Using Chlorophyll Fluorescence (Fv/Fm) as an Objective, Sensitive, and Efficient Method to Determine Cane Tissue Hardiness of Grapevines

Abstract

Determining hardiness levels of plant tissues is a prerequisite for cold hardiness research. LT50 determined by browning or regrowth tests is reliable and the most widely used means for assessing woody vegetative tissue viability. It is, however, time consuming and subjective. Although chlorophyll fluorescence (Fv/Fm) has been recently proposed to measure tissue injury for leaf and bud tissues, there are no reports on use for assessing viability of freezing-stressed woody tissues. We investigated the Fv/Fm changes of 1- and 2-year-old canes of Concord grapevines during the cold acclimation and compared these with browning and regrowth tests. The data showed that: 1) There were statistically significant, positive relationships between Fv/Fm changes and freezing temperature treatment that caused tissue injury. The best fit curvilinear equations were obtained; 2) The time of measuring chlorophyll fluorescence post-stress was important. Immediate assessment was not as precise in separating cold hardiness difference as when the tissue was measured 1 week later (at the time of browning test evaluation) or 4 weeks later (at the time of regrowth test evaluation). Assessment 20–26 h post-stress was equivalent to the 1-week or 4-week assessment. These data suggest that chlorophyll fluorescence (Fv/Fm) is a useful practical tool for assessing vegetative tissue viability. Importantly, it is rapid, simple, and objective.