Electrical, Electronic & Computer Engineering, School of Engineering, The University of Western Australia, Crawley, WA, 6009, Australia.
⁶ Centre for Medical Research, BRITElab, Harry Perkins Institute of Medical Research, QEII Medical Centre, The University of Western Australia, Crawley, WA, 6009, Australia.
⁷ Australian Research Council Centre for Personalised Therapeutics Technologies, Melbourne, VIC, Australia.
⁸ Institute of Physics, Nicolaus Copernicus University, Torun, Poland.

Abstract

Background: Modern field pea breeding faces a significant challenge in selecting lines with strong stems that resist lodging. Traditional methods of assessing stem strength involve destructive mechanical tests on mature stems after natural senescence, such as measuring stem flexion, stem buckling or the thickness of dry stems when compressed, but these measurements may not correspond to the strength of stems in the living plant. Optical coherence tomography (OCT) can be used as a noncontact and nondestructive method to measure stem wall thickness in living plants by acquiring two- or three-dimensional images of living plant tissue.

Results: In this proof-of-principle study, we demonstrated in vivo characterisation of stem wall thickness using OCT, with the measurement corrected for the refractive index of the stem tissue. This in vivo characterisation was achieved through real-time imaging of stems, with an acquisition rate of 13 milliseconds per two-dimensional, cross-sectional OCT image. We also acquired OCT images of excised stems and compared the accuracy of in vivo OCT measurements of stem wall thickness with ex vivo results for 10 plants each of two field pea cultivars, Dunwa and Kaspa. In vivo OCT measurements of stem wall thickness have an average percent error of - 3.1% when compared with ex vivo measurements. Additionally, we performed in vivo measurements of both stem wall thickness and stem width at various internode positions on the two cultivars. The results revealed that Dunwa had a uniform stem wall thickness across different internode positions, while Kaspa had a significantly negative slope of [Formula: see text]0.0198 mm/node. Both cultivars exhibited an increase in stem width along the internode positions; however, Dunwa had a rate of increase of 0.1844 mm/node, which is three times higher than that of Kaspa.

Conclusions: Our study has demonstrated the efficacy of OCT for accurate measurement of the stem wall thickness of live field pea. Moreover, OCT shows that the trends of stem wall thickness and stem width along the internode positions are different for the two cultivars, Dunwa and Kaspa, potentially hinting at differences in their stem strength. This rapid, in vivo imaging method provides a useful tool for characterising physical traits critical in breeding cultivars that are resistant to lodging.

Keywords: Field pea; In vivo measurement; Optical coherence tomography; Stem structure; Stem wall thickness.