Noninvasive diagnosis of seed viability using infrared thermography

Abstract

Recent advances in the noninvasive analyses of plant metabolism include stress imaging techniques, mainly developed for vegetative tissues. We explored if infrared thermography can be used to predict whether a quiescent seed will germinate or die upon water uptake. Thermal profiles of viable, aged, and dead Pisum sativum seeds were recorded, and image analysis of 22,000 images per individual seed showed that infrared thermography can detect imbibition-and germination-associated biophysical and biochemical changes. These "thermal fingerprints" vary with viability in this species and in Triticum aestivum and Brassica napus seeds. Thermogenesis of the small individual B. napus seeds was at the limit of the technology. We developed a computer model of "virtual pea seeds," that uses Monte Carlo simulation, based on the heat production of major seed storage compounds to unravel physico-chemical processes of thermogenesis. The simulation suggests that the cooling that dominates the early thermal profiles results from the dissolution of low molecular-weight carbohydrates. Moreover, the kinetics of the production of such "cooling" compounds over the following 100 h is dependent on seed viability. We also developed a deterministic tool that predicts in the first 3 hours of water uptake, when seeds can be redried and stored again, whether or not a pea seed will germinate. We believe that the early separation of individual, ungerminated seeds (live, aged, or dead) before destructive germination assessment creates unique opportunities for integrative studies on cell death, differentiation, and development.aging | crop | germination | imaging | stress S eeds are attractive experimental model systems to study general biological phenomena, such as aging, cell death, and development. Desiccation tolerant "orthodox" seeds can be stored long term in the dry state, but lethal damage can be induced rapidly by "artificial aging," involving the elevation of seed moisture content (MC) and temperature (1). However, the biochemical and molecular interpretation of aging is hindered by the use of inseparable populations of viable and nonviable seeds, in which the partitioning of analytes in seeds of differential quality is unknown. Seed-quality studies would benefit from a tool that identifies individual viable and nonviable seeds before use. Moreover, global agriculture is fundamentally dependent on the production, distribution, and germination of high-quality seeds.Pioneering studies (2-7) using microcalorimetry (8, 9) demonstrated that metabolic heat flows can be used to assess gross metabolism associated with germination processes. However, microcalorimeters do not capture thermal activity in the first phase of seed imbibition while samples equilibrate in the instrument. In addition, they are closed systems, preventing dissipation of heat and gas, with potential confounding feedback on seed metabolism. Consequently, these microcalorimetric studies were inconclusive as to whether temperature rises or falls during the initial stages of s...

Feasibility of near infrared spectroscopy for analyzing corn kernel damage and viability of soybean and corn kernels

“…Some researchers have analyzed the germination process as an attempt to determine in advance which seeds produce either abnormal plants or are dead seeds. Nondestructive studies of changes in temperature profile during seed aging helped in the prediction of seed viability by Infrared thermography (Kranner et al, 2010). By repetitive comparison of the thermal profile of a given seed with previously studied seed profiles, dead seeds were discriminated from live seeds at 85% accuracy, and heat-killed seeds from viable seeds at 100%.…”

Application of Thermal Imaging in Agriculture and Forestry

“…Thermal profile of seeds can be used to detect subtle changes in temperature (Kranner et al, 2010). Classification and separation of seeds using the remote sensing technique has been reported by Zhang et al (2012).…”

Evaluation of 3D/2D Imaging and Image Processing Techniques for the Monitoring of Seed Imbibition

“…As visible in Figure 3F, the temperature profile varies according to the various stages of the imbibition process, starting with a step of temperature increase (from less than 1 h to several hours), then followed by a sharp temperature decrease. Tested in significant amounts on imbibed seeds in [31], these changes in temperature profile may be used to reliably detect and predict the capability of seeds in the first hours for imbibition, as such thermal variations may be related to biochemical changes and transformation of the seed reserves before germination.…”

“…Thermography is a 2D non-invasive technique that can detect and characterize imbibition associated with biophysical and biochemical changes as described in [31,33], via temperature profiles as illustrated in Figure 3F. Access to such profiles constitutes a characteristic indicator of the seed imbibition, which may vary depending on the species and environmental conditions of this imbibition process.…”

“…The early stages of plant development at the scale of seeds and seedlings can also be analyzed using thermography. It has recently been used to evaluate the germination capacity of legume seeds [30], to detect biophysical and biochemical changes during imbibition and germination correlated to viability [31] and to discriminate hypocotyl and radicle of seedlings during the elongation stage due to significant thermal differences [32,33].…”