Observations of Ice Nucleation and Propagation in Plants Using Infrared Video Thermography

Abstract

We evaluated the use of infrared (IR) video thermography to observe directly ice nucleation and propagation i n plants. An imaging radiometer with an HgCdTe long-wave (8-12 pm) detector was utilized to image the thermal response of plants during freezing. IR images were analyzed in real time and recorded on videotape. lnformation on the videotape was subsequently accessed and analyzed utilizing IR image analysis software. Freezing of water droplets as small as 0.5 pL was clearly detectable with the radiometer. Additionally, a comparison of temperature tracking data collected by the radiometer with data collected with thermocouples showed close correspondence. Monitoring of an array of plant species under different freezing conditions revealed that ice nucleation and propagation are readily observable by thermal imaging. I n many instances, the ice nucleation-active bacterium Pseudomonas syringae placed on test plants could be seen to initiate freezing of the whole plant. Apparent ice nucleation by intrinsic nucleators, despite the presence of ice nucleation-active bacteria, was also evident in some species. Floral bud tissues of peach (Prunus persica) could be seen to supercool below the temperature of stem tissues, and ice nucleation at the site of insertion of the thermocouple was frequently observed. Rates of propagation of ice i n different tissues were also easily measured by thermal imaging. This study demonstrates that I R thermography is an excellent method for studying ice nucleation and propagation in plants. ~~ ~Frost-sensitive plant species have limited ability to tolerate ice formation in their tissues (Cary and Mayland, 1970;Burke et al., 1976). Although not damaged by cold temperatures alone, these species exhibit freeze damage when ice formation occurs. The control of frost injury to such species is achieved by avoiding ice formation. One way to do this is to warm the plant to temperatures above the freezing point of the tissue. Alternatively, plants can supercool to some extent below 0°C and avoid damaging ice formation (Lucas, 1954;Modlibowska, 1962;Cary and Mayland, 1970;Burke et al., 1976;Lindow et al., 1978; Single, 1976, 1979;Proebsting et al., 1982;Ashworth and Kieft, 1995;Lindow, 1995). The temperature Video sequences of the experiments documented in this study are available for educationai purposes in NTSC or PAL format by sending a blank tape and cover letter (specifying NTSC or PAL format) to the corresponding author.* Corresponding author; e-mail mwisniew@asrr.arsusda.gov; fax 1-304-728-2340.to which plants can supercool varies in plant species and is influenced by the presence of ice-nucleating agents that may be of plant (Ashworth and Davis, 1984;Anderson and Ashworth, 1985; Andrews et al., 1986;Gross et al., 1988) or bacterial (King et al., 1954;Kaku, 1964;Lindow et al., 1978Lindow et al., , 1982Lindow, 1982Lindow, , 1983Lindow, , 1985Lindow, , 1995Gross et al., 1984;Hirano et al., 1985) origin. Although the abundance of ice nuclei on plants can be estimated by freezing droplets of...

Advances in physiological and molecular aspects of plant cold tolerance

“…Pseudomonas syringae) can stimulate ice nucleation these have been used in freezing experiments to aid ice formation during infrared observation experiments (Wisniewski et al 1997; Wisniewski 1998; Pearce & Fuller 2001). Typically, plants, which were treated with droplets of INA bacteria began to freeze first compared with samples or plants treated with water droplets only.…”

“…Computer software has also been used to analyze recordings of infrared video tape to study all stages of ice formation and to quantify the magnitude of the exotherms observed and their duration (Al-Swedi et al 2013). Furthermore, the speed of ice front travel can also be determined by determining the start and the end times of the whole tissue being frozen and barriers to ice spread being detected (Wisniewski et al 1997;Pearce & Fuller 2001) (Figure 4).…”

“…The determination of the exact location of initial ice formation (point of ice nucleation) and how it progresses throughout the plant (ice spread) is very important information that needs to be known prior to devising methods to protect plants. Wisniewski et al (1997) were among the first to use infrared thermal imaging technology to determine where ice first begins to form in a plant and at what temperature, based on the principle of release of heat when ice is formed (exotherm which is the process that describes the chemical reaction when energy is released usually in the form of heat). By using infrared video thermography, these researchers observed a plant freezing and followed the progress of ice formation throughout the plant.…”

“…By using infrared video thermography, these researchers observed a plant freezing and followed the progress of ice formation throughout the plant. Subsequently, ice formation has been tracked by using an infrared camera system in many species including apple (Malus ssp), peach (P. persica) and pear (Pyrus ssp) trees and bean (Vicia faba L.), potato (S. tuberosum), strawberry (Fragaria ssp) and wheat plants (T. aestivum L.) (Wisniewski et al 1997;Fuller & Wisniewski 1998). Computer software has also been used to analyze recordings of infrared video tape to study all stages of ice formation and to quantify the magnitude of the exotherms observed and their duration (Al-Swedi et al 2013).…”

Elevated atmospheric [CO2] promotes frost damage in evergreen tree seedlings

“…An infrared camera and thermal imaging system (Agema Thermovision 800, Agema Infrared Systems, Danderyd, Sweden) were used to produce freezing exotherms (Wisniewski, Lindow & Ashworth 1997) in whole, detached leaves, cooled at 8°C h -1 on 24 October 1996. The cooling chamber consisted of a hollow, cylindrical tower made of styrofoam with internal dimensions of 19·5 × 86·5 cm.…”