Department of Plant Sciences, School of Biological Sciences, Madurai Kamaraj University, Madurai 625021 India.
Plant Physiol. 1986 Jan;80(1):264-8. doi: 10.1104/pp.80.1.264.
When Triticum vulgare cv HD 2189 seedlings were grown in the presence of 125 micromolar BASF 13.338 (4-chloro-5-dimethylamino-2-phenyl-3(2H)pyridazinone), the rate of electron transport (H(2)O --> methyl viologen) in chloroplast thylakoids isolated from the treated seedlings was higher (by 50%) as compared to the control at assay temperatures above 30 degrees C. Below 30 degrees C, however, the rate with the treated seedlings was lower than the control rate. The temperature dependence of the rate of photosystem I electron transport (2-6-dichlorophenol indophenol-reduced --> methyl viologen) in the treated system was similar to that in the control. At high temperatures (>30 degrees C), with diphenyl carabazide as electron donor, the rates of electron transfer (diphenyl carbazide --> methyl viologen) were similar in the treated and in the control thylakoids. Direct addition of BASF 13.338 to the assay mixture for the measurement of rate of electron transport (H(2)O --> methyl viologen) in the thylakoids isolated from the control plants did not cause any change in the temperature dependence of photosynthetic electron transport. These results suggested that the donor side of photosystem II became tolerant to heat in the treated plants. Chlorophyll a fluorescence emission was monitored continuously in the leaves of control and BASF 13.338 treated wheat seedlings during continuous increase in temperature (1 degrees C per minute). The fluorescence-temperature profile showed a decrease in the fluorescence yield above 55 degrees C; this decrease was biphasic in the control and monophasic in the treated plants.
当普通小麦（Triticum vulgare cv HD 2189）幼苗在 125 微摩尔 BASF 13.338（4-氯-5-二甲基氨基-2-苯基-3（2H）哒嗪酮）存在的条件下生长时，与对照相比，在高于 30℃的测定温度下，来自处理幼苗的叶绿体类囊体中电子传递（H2O→甲基紫精）的速率更高（增加了 50%）。然而，在 30℃以下，处理幼苗的速率低于对照速率。处理系统中光系统 I 电子传递（2-6-二氯苯酚靛酚还原→甲基紫精）的速率对温度的依赖性与对照系统相似。在高温（>30℃）下，以二苯卡巴肼作为电子供体，处理和对照类囊体中的电子转移（二苯卡巴肼→甲基紫精）速率相似。直接将 BASF 13.338 添加到测定混合物中，以测量来自对照植物类囊体的电子传递（H2O→甲基紫精）的速率，不会导致光合作用电子传递的温度依赖性发生任何变化。这些结果表明，在处理过的植物中，光系统 II 的供体侧对热变得耐受。在连续升高温度（每分钟 1℃）期间，连续监测对照和 BASF 13.338 处理的小麦幼苗叶片中的叶绿素 a 荧光发射。荧光-温度曲线显示在 55℃以上时荧光产率下降；这种下降在对照中是两相的，在处理植物中是单相的。
