Non-destructive visualisation in three dimensions of freezing events in flowers of blackcurrant ( Ribes nigrum L.) using spin-echo NMR microscopy

Flowers of blackcurrant ( Ribes nigrum L.) were subjected to freezing stress in vivo, and the resulting damage examined in three dimensions using a spin-echo nuclear magnetic resonance imaging sequence. Increased signal intensity was detected in the damaged flowers, particularly at the base of the style, in T 2-weighted images. This is thought to be the result of intracellular freezing, which causes membrane damage and leakage of cellular contents. It is proposed that this represents the main site of damage within the flowers. The imaging of flowers of differing developmental ages showed larger increases in signal from fully open flowers after freezing damage compared with those in the initial stages of bud, suggesting that the enclosed nature of the flower buds may have a protective effect on the sensitive stylar base. The use of three-dimensional nuclear magnetic resonance imaging provides a rapid and effective means for the visualisation of freezing events within floral tissues; the effective resolution of the images enables greater accuracy and clarity in interpretation than hitherto possible in two dimensions.