A study on the temperature response of pollen mother cells in Norway spruce

The effect of temperature upon the pattern of meiotic development was studied in PMC in Picea abies. The twigs were collected from grafts and exposed to different temperature conditions in a climatic cabinet. (The thermoperiods used were + 20°Cl + 15°C and + 15°C/+ 10°C respectively.) The rate as well as the temperature sum requirement of the development within given limits were compared. The data obtained are compiled in Figure 31. Significant differences obtained in some instances indicate that at least some phases of development are accelerated by a rise in the temperature. However, the results were somewhat contradictory with respect to different phases of the meiotic development. For example a shorter time and a smaller temperature sum were needed for the development from diplotene to interkinesis (compared at the 50 per cent level) in the experiment carried out at the higher temperature. On the other hand, the reaching of tetrads proceeded faster and had a lower ternperature sum requirement in the lower temperature conditions. The exposure of the material to - 5O°C caused a delay in the meiotic development. Furthermore, the induction of irregularities in PMC following the treatment at - 5°C was studied. Data on the frequency of different types of irregularity, the frequency of irregularities at different meiotic stages as well as the relationship between the occurrence of sensitive stages during the treatment at - 5°C and the frequency of irregularities were presented. The relationships between the origin of the material on the one hand and the pattern of meiotic development or the frequency of irregularities induced on the other hand were discussed