Effects of high osmotic potential of a medium on mitotic cycle in roots ofVicia faba L

The present paper deals with the effects of osmotic potential of a medium on cell reproduction and elongation of the roots ofVicia faba L. andVicia sativa L. As the osmoticum polyethylene glycol (PEG 4000) in various concentrations ranging from 5 % to 25 % (i.e. fromca.-0.11 up to -1.27 MPa) has been used. The results show that at higher concentrations than 7.5 %, the growth of roots is slowed down and at the concentration of 25 % PEG this decrease in growth rate is as much as 6 fold compared with the control. The mitotic cycle is prolonged, however, only 1.86 times. Thus, the inhibition of root growth is caused mainly by the inhibition of cell elongation. Concerning the effect of high osmotic potential on mitotic cycle it was found that the roots after immersion into 25% PEG are able to overcome this osmotic stress and after 6 h to renew the mitotic activity. The S phase of the cycle is the most sensitive to this factor and even after mitotic activity was renewed it showed a slower rate in comparison with the control.