Accurate and speedy measurement of cell growth and assessment of growth-related bioprocess kinetics are essential to the efficient and rational development of plant cell bioprocess engineering. Accurate measurement of cell growth in a plant cell bioreactor system has been a serious problem, in large part, due to the morphology and variation of plant cell lines, such as embryo cells, hairy root cells, and aggregated cells.Based on our studies, we have concluded that the conductivity method of measuring growth kinetics of plant cell lines was the method of choice, especially for the purpose of bioprocess engineering application of plant cell cultures. The major advantages of using conductometry as the biosensing technique for measurement of plant cell growth kinetics are:(1) The method is very economical and efficient and gives accurate, reliable, and reproducible measurements, while amenable to continuous on-line monitoring and process control. (2) It is a noninvasive method which does not adversely affect the plant cells or the bioreactor operation. (3) The kind of plant cell lines or their morphology do not affect the method itself.For the development of plant cell culture technology, accurate and rapid measurement of cell growth and assessment of growth-related bioprocess kinetics are essential to the rational development of plant cell bioprocess engineering. Although the plant cell culture system appears to be similar to a microbial cell culture system, there are important differences between the two, and the best method of assessing the plant cell growth kinetics should be carefully examined and evaluated. The major differences include cell size, aggregation of plant cells, change in plant cell physiology for its primary and secondary metabolisms, rheological properties of the medium, and requirement of plant cells for complex nutrients.Measurement of cell growth in plant cell cultivation devices presents a serious problem in some cases. There are various plant cell lines and cell morphology that con- tribute to this problem. There are embryo cells, hairy root cells, aggregated cells, and others that are employed in plant cell culture systems for varying purposes. In each case the determination of growth rate requires different methodology.There are several methods of evaluating growth kinetics of plant cells. Selected examples include fresh cell weight, settled volume, packed cell volume, cell optical d e n~i t y ,~-~ cell size and n~m b e r ,~ nitrogen protein c~n t e n t ,~,~~-~~ nucleic acid,11*'3-'6 organic matters," mitotic index, I4 electrical r e~p i r a t i o n ,~~"~~~ and pH measurement.2' In addition, concentrations of substrate and extracellular product have also been used for such a purpose of selecting the best method of studying growth kinetics, especially from the bioprocess engineering point of view.In our study, several methods that could be used for evaluation of plant cell growth kinetics were compared using the same cell line (Pyrus communis L) medium. Based on this study, the method tha...