The Role of Bacterial ICE Nucleation in Frost Injury to Plants

Abstract

The science of plant pathology is largely a study of the mechanisms, quantifica­ tion, and alleviation of plant stresses due to biological agents. Of obvious importance are the stresses to plants directly caused by infection by various plant pathogenic fungi, bacteria, viruses, nematodes, insects, etc. In such cases, plant stress is due either to direct damage to plant tissue or to an alteration in normal plant metabolism (43). Some biological agents, such as the fungi that form mycorrhizae with plant roots, may even reduce plant stress in certain situations and increase stress in others (4). Plants may also be stressed directly and indirectly by various physical factors such as high or low temperatures (57) or air pollutants (36). A wealth of information exists on the direct effects of low temperatures (57) or air pollu­ tants (36) on plant health. Physical stresses such as temperature (57) or air pollutants (36) may also influence the subsequent damage of plants incited by certain plant pathogens. The converse is also true in some situations. Root­ infecting plant pathogens, for example, can make plants more susceptible to damage due to high temperatures or drought. It is clear that the interaction of the biological and physical environments of plants determines the extent of plant stress. Many more subtle interactions between microorganisms and plants have also been reported. Bacteria living on the surfaces of healthy leaves and roots have been reported to increase plant growth, possibly by production of one or more plant growth regulators (86). Conversely, some bacteria isolated from root surfaces have been shown to be detrimental to root and p,lant growth (117). Frost injury is a serious abiotic disease of plants. Losses in plant production