关键词: 烟草, 花粉, 低温处理, 超微结构, 细胞编程死亡

Abstract: The degenerate characteristics, including morphological, structural and vigorous changes of tobacco pollens were studied following different durations of cold treatment at 4℃ by using light and electronic microscopy, as well as TTC (triphenyltetrazolium chloride) assay. The following results were obtained: (1) After cold treatment, some of the pollens became empty and the cytoplasm of those pollens shrank. The longer the cold treatment lasted, the higher frequency of the degenerate pollens could be detected. (2) The degeneration of pollens was also detected at ultrastructural level. However, ultrastructural changes did not occurred synchronously with the duration of the treatment. Usually, dictyosomes and plastids degenerated first, followed by mitochondria and then the nucleus. During the process of the degeneration, vacuoles and endoplasmic reticulum (ER) played an important role. Vacuoles eroded and digested the surrounding cytoplasm gradually by partial or whole disappearance of tonoplasts. The proliferation of ER occurred as the time of the treatment increased. Simultaneously, the cisternae of ER became bulged, engulfing the cytoplasmic components. Finally, the cytoplasm shrank and converted into a dark disorganized mass when the pollen died. (3) Frequency of the vigorous pollens was detected by the TTC assay. It was shown that the frequency of the vigorous pollens decreased as the cold treatment went on. After 20 days of treatment, almost all the pollens lost their vigor. As a result, the degeneration of cold treated tobacco pollens occurred gradually and increasingly. It was PCD.

Key words: tobacoo, pollen, cold treatment, ultrastructure, programmed cell death