A research team led by Associate Professor Ishii Roaki, Ph.D., and doctoral student Azuma Wakana from the Kobe University Graduate School of Agricultural Science has discovered that the water storage tissue that they recently found in the world's tallest tree, Sequoia sempervirens (coast redwood), which can reach heights up to 115 meters (379 feet), is also found in Japan's tallest trees, Cryptomeria japonica (Japanese cedar). The results of this research were published online on on 4 September 4, 2015 in the journal Trees. The article is titled “Function and Structure of Leaves Contributing to Increasing Water Storage with Height in the Tallest Cryptomeria japonica Trees of Japan.” How do tall trees supply water to pinnacle leaves? Until now, it was thought that the highest leaves of tall trees suffered from constant water deficit because the water absorbed by the roots had to be transported a long way. Even among tree physiologists, most research focused on identifying the constraints to water transport, which would define the limits of tree height. In 2012, Professor Ishii's research group climbed the world's tallest redwoods, and collected leaf samples from various heights. They discovered that, with increasing height in the tree, the proportion of "xylem tissue" which transports water from the roots decreased, whereas the proportion of "transfusion tissue," which stores water, increased. The team inferred that in these redwoods, the stored water came from moisture such as fog and dew absorbed through the leaf surface. On September 9, 2014, the group conducted field work in Japan’s Akita Prefecture to determine whether similar foliar water storage functions existed in Japan's tallest cedar trees, a close relative of the coast redwood, that can reach heights of over 50 meters (164 feet).
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