Cytological mechanism of pollen abortion induced by high temperature in Populus canescens

  Objective  The effects of high temperature on microsporogenisis and cytological mechanism of pollen abortion induced by high temperature were conducted in P. canescens, aiming at improving the technology of forest triploid breeding though inducing gamete chromosme doubling by high temperature.

  Method  In this study, the effects of high temperature, meiotic stage and duration on percentage of aborted pollen were conducted after male flower buds being exposed to 38 ℃ for 3 or 6 h in P. canescens. Subsequently, the differences in chromosome behaviour, meiotic microtubule cytoskeleton and development of tapetum between untreated pollen mother cells (PMCs) and treated PMCs were studied to reveal the cytological mechanism of aborted pollen production induced by high temperature.

  Result  (1) Meiotic stages, temperature, duration, meiotic stage × temperature interactions and meiotic stage × duration interactions had significant effects on percentage of aborted pollen. The highest percentage of aborted pollen was (25.11 ± 4.28)% when PMCs were treated with 41 ℃ for 3 h at metaphase Ⅰ. (2) Compared with PMCs in the control group, meiotic microtubule cytoskeleton was depolymerized and some spindles were lost within the PMCs at metaphase Ⅰ and Ⅱ, leading to the abnormal chromosome segregation at anaphase Ⅰ and Ⅱ and forming a great number of lagging chromosomes. These lagging chromosomes were retained within cytoplasm, causing some micronuclei to form. Therefore, aborted pollen formed due to the formation of polyads at tetrad stage. (3) Although high temperature could also delay the degradation of the tapetum, the anthers normally dehisced and pollen grains were released. Thus, the delayed degradation of the tapetum was not responsible for the formation of aborted pollen.

  Conclusion  After male flower buds being treated by 38 ℃ for 3 or 6 h, some spindles are lost within the PMCs at metaphase Ⅰ and Ⅱ, leading to form a great number of lagging chromosomes and polyads, which is the cytological mechanism of aborted pollen formation induced by high temperature.