Mechanical Freezing Injury in Grapevine Trunks

Abstract

Temperatures and related circumferential deformation of grapevine trunks were recorded in vineyards of the Ontario grape growing region during the 1974 and 1977 winter seasons in an effort to gain more information about mechanical winter injury. These field data provided a basis for freezing experiments with freshly cut Gewürztraminer trunk specimens to analyze ice formation and tissue damage in greater detail in the laboratory. A theoretical model capable of simulating trunk temperatures and ice formation was developed. Experimental and simulated data were in good agreement and showed that the degree of ice formation can reach significant levels. The ice crystals will transmit tensile stresses to the trunk tissue capable of rupturing the phellem surface as well as cell walls and vessels in the phloem tissue, which was observed microscopically. A difference in deformation between phloem and xylem will also result during freezing, but cause significant fiber separation in the cambium region only at abnormally low temperatures. The research illustrated the importance of the vine's low moisture concentration and sufficient storage of proteins and carbohydrates for antifreeze action in winter.