Cell Cycle Plasticity in Response of Low Temperature in Root Tips of TetraploidMedicago

Flow-cytometric analysis was carried out to determine the effect of low temperature on the changes in proportion of 2C:4C complement of DNA in root cells from three different zones (meristem apex, elongation and differentiation) in seedlings of Medicago sativa cv. Sitel. 2C:4C complement of DNA in cells were estimated after the treatments of the roots at control temperature of24°C, elevated temperatures of26°C, 30°C, 37°C and low temperatures—10°C and 5°C (in three different periods of duration 15, 38, 45 days). The observed results showed that at control temperature percentage of nuclei 2C:4C in meristem apex is 65:35, in elongation zone 50:50 and in differentiation zone is 40:60. The elevated temperatures (26°C, 30°C, 37°C) influenced this proportion very slightly while treatments of roots with low temperature especially in a period of 45 days changed 2C:4C complement of DNA drastically. It was found that root treated for 45 days at temperature of 10°C the 2C:4C in meristem apex is 78:22, elonga...