. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. IONIC CURRENTS AROUND PEA ROOT TIPS 57 ized in 6% (W/V) NaCIO for 5 min, rinsed four times in sterile dH:O, and aseptically germinated in petri dishes containing 1% agar in 'A strength modified Hoaglands solution ( mM MgSO4-7H:O: mM NaH:. PO4 • 2H2O; mMCa(NO,): • 4H2O; mM KNO3). Seeds were grown for 4 days at 20 ± 2°C in the dark. Seedlings bearing roots 20-30 mm in length were placed into petri dishes (9 cm diameter). Care was taken not to disturb the orientation of the root so as to avoid gravitropic pert
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. IONIC CURRENTS AROUND PEA ROOT TIPS 57 ized in 6% (W/V) NaCIO for 5 min, rinsed four times in sterile dH:O, and aseptically germinated in petri dishes containing 1% agar in 'A strength modified Hoaglands solution ( mM MgSO4-7H:O: mM NaH:. PO4 • 2H2O; mMCa(NO,): • 4H2O; mM KNO3). Seeds were grown for 4 days at 20 ± 2°C in the dark. Seedlings bearing roots 20-30 mm in length were placed into petri dishes (9 cm diameter). Care was taken not to disturb the orientation of the root so as to avoid gravitropic perturbations. A small perspex chamber (3 X 3 X 1 cm) was then positioned to enclose the root tip, which protruded into the center of the chamber via a hole slightly larger than the root, and sealed with white petroleum jelly, as in Figure la. Seedlings were then em- bedded in agar (1% in 'A Hoaglands solution as above), which was poured into the dish at 35°C. Within 15 min, the agar had solidified and the perspex chamber was re- moved, leaving a small well around the root tip. in which the measuring medium (sterile 'A Hoaglands solution) was placed (Fig. Ib). This preparation method ensured physical stability of the seedling throughout the measur- ing and wounding procedures. This physical stability was found to be crucial in order to obtain consistent current patterns. Seedlings were left in this position for 2 h before measurements were made. Submerging roots in the 'A Hoaglands solution did not affect root growth rate when examined after 2,24, and 48 hours (P > ; 1 -way anal- ysis of variance). Prior to a measurement, the petri dish containing the horizontally oriented pea root was placed on a gliding stage of an inverted microscope (Nikon Dia- phot) around which the vibrating probe was assembled. Roots were oriented horizontally during all experiments. Current measurements Extracellular currents were measured with a standard one dimensional vibrating probe (Jaffe
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
