Nutritional Requirements for Polyploid Mitoses in Cultured Pea Root Segments

AbstractDiploid and polyploid mitoses could be stimulated in excised segments of the mature region of pea roots grown on a sterile culture medium. Diploid mitoses were observed in segments cultured on water alone for 72 hours. Their frequency was increased by the presence of salts, sucrose, vitamins, and any two or all three of the following: an amino mixture, auxins, and kinetin.Polyploid mitoses were observed 72 hours after the beginning of the culture period in segments cultured on salts, sucrose, vitamins, auxins, and kinetin. Polyploid mitoses required the presence of auxins and kinetin in the culture medium. Their frequency was not affected by the presence of a reduced nitrogen source. Light treatments had no effect on the frequency of diploid or polyploid mitoses.Diploid mitoses were first observed about 24 hours after the beginning of the culture and their frequency increased thereafter. Experiments with colchicine showed that diploid cells were entering mitosis for the first time as late as 60 hours after the beginning of the culture.Polyploid mitoses showed a long lag time when compared with diploid mitoses. They began at about 60 hours and their frequency increased thereafter. Experiments with colchicine showed that polyploid cells were entering mitosis for the first time as late as 84 hours after the beginning of the culture.The presence of kinetin in the medium was not required during the first 24 hours in culture for the appearance of polyploid mitoses at 74 hours. However, the presence of kinetin was required after 24 hours. Auxin was required at some time during the first 24 hours of the culture and its continuous presence may be required for the stimulation of polyploid mitoses.