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

In the culture of red beet hairy roots in shaking flasks, a period for accl imation without lateral root generation existed at the early stage, and the root tip meristems containing growing points (GPs) were found to be damage d under an elevated shear stress condition. The loading experiments of shea r stress to the hairy roots revealed that the GPs subjected to the acclimat ion 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 afte r culture for 50 h at 0.05 N/m(2) of shear stress were exposed to condition s at various levels of shear stress in a single column reactor, and a relat ively 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 hydrauli c stress and a second stage for 110 h at 1.0 N/m(2) of shear stress for act ive 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 roo ts did not undergo the first stage. (C) 2000 Elsevier Science S.A. All righ ts reserved.