Factors Influencing Freezing of Supercooled Water in Tender Plants¹

Abstract

may increase the tolerance of tender plants to frost (9). There is essentially no information on how protective mechanisms interact with the natural physical environment around plants, particularly with respect to the stability of supercooled water in the plant. There is an immediate need for a basic understanding of what does occur during periods of light frost. ABSTRACT Seedlings of beans (Phaseolus vulgaris), corn (Zea mays),and tomatoes (Lycopersicon esculentum) were grown in the greenhouse and then exposed to controlled freezing conditions in a growth chamber. Variables were adjusted to determine the influence of plant water potential, freezing time, and external dew formation on the seedlings' susceptibility to frost injury. Freezing, detected visually and by release of latent heat, progressed rapidly throughout plants with high water potential and was always lethal. Spreading of the ice phase was impeded in plants with low water potential. In this case, the freezing injury ap• peared as spots on the leaves which gradually enlarged to encompass the entire leaf as the exposure continued. In general, the plant water supercooled before freezing. Supercooled water within the plant appeared to be internally nucleated if the leaf temperature remained above th atmospheric dewpoint temperature. Under these conditions root temperature, plant water energy, and duration of the freezing period all influenced the stability of the supercooled water. On the other hand, external inoculation prevailed when the freezing temperatures were accompanied by condensation of water from the air and subsequent formation of ice crystals on the leaves. One important exception was noted when ice on corn seedling leaves failed to nucleate the supercooled internal plant water with a potential of -18 bars. W HILE freezing damage to plants has been studied extensively during the past 50 years, most of the emphasis has been directed toward plants that have the ability to cold-harden, particularly biennials and perennials which survive low winter temperatures in a dormant stage (12). An equally important problem is frost damage to growing, nonhardened plants. Frost damage to seedlings or immature crops results in serious economic losses. This phase of the frost problem has received relatively little research aside from air temperature control which may be attempted for orchards and other specialty crops during periods of unseasonably cold weather (10). AdditionalGrowing plants may survive freezing temperatures in two ways. The water in the plant may supercool and not form ice crystals, or the plant may tolerate some ice crystals without having a significant number of cell membranes ruptured (6). Single (15) reported that wheat plants could, under certain conditions, be kept at temperatures of -3 to -5C "almost indefinitely" without having ice form in the tissue, provided there were no ice crystals in the external environment. When ice crystals do form in the tender, growing tissue of many plants, the cells rupture and die. However, Olien (1...

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

“…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.…”

“…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.…”

“…Although the abundance of ice nuclei on plants can be estimated by freezing droplets of plant macerates or small portions of plant tissue Ashworth and Kieft, 1995), these procedures are destructive and do not provide information concerning the location of ice nucleation. Likewise, ice formation in intact plants can be readily detected by measuring the heat that is released upon the freezing of the water in the plant (Cary and Mayland, 1970;Quamme et al, 1972;Burke et al, 1976;Proebsting et al, 1982;Ashworth and Davis, 1984;Anderson and Ashworth, 1985;Ashworth et al, 1985;Andrews et al, 1986;Yelenosky 1991aYelenosky , 1991bAshworth and Kieft, 1995). However, even when arrays of temperature-measuring devices are attached to plants, the actual site of ice initiation and the temperature at the site where ice nucleation occurred can only be inferred (Ashworth et al, 1985).…”

K+(Rb+) and Ca2+ fluxes in young winter wheat plants exposed to sub‐zero temperatures

“…1). Ice formation was probably extracellular, since the cooling rate was slow (Levitt 1966, Olien 1967, Dowgert and Steponkus 1983, the surface of the piants was well wetted (Cary and Mayland 1979) and ice was placed in contact with the test plants.…”

Plant Cold Hardiness

“…Ice formation in intact plants can be readily detected by measuring, with thermocouples, the heat that is released upon the freezing of the water in the plant (Ashworth, 1992;Cary and Mayland, 1970;Proebsting, et aI., 1982;Quamme, et aI., 1972). Nevertheless, even when arrays of temperature measuring devices are attached to plants, the actual site of ice initiation and the temperature at the site where ice nucleation occurred can only be inferred (Ashworth, et aI., 1985).…”