Influence of Low/High Temperature on Water Status in Developing and Maturing Rice Grains

Changes in NMR Relaxation of Rice Grains, Kernel Quality and Physicochemical Properties in Response to a High Temperature after Flowering in Heat-Tolerant and Heat-Sensitive Rice Cultivars

“…The changes in these values of 'Chikushi 64' and 'Nikomaru' showed similar tendency while those of 'Hinohikari' showed a different response to each temperature as reported by Funaba et al (2006). Therefore, only the results of 'Chikushi 64' grains are shown in Fig.…”

“…The high temperature increased the dry weight and decreased the water content in 'Hinohikari', and both the long and short fractions of T 1 . T 1 values between 100 ms and 3 s are thought to show the existence of free water that is present mainly in vacuoles (Hills and Remigereau, 1997;IwayaInoue and Nonami, 2003;Iwaya-Inoue et al, 2004a, 2004bFunaba et al, 2006). The changes of T 1 in the 'Hinohikari' grains were closely related to the water content until the mid-mature stage.…”

“…For example, the japonica cultivars 'Hatsuboshi' and 'Hinohikari' produce chalky grains at temperatures above 27ºC, showing sensitivity to high temperature (Wakamatsu et al, 2007). The grains of 'Hinohikari' grown at 30ºC had white-backed kernels in 85% of the ripened grains and no perfect kernels (Funaba et al, 2006). Recently, the cultivar 'Nikomaru', with tolerance to high temperatures has been bred (Sakai et al, 2007), as well as a similarly tolerant line, 'Chikushi 64'.…”

“…Previously, we showed that the NMR relaxation time of 'Hinohikari' grains offer a good non-destructive test that reveals physical changes in rice grains exposed to temperature stress (Funaba et al, 2006). Changes in the NMR spin-lattice relaxation time (T 1 ) in rice grains were closely related to the quantity of water in the grains until the mid-mature stage, whereas the spin-spin relaxation time (T 2 ) was a more sensitive diagnostic indicator of the accumulation of dry matter and kernel quality, both of which were influenced by temperature stress.…”

“…Spin-lattice relaxation time (T 1 ) of the samples was measured based on the procedure described by Funaba et al (2006). A 1 H-NMR spectrometer with a magnet operating at 25 MHz for 1 H (M25A, JEOL Ltd., Tokyo, Japan) was used for the measurement of T 1 .…”