School of Life Sciences, East China Normal University, Shanghai 200062, PR China.
J Plant Physiol. 2012 Sep 15;169(14):1340-7. doi: 10.1016/j.jplph.2012.05.017. Epub 2012 Jul 15.
Winter dormancy has been extensively studied in many plants, while much less information is available for summer dormancy. Narcissus tazetta var. chinensis is characterized by a prolonged period of summer dormancy during the annual cycle. In the present study, we characterized the nature of dormancy in the controlled growth conditions and investigated the effects of temperature and ethylene on dormancy release. Cessation of growth and senescence of aerial tissues occurred even under conditions favorable for growth, suggesting an endo-dormancy process. Bulbs failed to sprout when they were exposed to low storage temperatures, while high temperature treatment preceding low storage temperatures, or heating interruption during low storage temperatures, could make bulbs sprouting. These results suggest that high temperatures are necessary for endo-dormancy release. Ethylene application during a later storage stage showed an obvious accelerative effect on bulb sprouting, whereas ethylene application during the middle stage had no effect on sprouting. The biological progression of dormancy was further studied through cytological and physiological analyses. Under natural conditions, the ethylene level was reduced to trace amounts with the transition and progression of dormancy. A transient peak in ethylene release was found when the plugged plasmodesmata (PD) began to re-open and flower initiation began. The most common PD possessed electron-dense deposits in endo-dormancy. These data indicate that endo-dormancy ends when flower initiation begins and ethylene peak occurs. Ethylene application had no effect on dormancy release, while it hastened sprouting only after the release from endo-dormancy by high temperature.
冬季休眠在许多植物中得到了广泛的研究，而夏季休眠的信息则相对较少。中国水仙以其在年周期中经历的长时间夏季休眠而著称。在本研究中，我们对控制生长条件下休眠的性质进行了研究，并探讨了温度和乙烯对休眠解除的影响。即使在有利于生长的条件下，地上组织的生长停止和衰老也会发生，这表明存在一种内休眠过程。鳞茎在暴露于低温贮藏条件下无法发芽，而在低温贮藏前进行高温处理或在低温贮藏期间中断加热，则可使鳞茎发芽。这些结果表明，高温是内休眠解除的必要条件。在后期贮藏阶段施加乙烯对鳞茎发芽有明显的加速作用，而在中期施加乙烯对发芽则没有影响。通过细胞学和生理学分析进一步研究了休眠的生物学进程。在自然条件下，随着休眠的转变和进展，乙烯水平降低到痕量。当堵塞的胞间连丝（PD）开始重新打开并开始开花时，发现乙烯释放出现瞬时峰值。在内休眠中，最常见的 PD 具有电子致密沉积物。这些数据表明，当开花开始和乙烯峰出现时，内休眠结束。乙烯处理对内休眠的解除没有影响，而只有在高温解除内休眠后，它才会加速发芽。
