Towards Root Phenotyping in situ Using THz Imaging

by Luis Rivera and Nicholas Smith

 Introduction

    Root growth and development are critical for plant survival and productivity. While systems have been developed to automate the process of extracting root traits using 2D and 3D imaging under controlled conditions, to date, no systems exist that can non-destructively and repeatedly provide high-quality information on roots of field-grown plants. At the same time, Terahertz (THz) imaging is becoming a valuable tool in many areas, including medicine, pharmacology, security, etc. and has the potential for non-destructive, repeated imaging of root systems growing in pot and eventually field conditions. In this paper [1], we present a framework for investigating root growth and function of plants by analyzing and classifying THz data. The proposed system can successfully identify organic materials from potting soil or sand using both THz transmitted and reflected signals.

Proposed Method: This work relies on the HiGUSSS method developed in [2].

Experiments and Results: Samples including carrots, sweet potatoes, turnip, rocks and wood pieces were buried in sand and in potting soil and imaged using both transmission and reflection signals. This allowed us to compare the two imaging methods in order to determine their effectiveness at acquiring the shape and size of different buried organic materials.

(a)      (b)

(c)      (d)

Figure 1. (a) Photo of the samples used for the THz reflection test including a sweet potato, a turnip, four rocks and a piece of tree branch (uncovered to show the objects); (b) The time domain reflected signal at a particular point in (c); (c) Time domain THz reflection image of the objects after being completely buried by dry sand; (d) Final classification using the HiGUSSS Framework.

Table 1. Classification accuracy for the THz Transmission experiments.

Table 2. Classification accuracy for the THz Reflection experiments.

Conclusion: The results presented in this work demonstrate the potential of THz imaging to detect and identify the different objects buried in sand and potting soil. This system is the first step towards revolutionizing root phenotyping in situ, and thus genetic improvement on the basis of root characteristics.

    References

1. N. R. Smith, L. A. Rivera, N. Burford, T. Bowman, M. O. El-Shenawee, and G. N. DeSouza, “Towards Root Phenotyping in situ Using THz Imaging”, 40th IEEE International Conference on Infrared, Millimeter, and Terahertz Waves, Hong Kong, August 23 - 28, 2015.

2. L. A. Rivera, N. R. Smith, and G. N. DeSouza, “High-Accuracy Recognition of Muscle Activation Patterns Using a Hierarchical Classifier”, 5th IEEE RAS & EMBS International Conference on Biomedical Robotics and Biomechatronics, São Paulo, Brazil, August 12 – 15, 2014.