at intervals of one month using aseptic procedures, remove small samples of callus from culture growing....... , close the culture tube immediately after this manipulation. place these samples, individually into patri dishes containing 10 ml of liquid "" medium and stir gently with a glass rods until the cells float apart.
this treatment separates the different stages of embryos development.
observers the suspension of cells with a binocular microscope or an inverted microscope.
if 'old' callus which has lost the ability to undergo embryogenesis in not available, younger culture (12 weeks after the isolation of the carrot explants) can be form embryos on ........ , but not on ....., . therefore only the treatments in part B of Fig. 7.2 will provide clear cut results.