| 15235000 |
Melkonian J, Yu LX, Setter TL: Chilling responses of maize (Zea mays L.) seedlings: root hydraulic conductance, abscisic acid, and stomatal conductance. J Exp Bot. 2004 Aug;55(403):1751-60. Epub 2004 Jul 2.
Maize seedling water relations and abscisic acid (ABA) levels were measured over 24 h of root chilling (5.5 degrees C). At 2.5 h into chilling, leaf ABA levels increased by 40x and stomatal conductance (g (s)) decreased to 20% compared with prechill levels. Despite a rapid g (s) response to root chilling, leaf water potential (Psi (L)) of chilled seedlings decreased to -2.2 MPa resulting in a complete loss of turgor potential (psi (p)). Ineffective g (s) control early in chilling resulted from decreased root hydraulic conductance (L (r)) due to increased water viscosity and factor (s) intrinsic to the roots. After 24 h chilling, Psi (L) and psi (p) of chilled seedlings recovered to control levels due to stomatal control of transpiration and increased L (r). The impact of the temporal changes in g (s) and L (r) on maize seedling water relations during chilling was analysed using a simple, quantitative hydraulic model. It was determined that g (s) is critical to stabilizing Psi (L) at non-lethal levels in chilled seedlings at 2.5 h and 24 h chilling. However, there was also a significant contribution due to increased L (r) at 24 h chilling so that psi (p) increased to control levels. As a first step in determining the factor (s) responsible for the increase in L (r), cDNA microarrays were used to quantify the transcript levels of eight aquaporins obtained from mature root tissue at 24 h chilling. None of these were significantly up-regulated, suggesting that the increase in L (r) was not due to regulation of these aquaporins at the transcriptional level. |
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