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Plant Physics

A sophisticated imaging technique is being used by physicists at Massey University to examine living circulation systems in plant tissue.

Nuclear magnetic resonance (NMR) is used to provide high-quality images of biological substances. A powerful electromagnet is used to align the nuclei of water's hydrogen atoms, the way a compass needle lines up with magnetic north. Radio waves are then used to "flip" the alignment of the nuclei. When the waves are turned off, the nuclei return to their original position, emitting radio waves that are used to generate an image.

Professor Paul Callaghan and his students have built an NMR device to examine how water flows through living tissue. In examining rye grass and wheat grains, his team have been able to identify the active areas of fluid transportation. The results have surprised plant physiologists, indicating movement in areas which were not previously considered likely transportation sites.

"We're the only ones in the world who can measure velocity in vivo, " Prof Callaghan remarks. The fluid in the tiny samples is not moving quickly  40 microns per second, or only 14.4 centimeters per hour.

The research may provide useful information on bruising mechanisms in fruit and how wood takes up preservative solutions.