Decrease in membrane hydraulic conductance of rhizodermal cells under nitrate deficit is related to acidification at the root surface

Decrease in membrane hydraulic conductance of rhizodermal cells under nitrate deficit is related... Barley seedlings (Hordeum vulgare L.) were grown on porous plates submerged in Knop medium at pH 6.0 (control) and in a similar nutrient solution where NO 3 − was replaced with Cl− (treatment); in some treatments Mes buffer (10–20 mM, pH 6.0) was added to the medium. In the absence of buffer, the pH of the medium shifted towards the alkaline region in the presence of NO 3 − and to the acidic region in the presence of Cl−, with the total shift of no more than 0.3 pH units per day. The replacement of NO 3 − with Cl− (in a buffer-free medium) decreased the hydraulic membrane conductance of rhizodermal cells (L p) within a 4-h period; after one day L p settled at approximately 50% of its initial value observed in untreated plants. When the removal of nitrate from the medium was accompanied by the addition of buffer, no changes in L p were observed over a 1-day period. The perfusion of external solution (at a rate of 10 mm/s) made it possible to control pH in the proximity to root surface (pHs). These experiments showed that L p was independent of the surface pH in the pHs range 7.0–5.0, whereas at pHs = 4.5 L p decreased within 15 min to a steady-state level of about 50% of the control value. It is concluded that the reduction of L p under nitrate deficit was related to acidification of the medium near the root surface. The acidic pH shift could be caused by the cessation of proton/nitrate symport and by activation of the plasmalemma H+-pump, related to changes in the cytosolic pH-stat. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Russian Journal of Plant Physiology Springer Journals

Decrease in membrane hydraulic conductance of rhizodermal cells under nitrate deficit is related to acidification at the root surface

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Publisher
SP MAIK Nauka/Interperiodica
Copyright
Copyright © 2008 by MAIK Nauka
Subject
Life Sciences; Plant Sciences ; Plant Physiology
ISSN
1021-4437
eISSN
1608-3407
D.O.I.
10.1134/S1021443708050051
Publisher site
See Article on Publisher Site

Abstract

Barley seedlings (Hordeum vulgare L.) were grown on porous plates submerged in Knop medium at pH 6.0 (control) and in a similar nutrient solution where NO 3 − was replaced with Cl− (treatment); in some treatments Mes buffer (10–20 mM, pH 6.0) was added to the medium. In the absence of buffer, the pH of the medium shifted towards the alkaline region in the presence of NO 3 − and to the acidic region in the presence of Cl−, with the total shift of no more than 0.3 pH units per day. The replacement of NO 3 − with Cl− (in a buffer-free medium) decreased the hydraulic membrane conductance of rhizodermal cells (L p) within a 4-h period; after one day L p settled at approximately 50% of its initial value observed in untreated plants. When the removal of nitrate from the medium was accompanied by the addition of buffer, no changes in L p were observed over a 1-day period. The perfusion of external solution (at a rate of 10 mm/s) made it possible to control pH in the proximity to root surface (pHs). These experiments showed that L p was independent of the surface pH in the pHs range 7.0–5.0, whereas at pHs = 4.5 L p decreased within 15 min to a steady-state level of about 50% of the control value. It is concluded that the reduction of L p under nitrate deficit was related to acidification of the medium near the root surface. The acidic pH shift could be caused by the cessation of proton/nitrate symport and by activation of the plasmalemma H+-pump, related to changes in the cytosolic pH-stat.

Journal

Russian Journal of Plant PhysiologySpringer Journals

Published: Aug 30, 2008

References

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