抄録
This study presents a new technique to investigate the dynamic behavior of fine roots of Pinus densiflora (Japanese red pine) seedlings with very high sensitivity in the order of sub-nanometer by using a novel optical interference method called statistical interferometry. Principle of the statistical interferometry is based on the statistics of a fully developed speckle field, which is generated when a rough surface is illuminated by the laser light. The technique facilitates to obtain minute root growth measurements in very short periods, in the order of sub-seconds. Three types of pine seedlings were investigated, where two types were infected with ectomycorrhizas called, Pisolithus sp. (Ps) and Cenococcum geophilum (Cg), while the third, which was used as the control, was without any fungal infection. Further, the impact of air pollution caused by photochemical oxidant; ozone, on the growth behavior of these seedlings were distinguished. In experiments, two points on a root 3 mm apart were illuminated by laser beams and the elongation was measured continuously by analyzing speckle patterns successively taken by a CCD camera. It was found that the root growth rates of ectomycorrhiza-infected seedlings were significantly higher than that of non-infected seedlings, and Ps-infected roots showed the highest root growth rate. Moreover, the effect of ozone stress was clearly observable in non-infected seedlings, while the impact on ectomycorrhiza infected seedlings depended on the ozone concentration and the period of exposure. Our study revealed that the statistical interferometry offers high potential with a sub-nanometer sensitivity for measuring crucial dynamic parameters of biological objects in very short-periods as well as with high frequency, suggesting that exploration of new insights on dynamic behavior of living materials becomes much feasible in future studies.
