JXB Advance Access originally published online on March 26, 2004
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Journal of Experimental Botany, Vol. 55, No. 399, pp. 1115-1123, May 1, 2004
© 2004 Oxford University Press
Plants and the Environment |
Rapid and tissue-specific changes in ABA and in growth rate in response to salinity in barley leaves
Received 7 January 2004; Accepted 21 January 2004
1 Division of Biological Sciences, University of Paisley, Paisley PA1 2BE, Scotland, UK
2 Ufa Research Centre, Russian Academy of Sciences, 450054 Ufa, Russia
* To whom correspondence should be addressed. Fax: +44 (0)141 848 3663. E-mail: fric-bs0{at}wpmail.paisley.ac.uk
The addition of 100 mM NaCl to the root medium of barley plants caused the rapid cessation of elongation of the growing leaf three, followed by a sudden resumption of growth during the following hour. The idea that resumption of growth is preceded and mediated by rapid and tissue-specific changes in ABA concentration and by changes in transpiration was tested. Leaf elongation velocity was recorded continuously using linear variable displacement transducers (LVDT), ABA was determined by immunoassay, and transpiration and stomatal conductivity were measured gravimetrically and by porometry, respectively. Within 10 min following addition of salt, ABA increased 6-fold in the distal portion of the leaf elongation zone; in the proximal portion, ABA accumulated with a delay. In the portion of the growing blade that had emerged ABA increased 3-fold and remained elevated during the following 20 min. This preceded a decrease in transpiration and stomatal conductivity, which, in turn, coincided with growth resumption. Twenty hours following the addition of salt, the ABA concentrations had returned to the level before stress. Leaf elongation velocity was still reduced. It is concluded that NaCl causes a rapid increase in ABA in the transpiring portion of the growing leaf. This leads to a decrease in transpiration. As a result, xylem water potential is expected to rise. The moment that the water potential gradient between the xylem and the peripheral cells in the growth zone favours water uptake again into the latter, leaf elongation resumes. The results suggest that ABA causes different responses in different leaf regions, all aimed at promoting the resumption of leaf growth.
Key words: Abscisic acid, cell elongation, Hordeum vulgare, leaf growth, salinity, water relations.
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