ATP-DEPENDENT AUXIN-INDUCED AND AUXINIC HERBICIDE-INDUCED VOLUME CHANGES IN ISOLATED PROTOPLAST SUSPENSIONS FROM SINAPIS-ARVENSIS L

Auxin- and auxinic herbicide-induced volume changes in enzymatically i solated protoplast suspensions from both auxinic herbicide-susceptible (S) and picloram-resistant (R) wild mustard (Sinapis arvensis L.) bio types were monitored by right-angle light scattering. The scattering p rofile of the volume change induced by IAA consisted of an initial shr inkage phase followed by swelling in both biotypes. Kinetic analysis o f the swelling phase indicated two first-order processes for the S pro toplasts, whereas a single first-order process was observed for the R. In the presence of picloram, only a swelling phase was observed for t he S protoplasts, whereas both shrinkage and swelling phases were obse rved in R protoplasts. When protoplasts from the R biotype were incuba ted with dicamba or MCPA, which are effective to varying degrees again st this biotype, the scattering profiles were similar to those observe d for the S biotype with picloram. Simultaneous incubation of R protop lasts with picloram and the calcium channel blocker verapamil reduced the initial shrinkage phase. The differences in response between R and S protoplasts to IAA and the auxinic herbicides at the cellular level suggest certain similarities with respect to the dynamics of protopla st volume changes and provide insight into auxin and auxinic herbicide action. (C) 1996 Academic Press.