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We investigated the distribution of radiocesium (134Cs and 137Cs) in three orchards in Tsukuba, 170 km southwest from the Tokyo Electric Power Company’s Fukushima Daiichi Nuclear Power Plant 9 months after the accident. The radiocesium was distributed mainly in the surface soil. The distribution of radiocesium differed between deciduous and evergreen plants. In deciduous blueberry (Vaccinium virgatum Aiton), the concentration was high in the old branches because the bushes had no leaves at the time of the accident. Therefore, the concentration per bush was greater in unpruned than in pruned bushes. More radiocesium was present in the trunk and rootstock of each bush, although the concentration was low. In evergreen Satsuma mandarin (Citrus unshiu Marcow), the concentration was high in the leaves, and it was higher in old leaves that expanded before the accident than in new leaves that expanded after the accident, because the old leaves were contaminated by direct deposition of the fallout. However...

We investigated changes in radiocesium concentrations in a Japanese chestnut (Castanea crenata Sieold & Zucc.) orchard in Ibaraki prefecture for 3 years after the Tokyo Electric Power Company’s Fukushima Daiichi nuclear power plant accident in March 2011. The radiocesium concentrations in the aboveground organs of Japanese chestnut trees were almost the same, while the concentration in the roots was the lowest among all the organs investigated. The concentration of radiocesium decreased exponentially for 3 years in nuts, leaves and current shoots. The radiocesium concentrations in soils were higher in the surface layer, and the trend of an annual decrease in radiocesium in the soils was similar to that of the natural decay of radiocesium. The transfer factor of radiocesium from soils to nuts of Japanese chestnut decreased annually. These results suggest that radiocesium adhered directly to the aboveground organs of Japanese chestnut trees in March 2011, and that the accumulation of radiocesium in ...

We investigated changes in the radiocesium concentration in a blueberry (Vaccinium virgatum Aiton) orchard in Fukushima prefecture to clarify the radiocesium contamination for 3 years after the Tokyo Electric Power Company’s Fukushima Daiichi nuclear power plant accident occurred in mid-March 2011. In the aboveground part of blueberry bushes, the concentrations of radiocesium in branches that were directly affected by radioactive fallout were the highest among the samples investigated, and the concentrations in fruits were the lowest. The concentration of radiocesium decreased exponentially in the fruits and leaves over 3 years. The radiocesium concentrations in soils were higher in the surface layer. The amount of radiocesium in organic matter on the soil surface under the canopy greatly decreased from 2011 to 2012. The transfer factor of the radiocesium from soil to blueberry fruits decreased annually. These results suggest that radiocesium adhered directly to the aboveground organs of blueberry...

従来のTDR枝内水分測定法を用いてウンシュウミカンの水分状態を把握する際，温度依存性，プローブの挿入深度の誤差による測定開始時の値のバラツキが問題となっている．そこで，温度依存性は補正式を作成し，値のバラツキは年間の枝内水分状態が安定する時期を基準点とした相対値の利用を検討した．その結果，枝内温度とTDR値の間には高い相関が認められ，補正式を導き出した．基準点は測定時の気温が30℃以上で土壌が湿潤状態の場合，年間の枝内水分がピークとなる7月上中旬が適していることが明らかとなった．温度補正後のTDR相対値（Rrev）と葉内最大水ポテンシャル（LWP）との間には，強い相関が認められた．月別では7月の相関係数は0.888，8および9月は約0.7となった．10月以降は0.435と中程度の相関となった．一方，TDR値を枝内体積含水率（VWC）に変換した値は，いずれの月においても相関係数は0.3以下であった．さらに，Rrevと気温を用いたLWPの予測式の決定係数は0.712となり，高い精度で予測できる．以上より，本方法は従来のVWC変換値に比べLWPとの相関が高く，樹体の水分状態を一定程度把握できると考えられる．

Hydraulic conductance is an important index of water flow in plants. We constructed a simple device for measuring the relative hydraulic conductance of fruit tree shoots. The values of vines (kiwifruit and grape) were the highest among 17 species of major temperate fruit trees, followed by deciduous trees (e.g. chestnut, Japanese pear, and peach), evergreen citrus trees (e.g. Kawanonatsudaidai and Satsuma mandarin), and loquat. The diameter and number of vessels and total vessel area in shoots were calculated with image analysis software from photomicrographs of 13 of the species. The diameter of the vessels was largest in vines (kiwifruit and grape), followed by persimmon and chestnut, and smallest in deciduous trees (e.g. apple and Japanese apricot), citrus, and loquat. Relative hydraulic conductance had a higher correlation with the water flow index (Σr4/S × (xylem ratio)), calculated from the diameter and number of vessels in the xylem according to the Hagen–Poiseuille law, and than with total vessel area per unit of shoot cross-sectional area.

Electrical impedance analysis was conducted using 4-year-old potted Satsuma mandarin (cv. Toyofuku-wase) trees to measure tree water status. Two electrodes were inserted to the tee trunk 3 cm apart and 3 mm in depth, and then capacitance and resistance at four frequencies of alternative current (0.1, 1, 10 and 100 kHz) were detected using an LCR meter which was connected to the electrodes. During drought treatments performed in June 2005 and October 2005, transpiration and photosynthesis rates in the leaves and the changes of the tree trunk diameter were simultaneously measured using a portable photosynthesis system and dendrometers, respectively. Resistance at the four frequencies increased as the duration of the drought treatment was longer, on the contrary capacitance, transpiration rate and photosynthesis rate decreased. Tree trunk diameter has daily fluctuated and then dramatically shrank at day 0 in June treatment and day 2 in October treatment. Relationship between parameters of the electrical impedance and other water related parameters was discussed.

赤外カメラを使った樹体の水分ストレス程度を診断する手法の開発を試みた．ブドウは水分ストレスにより，枝の基部に近い葉の一部が壊死し，壊死した部分の面積は，水分ストレスが生じる時間が長くなるにつれて拡大した．壊死した部分は，赤外カメラで撮影した画像により明確に区別できた．一方，ウンシュウミカンでは，葉柄基部に離層が生じた後，落葉した．したがって，落葉する前の葉の水分含量を正確に測定する必要があると考えられた．そこで，水分含量の異なる濾紙を赤外カメラで撮影し，キャリブレーションを行った後，ウンシュウミカン葉の撮影画像を画像処理ソフト（Image Pro-plus）を使って背景処理することにより，水分ストレスの有無による画像の輝度の違いが認められた．赤外カメラの画像から推定した水分指数と実際に熱風乾燥した水分含量との間に有意に高い相関が認められた．これらの結果から，赤外カメラによる葉の水分含量の推定は，可能であると考えられた．

Electrical impedance analysis was conducted from February to May in 2005 using current year shoots of four fruit species (grape, apple, kiwifruit and Satsuma mandarin) . When series resistance (Rs) and reactance (X) was plotted on the complex plane, three parameters (Rs measured at extremely low frequency (Z0) and high frequency (Z∞) and an angle of arch (2φ) ) were calculated. Z0 was decreased from the beginning of determination to April in grape and mandarin, and from March to April in kiwifruit, while in apple it was unchanged at the beginning of determination, and then was decreased after bud break. In grape and kiwifruit Z0 turned to be the minimum during bleed of xylem exudates, after that it slightly increased.Z∞ was decreased in apple and mandarin, while it fluctuating within small range in grape and kiwifruit. The value of 2φ was increased in all four species. Correlation coefficient between shoot water content and Z0 was significant in all four species, and of its absolute value was the highest in grape, followed by kiwifruit and mandarin, and the lowest in apple. These data showed that Z0 might be a suitable indicator for the status of sap flow.