Mechanisms of fruit cell expansion with intact water potential measurements

水势测量通常与干湿仪一起进行，使用切除的组织。当组织生长时，然后，如果在延伸区切除取样，众所周知，壁松弛将发生。如果在延伸区发生由于切除引起的壁面松弛，用干湿计测量水势可能无法准确进行，因为壁面松弛会使水势的测量值降低。然而，湿度计只是一种测量完整植物体内水势的方法。因此，对干湿测量技术的改进有助于完整植株水势的测定。为了改进干湿测量，试图将干湿计的输出量增加3倍，方法是在干湿计的传感器上加装一个热电堆。热电堆由3个热电偶结组合而成。输出一个热电偶产生480 nV每0.1兆帕。虽然本研究制作的热电堆每0.1 MPa的输出功率应为480 nV的3倍，但热电堆的输出功率仅为单个热电偶的2.0 ~ 2.4倍。这种故障可能是由于使用焊料连接热电偶。在热电偶之间的焊接过程可能产生额外的噪声以降低热电偶输出。用压力探针和干湿计测定了番茄果实和水稻胚乳细胞的水分状况。高夜间温度降低了水稻胚乳细胞的水势梯度，导致高温下水稻产量下降。

Water potential measurements are usually conducted with the psychrometry by using excised tissues. When tissues are growing, and then, if excision is made in the zone of elongation for sampling, it is known that wall relaxation will take place. If wall relaxation due to excision takes place in the zone of elongation, water potential measurements with the psychrometer may not be accurately conducted because wall relaxation will make the measured value of water potential shift lower. However, the psychrometry is only a method which allows to measure the water potential in intact plants. Thus, improvement of the psychrometry is helpful for measuring water potential in intact plants. In order to improve the psychrometry, the output of a psychrometer was attempted to multiply by 3 times by malting a thermopile for the sensor of the psychrometer. The thermopile was made by combining 3 thermocouple junctions. Output of one thermocouple yields 480 nV per 0.1 MPa. Although the thermopile made in the present study should yield 3 times of 480 nV per 0.1 MPa, the output of the thermopile yielded only 2.0 to 2.4 times of that of one thermocouple. This failure might be due to connection between the thermocouples by using solder. The process of soldering between the thermocouples may yield the extra noise to reduce the thermocouple output. The water status of intact tomato fruit and endosperm cells of rice plants was measured with the pressure probe and psychrometers. Cell expansion in both plants was associated with the gradient of the growth-induced water potential High night temperature reduced the water potential gradient in endosperm cells of rice, resulting in yield decrease of rice at high temperature.