Studies on vsualization of freezing behaviors in plants using NMR microscopy and Infra-red thermography and mechanisms of avoiding freeze injuries.

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Behavior of water(freeze or supercool)is crucial for plant tissues to survive subfreezing temperatures as their major component is water. Plants have complex tissues and observation of their freezing behaviors is not necessarily easy with conventional methods. We have developed two novel non-invasive methods to visualize freezing behaviors in plant tissues. These methods proved to be powerful tools to analyze freezing behaviors in plants, which may allow us to reveal mechanisms of cold hardiness, freezing injuries and frost injuries.1. We have established a method to visualize freezing behaviors in complex plant tissues using proton NMR(MIR)microscopy. This depends on a simple mechanism, T_2(spin-spin relaxation time)becomes extremely short when water freezes, which results in a catastrophic decrease in the contrast of NMR images.2. We successfully visualized freezing behaviors in flower buds of several woody species(Malus, Pyrus, Prunus, Cornus, Daphne). This allowed us to find novel … More types of freezing behavior in some of these flower buds and to clearly locate boundary between non-frozen and frozen tissues. Using atest tube method, we detected high ice nucleation activity in the tissue that freezes early.3. Fine freezing behaviors of various leaf tissues of Trachycarpus fortuneii(a cold hardy palm)were revealed using NMR microscopy. Mesophyll cells remained supercooled until-16C. Anti-nucleation activity was detected in the methanol extract from this palm.4. Fine freezing behaviors of various leaf tissues in a cold hardy bamboo species(Sasa kurilensis) were revealed using cryomicroscopy.5. Attempts to visualize freezing events using infra-red thermography have been made since 15 years ago in North America. However, they used raw thermography images (sensitivity being low), the transmission of freezing can be seen in tissues with high water content. In the last few years, the apparatus has been digitized, which allows thermo-images analyzed on computers. Using subtraction images and differential images, we could precisely analyze details of freezing transmission. Less