To elucidate the role of aquaporins in the control of the root pressure, we tested the effects of HgCl2 (aquaporin blocker) at concentrations from 10−8 to 10−2 M on the exudation rate (J w). Experiments were performed with detached roots of 5–7-day-old etiolated maize (Zea mays L.) seedlings. HgCl2 suppressed exudation by 50–70% at the concentration of 2 × 10−5 M. At the concentration of 2.5 × 10−4 M, HgCl2 reduced J w during first 20–40 min, but in 2 h, it activated exudation by ten and more times. In this case, the root and osmotic pressures of the exudates increased by 1.5 times. The hydraulic conductance reduced approximately by 30% during first 30 min and increased severalfold in 2 h. The temperature coefficient (Q10) of J w attained 14 in 2 h. At the concentration of 10−2 M, HgCl2-induced acceleration of exudation was replaced by its inhibition essentially immediately. We suggested that a driving force for HgCl2-induced stimulation of the J w might be an increase in the osmotic component of the root pressure or the involvement of its nonosmotic (so-called metabolic) component. The results allow a supposition that aquaporins are involved in the control of water transport in the root.
Russian Journal of Plant Physiology – Springer Journals
Published: Oct 31, 2008
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