Khan A A, Zeng G W
Department of Horticultural Sciences, New York State Agricultural Experiment Station, Cornell University, Geneva, New York 14456.
Plant Physiol. 1985 Apr;77(4):817-23. doi: 10.1104/pp.77.4.817.
;Grand Rapids' lettuce Lactuca sativa L. seeds germinate readily at 15 degrees C but poorly at 25 degrees C in darkness. When held in dark at 25 degrees C for an extended period, the ungerminated seeds become dormant as shown by their inability to germinate or transfer to 15 degrees C in darkness. Induction of dormancy at 25 degrees C was prevented by exposure to CN(-), azide, salicylhydroxamic acid (SHAM), dinitrophenol, and pure N(2) as determined by subsequent germination at 15 degrees C on removal of inhibitors. The effectiveness of inhibitors to break dormancy declined as dormancy intensified. At relatively low levels, CN(-), SHAM, and azide promoted dark germination at 25 degrees C while at high levels they were inhibitory. Uptake of O(2) by seeds held at 25 degrees C for 4 days in 1.0 millimolar KCN was inhibited by 67% but was promoted 61% when KCN was removed. Correspondingly greater inhibition (79%) and promotion (148%) occurred when 1.0 millimolar SHAM was added to KCN solution. When applied alone, SHAM had little effect on O(2) uptake. These data indicate that Cyt pathway of respiration plays a dominant role in the control of both dormancy induction and germination of lettuce seeds, and ;alternative pathway' is effectively engaged in presence of CN(-). The channeling of respiratory energy use for processes governing germination or dormancy is subject to control by physical and chemical factors.A scheme is proposed that illustrates compensatory use of energy for processes controlling dormancy induction and germination. A block of germination, e.g. by low water potential polyethylene glycol solution or a supraoptimal temperature spares energy to be utilized for dormancy induction while a block of dormancy induction by low levels of CN(-) (similar to GA and light effects) drives germination. Blocking both processes by inhibitors (e.g. CN(-), CN(-) + SHAM) presumably leads to accumulation of ;reducing power' with consequent improvement in O(2) uptake and oxidation rates of processes controlling germination or dormancy induction upon removal of the inhibitors.
大急流城生菜（Lactuca sativa L.）种子在15摄氏度的黑暗环境中很容易发芽，但在25摄氏度时发芽情况很差。当在25摄氏度的黑暗环境中放置较长时间后，未发芽的种子会进入休眠状态，这表现为它们无法发芽，或者转移到15摄氏度的黑暗环境中也不能发芽。通过在去除抑制剂后于15摄氏度下后续发芽测定发现，暴露于氰化物（CN⁻）、叠氮化物、水杨羟肟酸（SHAM）、二硝基苯酚和纯氮气中可防止在25摄氏度时诱导休眠。随着休眠加剧，抑制剂打破休眠的效果会下降。在相对较低水平时，CN⁻、SHAM和叠氮化物促进种子在25摄氏度的黑暗环境中发芽，而在高水平时它们具有抑制作用。在1.0毫摩尔KCN中于25摄氏度下放置4天的种子对氧气的吸收被抑制了67%，但去除KCN后促进了61%。相应地，当向KCN溶液中添加1.0毫摩尔SHAM时，抑制作用更强（79%），促进作用更大（148%）。单独使用SHAM时，对氧气吸收几乎没有影响。这些数据表明，细胞呼吸途径在生菜种子休眠诱导和发芽的控制中起主导作用，并且在存在CN⁻的情况下“交替途径”有效地发挥作用。用于控制发芽或休眠过程的呼吸能量利用途径受到物理和化学因素的控制。提出了一个方案，该方案说明了能量在控制休眠诱导和发芽过程中的补偿利用情况。例如，通过低水势聚乙二醇溶液或超适宜温度阻止发芽可节省能量用于休眠诱导，而低水平的CN⁻（类似于赤霉素和光的作用）阻止休眠诱导则会驱动发芽。用抑制剂（如CN⁻、CN⁻ + SHAM）同时阻断这两个过程可能会导致“还原力”的积累，从而在去除抑制剂后提高控制发芽或休眠诱导过程的氧气吸收和氧化速率。
