Determination of the rate of 18F-labeled water movement to the leaf and its association with water relations in acid soil-tolerant rice varieties

Abstract

The visual symptoms of damage by acid sulfate soil look quite similar to those due to soil moisture deficit. The present paper is to confirm if acid soil-tolerance is associated with drought tolerance in terms of leaf water potential, transpiration, and dry matter production. Seedlings of seven acid soil-tolerant (acid-tolerant), and three acid soil-intolerant varieties (acid-intolerant) were subjected to low pH conditions (pH 3.8) for 48 hours. The rate of water uptake was determined continuously by measuring radioactivity in the collar part (target area) of rice leaves exposed to 18 F-labeled water ( 18 F-water) using a Positron Emitting Tracer Imaging System (PETIS). The PETIS measurement showed that the radioactivity in the target position of leaves of acid-tolerant varieties increased faster than that of the intolerant varieties after the 18 F-water was applied into the vial. In the plants subjected to low pH conditions, the transpiration rate (Tr) and leaf water potential ( ) decreased in both acid-tolerant and intolerant varieties. However, the extent of reduction was less in the acid-tolerant varieties than in the intolerant ones. Moreover, the dry matter production rate of the acid-tolerant varieties was significantly higher than that of the acid-intolerant ones in the low pH conditions. This study clearly shows that 18 Fwater uptake in a leaf was higher, and water relations were also better maintained in the acid-tolerant varieties compared with intolerant ones, resulting in higher growth rate in the acid-tolerant varieties, when plants were exposed to the acid solution conditions. We conclude that acid soil-tolerance is closely associated with leaf water relations in rice plants.

Research with radiation and radioisotopes to better understand plant physiology and agricultural consequences of radioactive contamination from the Fukushima Daiichi nuclear accident

“…As mentioned earlier, some of the radioactive nuclides applied to our systems were: 14 C, 22 Na, 28 Mg, 32 P, 33 P, 35 S, 42 K, 45 Ca, 54 Mn, 55 Fe, 59 Fe, 65 Zn, 86 Rb, 109 Cd, 137 Cs, etc. In the case of macroscopic system, tracer movement from root to up-ground part of Arabidopsis was visualized using various radioactive nuclides.…”

“…However, the lower picture showed clear difference of the water distribution between heartwood and sapwood parts. Water image of the Japanese cypress showed high amount of water in only outer part of the wood and small amount of water was distributed along the annual ring in inner part Water movement using RI: water movement [28][29][30][31][32][33][34][35] The first trial to analyze water absorption manner was studied using the cowpea plant supplied with 18 F (half-life: 110 min) containing water, which was produced by irradiation of water with He ? beam.…”

“…Everything had to be kept in dark in the 1st generation; then the plant box was introduced in the 2nd generation where only the upper part of the plant was irradiated with light. Finally, the light was off only when camera was on in the 3rd generation so that weak radiation energy from radioisotopes such as 14 C, 35 S and 45 Ca, etc. could be easily detected.…”

“…In the case of macroscopic system, tracer movement from root to up-ground part of Arabidopsis was visualized using various radioactive nuclides. Figure 25 shows how the inorganic elements, namely 22 Na, 28 Mg, 32 P, 35 S, 42 K, 45 Ca, 54 Mn, and 137 Cs, absorbed from roots were transferred to the up-ground part of Arabidopsis within 24 h. Among the nuclides, 28 Mg, 45 Ca, and 54 Mn were very slow to move up-ground part from the root.…”

“…We have been successful in developing the systems both for macroscopic and microscopic imaging. The real-time movement of the elements can now be visualized and analyzed using 14 C, 22 Na, 28 Mg, 32 P, 33 P, 35 S, 42 K, 45 Ca, 54 Mn, 55 Fe, 59 Fe, 65 Zn, 86 Rb, 109 Cd, 137 Cs, etc. The image of 14 CO 2 gas fixation provided that the photosynthate was moved quickly to produce the meristem of the root tip.…”