Freezing avoidance by deep undercooling of tissue water in winter-hardy plants

Phylogenetic Analyses inCornusSubstantiate Ancestry of Xylem Supercooling Freezing Behavior and Reveal Lineage of Desiccation Related Proteins

“…Temperature creates a selective pressure on plants growing in temperate climates and has affected their geographical distribution based upon a capacity to survive seasonal thermal fluctuations (Smithberg and Weiser, 1968;Sakai and Weiser, 1973;George et al, 1974;Becwar et al, 1981;Gusta et al, 1983). In woody plants, two distinct and fundamentally different strategies for the seasonal survival of subzero temperatures have evolved: freeze tolerance (nonsupercooling) and freeze avoidance (supercooling; Burke et al, 1976;George et al, 1982). Freezing behavior strategies employed by a woody plant vary from tissue to tissue and are species specific.…”

“…In nonsupercooling tissues, ice formation is initiated within extracellular spaces and generates a dehydrative vapor pressure gradient between extracellular ice and intracellular water. Nonsupercooling cells readily desiccate in response to extracellular ice formation (George et al, 1982; and are capable of surviving low temperature extremes (Guy et al, 1986) due to an inherent capacity to tolerate desiccation Fujikawa et al, 1997). In supercooling tissues, ice may also initiate in extracellular spaces; however, cells are thought to resist intracellular desiccation (Burke et al, 1976;George et al, 1982;Wisniewski and Ashworth, 1985;Fujikawa et al, 1994) and maintain intracellular water in a nonequilibrium condition.…”

Response of Xylem Ray Parenchyma Cells of Red Osier Dogwood (Cornus sericea L.) to Freezing Stress (Microscopic Evidence of Protoplasm Contraction)

“…Similar cells were also observed in the wood tissue of flowering dogwood (Cornus florida L.) after exposure to freezing stress (Ristic and Ashworth, 1993b). Intracellular ice formation has been proposed to be the source of freezing injury, but only in wood tissues that exhibit the deep supercooling characteristics (Burke et al, 1976;George and Burke, 1977;George et al, 1982;Ashworth et al, 1983). It is known that red osier dogwood does not exhibit deep supercooling characteristics (Hanison et al, 1978;Malone and Ashworth, 199 1).…”

“…Current concepts of freezing resistance recognize two mechanisms by which woody plant tissues survive freezing temperatures: freezing avoidance and freezing tolerance (Burke et al, 1976;George et al, 1982;Wisniewski and Ashworth, 1986). Tissues that survive low temperatures by freezing avoidance display deep supercooling characteristics.…”

“…Tissues displaying freezing avoidance are moderately hardy and cannot survive temperatures below -4OOC (George et al, 1974;Burke et al, 1976;Becwar et al, 1981). Tissues that resist low temperatures by freezing tolerance lose their cellular water to extracellular ice (George et al, 1982). During freezing, ice forms outside the living cells at temperatures slightly below O°C and grows in extracellular spaces.…”