Both Intact Microfilaments and Cortical Microtubules are Involved in the Maintenance of the Growth Rate of Internodal Cells of Nitellopsis

Abstract

: Automatic monitoring, with an eddy-current displacement transducer, treatments with CD and oryzalin separately, and with CD plus oryzalin in combination (CD = 10 mg/l, and oryzalin = 10 imol/l) were used to follow the elongation growth of internodal cells of Nitellopsis. These showed similar kinetics in inhibition and recovery tests. Inhibition to growth started about 10 to 15 min after treatment. However, complete inhibition to growth required 2 to 3 h. In contrast to inhibition, growth resumed quickly in the recovery test. Re-growth started after about 10 to 25 min, and recovered to a steady rate after 25 to 40 min following removal of the drugs. In the combined treatment, with only one drug removed, re-growth only occurred when the second drug was also removed. Cell turgor, hydraulic conductivity (Lp), and membrane potential (Em) were measured with the T-EP probe in the drug treatments. The possible involvement of changes in cell turgor, Lp and pH of walls and of cytoplasm in inhibition of growth were excluded. Disruption of MF and MT in internodal cells of Nitellopsis by CD and oryzalin were confirmed under laser-scanning confocal microscopy (Bio-Rad MRC-1024). The results showed that the maintenance of growth rate of internodal cells of Nitellopsis required both intact MF and MT.