Effects of simultaneous application of cool air and CO2 were evaluated on initial growth of strawberry (‘Yotsuboshi’). However, these treatments did not increase shoot dry weight, the root fresh and dry weight were increased. Natural abundance of 13C of both parts are decreased significantly by the treatment, these results suggested that applied CO2 was absorbed and translocated to the root. Even though CO2 concentration has been maintained around 600 μmol mol－1 in the day time, CO2 use efficiency evaluated by 13C natural abundance was estimated only 51%. Natural abundance of 13C could be an indicator for developing more efficient CO2 application method.
Grafted mango trees tend to die when the graft union is submerged in water. In this study, we investigated the root vigor using triphenyl tetrazolium chloride (TTC) reduction tests in relation to carbohydrate distribution and defoliation, when the trees were submerged up to 5 cm above the graft union. Immediately after the commencement of flooding treatment, the root sugar content increased due to the decrease in the root vigor. Although the root vigor did not recover during flooding treatment, the root sugar content gradually decreased to a level not significantly different from that in the non-treated control. Defoliation in flooding trees varied greatly and was correlated with the sugar content of the roots and wood of the rootstock. As the root vigor during the flooding treatment was positively correlated with root sugar content, it was considered that the decrease in root vigor due to flooding was not only caused by oxygen deficiency but also by the decreased supply of photoassimilates from the scion.
On the night of July 11, 2020, the giant Cryptomeria japonica tree collapsed during the heavy rainfall event in Okute Town, Gifu. The purpose of this study is to clarify the characteristics of the root system of the fallen tree together with the weather conditions such as heavy rainfall at the time. In July 2020, there were few sunshine hours which could induce higher water contents of the tree and soils. A large area of decay was observed in the root system close to the center of the stem and roots remaining in the soil showed signs of stripping. Using a laser scanner, the three-dimensional structure of the tree was digitally reproduced, and the volume of root system was estimated to be 43.2 m3. The diameter of the root-soil plate and the volume ratio to the aboveground part suggested that the root system of the tree was relatively small compared with those of other C. japonica trees. Based on the evaluation of the root system and weather conditions, the soil reinforcement by roots could be reduced due to decay during the long-term growth periods, and the balance between the above- and below-ground parts of the tree might be disrupted by the increase in the water contents of the tree and soils caused by prolonged rainfall and lack of sunlight.