PLANT PHYSIOLOGY , Vol 113, Issue 2 595-602, Copyright © 1997 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Water Transport Properties of Roots and Root Cortical Cells in Proton- and Al-Stressed Maize Varieties
B. Gunse, C. Poschenrieder and J. Barcelo
Laboratorio de Fisiologia Vegetal, Facultad de Ciencias, Universidad Autonoma de Barcelona, E-08193 Bellaterra Spain
Root and root cell pressure-probe techniques were used to investigate the
possible relationship between Al- or H+-induced alterations of the
hydraulic conductivity of root cells (LPc) and whole-root water
conductivity (LPr) in maize (Zea mays L.) plants. To distinguish between H+
and Al effects two varieties that differ in H+ and Al tolerance were
assayed. Based on root elongation rates after 24 h in nutrient solution of
pH 6.0, pH 4.5, or pH 4.5 plus 50 [mu]M Al, the variety Adour 250 was found
to be H+-sensitive and Al-tolerant, whereas the variety BR 201 F was found
to be H+-tolerant but Al-sensitive. No Al-induced decrease of root pressure
and root cell turgor was observed in Al-sensitive BR 201 F, indicating that
Al toxicity did not cause a general breakdown of membrane integrity and
that ion pumping to the stele was maintained. Al reduced LPc more than LPr
in Al-sensitive BR 201 F. Proton toxicity in Adour 250 affected LPr more
than LPc. In this Al-tolerant variety LPc was increased by Al.
Nevertheless, this positive effect on LPc did not render higher LPr values.
In conclusion, there were no direct relationships between Al- or H+-induced
decreases of LPr and the effects on LPc. To our knowledge, this is the
first time that the influence of H+ and Al on root and root cell water
relations has been directly measured by pressure-probe techniques.
