JXB Advance Access originally published online on January 12, 2006
Journal of Experimental Botany 2006 57(3):655-664; doi:10.1093/jxb/erj055
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
RESEARCH PAPER |
Water uptake by roots of Hordeum marinum: formation of a barrier to radial O2 loss does not affect root hydraulic conductivity
1School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Crawley 6009, Western Australia
2CRC for Plant-Based Management of Dryland Salinity, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Crawley 6009, Western Australia
3Lehrstuhl für Pflanzenoekologie, Universitaet Bayreuth, D-95440 Bayreuth, Germany
* To whom correspondence should be addressed. E-mail: tdcolmer{at}cyllene.uwa.edu.au
The adventitious roots of Hordeum marinum grown in stagnant deoxygenated solution contain a barrier to radial O2 loss (ROL) in basal zones, whereas roots of plants grown in aerated solution do not. The present experiments assessed whether induction of the barrier to ROL influences root hydraulic conductivity (Lpr). Wheat (Triticum aestivum) was also studied since, like H. marinum, this species forms aerenchyma in stagnant conditions, but does not form a barrier to ROL. Plants were grown in either aerated or stagnant, deoxygenated nutrient solution for 21–28 d. Root-sleeving O2 electrodes were used to assess patterns of ROL along adventitious roots, and a root-pressure probe and a pressure chamber to measure Lpr for individual adventitious roots and whole root systems, respectively. Lpr, measured under a hydrostatic pressure gradient, was 1.8-fold higher for individual roots, and 5.6-fold higher for whole roots systems, in T. aestivum than H. marinum. However, there was no difference in Lpr between the two species when measured under an osmotic driving force, when water moved from cell to cell rather than apoplastically. Root-zone O2 treatments during growth had no effect on Lpr for either species (measured in aerobic solution). It is concluded that induction of the barrier to ROL in H. marinum did not significantly affect the hydraulic conductivity of either individual adventitious roots or of the whole root system.
Key words: Adventitious roots, aerenchyma, exodermis, hydraulic conductivity, hypodermis, O2-deficiency, pressure chamber, radial O2 loss, root pressure probe, Triticum aestivum, wheat