Culture of red beet hairy roots by considering variation in sensitivity of tip meristems to hydraulic stress

In the culture of red beet hairy roots in shaking flasks, a period for acclimation without lateral root generation existed at the early stage, and the root tip meristems containing growing points (GPs) were found to be damaged under an elevated shear stress condition. The loading experiments of shear stress to the hairy roots revealed that the GPs subjected to the acclimation acquired tolerance to shear stress, retaining relatively high viability of GPs up to 0.6 N/m(2) of loaded shear stress. Next, the hairy roots after culture for 50 h at 0.05 N/m(2) of shear stress were exposed to conditions at various levels of shear stress in a single column reactor, and a relatively high growth rate was obtained in the vicinity of 1.0 N/m(2) of shear stress. According to these results, two-stage cultures of hairy roots were then performed, which was comprised of a first stage for 50 h at 0.05 N/m(2) of shear stress for the prevention of decay of the GPs caused by hydraulic stress and a second stage for 110 h at 1.0 N/m(2) of shear stress for active elongation of the GPs with sufficient nutrient supply by regulation of the medium flow rate, The cell concentration ultimately reached 7.6 kg dry cells/m(3), although no growth was observed in the case where the hairy roots did not undergo the first stage. (C) 2000 Elsevier Science S.A. All rights reserved.