Yamada Tetsuya, Ichimura Kazuo, van Doorn Wouter G
National Institute of Floricultural Science, 305-8519 Ibaraki, Japan.
Planta. 2007 Oct;226(5):1195-205. doi: 10.1007/s00425-007-0566-3. Epub 2007 Jul 6.
Depending on the species, the end of flower life span is characterized by petal wilting or by abscission of petals that are still fully turgid. Wilting at the end of petal life is due to programmed cell death (PCD). It is not known whether the abscission of turgid petals is preceded by PCD. We studied some parameters that indicate PCD: chromatin condensation, a decrease in nuclear diameter, DNA fragmentation, and DNA content per nucleus, using Prunus yedoensis and Delphinium belladonna which both show abscission of turgid petals at the end of floral life. No DNA degradation, no chromatin condensation, and no change in nuclear volume was observed in P. yedoensis petals, prior to abscission. In abscising D. belladonna petals, in contrast, considerable DNA degradation was found, chromatin was condensed and the nuclear volume considerably reduced. Following abscission, the nuclear area in both species drastically increased, and the chromatin became unevenly distributed. Similar chromatin changes were observed after dehydration (24 h at 60 degrees C) of petals severed at the time of flower opening, and in dehydrated petals of Ipomoea nil and Petunia hybrida, severed at the time of flower opening. In these flowers the petal life span is terminated by wilting rather than abscission. It is concluded that the abscission of turgid petals in D. belladonna was preceded by a number of PCD indicators, whereas no such evidence for PCD was found at the time of P. yedoensis petal abscission. Dehydration of the petal cells, after abscission, was associated with a remarkable nuclear morphology which was also found in younger petals subjected to dehydration. This nuclear morphology has apparently not been described previously, for any organism.
根据物种的不同，花朵寿命结束时的特征表现为花瓣枯萎或仍完全膨压的花瓣脱落。花瓣寿命结束时的枯萎是由程序性细胞死亡（PCD）导致的。目前尚不清楚膨压花瓣的脱落是否先于PCD。我们研究了一些指示PCD的参数：染色质凝聚、核直径减小、DNA片段化以及每个细胞核的DNA含量，使用的是东京樱花和颠茄，它们在花期结束时均表现出膨压花瓣的脱落。在脱落之前，东京樱花花瓣中未观察到DNA降解、染色质凝聚以及核体积的变化。相比之下，在脱落的颠茄花瓣中，发现了大量的DNA降解，染色质凝聚且核体积大幅减小。脱落后，两个物种的核面积都急剧增加，并且染色质分布变得不均匀。在开花时切断的花瓣经脱水处理（60摄氏度下24小时）后，以及在开花时切断的圆叶牵牛和矮牵牛的脱水花瓣中，观察到了类似的染色质变化。在这些花朵中，花瓣寿命通过枯萎而非脱落终止。得出的结论是，颠茄中膨压花瓣的脱落之前有许多PCD指标，而在东京樱花花瓣脱落时未发现此类PCD证据。脱落后花瓣细胞的脱水与一种显著的核形态相关，这种核形态在经历脱水的较年轻花瓣中也能发现。显然，此前尚未针对任何生物体描述过这种核形态。
