Large areas of forests were radioactively contaminated by the Fukushima nuclear accident of 2011, and forest decontamination is now an important problem in Japan. However, whether trees absorb radioactive fallout from soil via the roots or directly from the atmosphere through the bark and leaves is unclear. We measured the uptake of radiocesium by trees in forests heavily contaminated by the Fukushima nuclear accident. The radiocesium concentrations in sapwood of two tree species, the deciduous broadleaved konara (Quercus serrata) and the evergreen coniferous sugi (Cryptomeria japonica), were higher than that in heartwood. The concentration profiles showed anomalous directionality in konara and non-directionality in sugi, indicating that most radiocesium in the tree rings was directly absorbed from the atmosphere via bark and leaves rather than via roots. Numerical modelling shows that the maximum 137Cs concentration in the xylem of konara will be achieved 28 years after the accident. Conversely, the values for sugi will monotonously decrease because of the small transfer factor in this species. Overall, xylem 137Cs concentrations will not be affected by root uptake if active root systems occur 10 cm below the soil.

No abstract

Pholiota nameko is a wood-rotting edible mushroom that carries a bipolar A incompatibility factor gene. The linkage analysis of the multiple allelomorphic A factor gene demonstrated that sexual reproduction produced a monospore isolate carrying a new A factor gene in addition to two parental mating types of isolates. However, 10%-30% of the modified monospore isolates could not produce a dikaryon with both of the parental monokaryons by crossing. It is concluded that the bipolar A incompatibility factor gene of P. nameko is constituted of two functional subunits, Aα and A , which might be successively located beside each other with an apparent genetic distance of 0.3 centi-Morgan between them on the same chromosome. Further, some monospore isolates that did not conjugate with both parental monokaryons could produce dikaryons with different monokaryotic stocks with either one of the parental mating types. This result suggests that the crossing capability of these isolates were essentially those for one of the mating types of the parental monokaryons, but that their function for mating activity was made partially by unequal crossingover in the process of sexual recombination.

Pholiota microspora (Berk.) Sacc. (synonym P. nameko) ("nameko" in Japanese) is one of the most popular edible mushrooms, especially in Japan. This species is a type of white-rot fungus that grows on dead or rotten trees in cool-temperate deciduous forests of East Asia, ranging from the Himalayas and China to Japan

A method with potential utility in radiocesium decontamination from timber harvested in Fukushima region, where fallout from the Fukushima Daiichi nuclear disaster was deposited, involves drying the timber and planing away the contaminated wood. The objective of this study was to investigate the influence of drying temperature on the migration of cesium dissolved in the liquid water of sugi (Cryptomeria japonica D. Don) sapwood during the drying process. Small specimens of sugi sapwood impregnated with aqueous cesium chloride (CsCl) solution were dried at 20 C or 90 C, and the migration of CsCl during drying was examined by means of X-ray imaging. The results of this study indicate that the drying of sugi sapwood at any temperature causes surface accumulation of dissolved cesium, which is affected by both the drying temperature and grain orientation of the surface. Statistical analysis confirmed that a high drying temperature causes greater surface accumulation of CsCl during drying. We recommend using higher temperatures to dry sugi sapwood when employing the drying/planing method for radiocesium decontamination from timber.