Hy. Jiang et al., Efficacy of chlorophyll fluorescence as a viability test for freeze-stressed woody grape tissues, CAN J PLANT, 79(3), 1999, pp. 401-409
Woody-tissue cold hardiness and chlorophyll fluorescence of Concord (Vitis
labruscana Bailey) grapevines were measured every 2 wk from late September
to mid-December 1997. Plant efficiency analyser (Hansatech Ltd., King's Lyn
n, UK) was used to measure chlorophyll fluorescence after a laboratory cont
rolled freeze stress. From five preliminary experiments, valid chlorophyll
fluorescence measurements were obtained from the cane surface with periderm
removed, under similar to 2700 mu mol m(-2) s(-1) and 10 min dark adaptati
on after 24-30 h post stress. For large samples, dark adaptation was not ne
cessary if only the Fv/Fm (ratio of variable fluorescence to maximum fluore
scence) was of interest. This ratio was positively correlated with freeze-s
tress temperatures and negatively correlated with tissue injury. The Fv/Fm
temperature inflection point was positively correlated with LT50 (temperatu
re at which 50% of the sample is injured), calculated from the regrowth tes
t. The Fv/Fm ratio was a sensitive, reliable, objective, and rapid method o
f assessing woody-tissue viability after a freeze-thaw episode during cold
acclimation. An Fv/Fm-50 was proposed as an indicator of the injury thresho
ld.