Effects of external environmental factors on chromosome pairing in autotetraploid rye.

Effects of temperature and nitrogen on meiotic chromosome pairing in clones of autotetraploid rye were studied separately. Both experiments revealed that quadrivalents are highly sensitive to changes in environmental conditions. On the other hand, bivalent frequency in the PMC remained stable with temperature changes in spite of a significant decrease in chiasma frequency. With nitrogen stress, however, bivalent frequency in the PMC increased significantly. These results led to the conclusion that a bivalent formation is much more easily and efficiently accomplished than the formation of a multivalent. The underlying reasons for the greater stability of bivalents compared to multivalent configurations are discussed. The limitations of the improvement of meiotic behaviour of autotetraploids by increasing the quadrivalent frequency are also discussed.