Characteristic Changes in Relaxation Times of Water Protons in Vigna radiata Seedlings Exposed to Temperature Stress |
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Authors: | Iwaya-Inoue, Mari Yoshimura, Kazuhisa Yamasaki, Hideo Kaku, Shosuke |
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Affiliation: | 1Biological Laboratory, College of General Education, Kyushu University Ropponmatsu, Fukuoka, 810 Japan 2Chemistry Laboratory, College of General Education, Kyushu University Ropponmatsu, Fukuoka, 810 Japan 3Department of Biology, Faculty of Science, Kyushu University Hakozaki, Fukuoka, 812 Japan |
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Abstract: | Water protons in hypocotyl tissues from etiolated seedlingsof Vigna radiata that were exposed to temperature stress showedcharacteristic relaxation behaviors for 1H-NMR. Cold stresstreatment (0C) caused gradual prolongation of NMR relaxationtimes (T1). After exposure of tissues to cold stress for 24h, T1 returned to the initial value as a result of subsequentincubation at normal temperature (20C). By contrast, heat stresstreatment (40C) induced a time-dependent decrease in T1, whichdid not return completely to the initial value upon subsequentincubation at 20C after exposure to heat stress for 4 h. Weexamined changes in various physical factors that influencethe response of T1 to temperature stress, namely, water contentand the concentrations of protein, diamagnetic (K+, Na+, Ca2+and Mg2+) and paramagnetic (Mn2+ and Fe2+) ions in the tissues.From the relationships between T1 and these factors in vitro,we could not interpret the responses of T1 to the temperaturestress only in terms of a change in water content. A synergisticeffect of an Mn2+ -protein complex and pH might be essentialfor the mechanism of changes in T1 that are due to cold stress.The influence of heat stress on structural water in tissuesis discussed in terms of water-protein interactions. (Received December 28, 1992; Accepted May 6, 1993) |
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