Confirmation that abscisic acid accumulation is required for maize primary root elongation at low water potentials

Abstract

Previous work showed that primary root elongation in maize (Zeamays L.) seedlings at low water potentials was severely inhibited when accumulation of abscisic acid (ABA) was decreased using either fluridone or the vp5 mutant to inhibit carotenoid (and ABA) biosynthesis. The objective of this study was to confirm that the inhibition of root elongation resulting from these treatments was indeed attributable to the decrease in ABA levels. Seedlings were transplanted after germination to vermiculite at water potentials of −1.6 or − 0.3 MPa. ABA was mixed at various concentrations with the vermiculite to test whether the effects of fluridone and the vp5 mutation on root elongation could be overcome. In both treatments, restoration of ABA levels in the root apical 10 mm, which encompassed the elongation zone, resulted in recovery of root elongation rate at both −1.6 MPa and −0.3 MPa. Analysis of the spatial distribution of elongation rate showed that the recovery of overall root elongation resulted from restoration of the profile of elongation, and did not involve over-promotion of local elongation rate at any position. The recovery of root elongation was shown to be independent of effects of ABA status on shoot growth. When ABA was applied at high water potential, such that levels of ABA in the root tip reached those associated with maintenance of elongation at low water potentials, root elongation was inhibited. Thus, the response of root elongation to bulk tissue ABA content varied with the tissue water status. The results confirm that accumulation of ABA is required for the maintenance of maize primary root elongation at low water potentials.

Effects of varied water regimes on root length, dry matter partitioning and endogenous plant growth regulators in sunflower (Helianthus annuusL.)

“…The ABA was shown to inhibit shoot growth more than root growth (Saab et al 1990). Sharp et al (1994) also found a requirement of high ABA accumulation for maintenance of root elongation under low soil water potential. However, recent study showed that ABA has been found to inhibit the secondary root development as an adaptive response to the drought stress (Xiong et al 2006).…”

Interaction with ethylene: changing views on the role of abscisic acid in root and shoot growth responses to water stress

“…Increasing evidence indicates that this is not necessarily the case. Decreases in plant water status have been shown to change the compartmentation (Hartung, Radin & Hendrix 1988;Bacon, Wilkinson & Davies 1998), apparent sensitivity (Tardieu & Davies 1992;Dodd & Davies 1996) and response (Sharp et al . 1994) to ABA in various organs.…”

“…Initial studies used the fluridone and vp5 mutant approaches (Saab et al . 1990;Saab, Sharp & Pritchard 1992;Sharp et al . 1994).…”

Altered ABA, proline and hydrogen peroxide in an Arabidopsis glutamate:glyoxylate aminotransferase mutant

“…However, the involvement of other signals and how these other signals interact with the ABA signal remain unanswered questions. These questions arise, at least in part, from a number of observations that have shown that ABA applied to unstressed plants often does not elicit the same response as ABA accumulation that occurs under stress conditions (Sharp et al 1994;Imai et al 1995;Verslues and Bray 2006). Control of ABA accumulation and sensitivity also appears to involve extensive feedback regulation (Xiong et al 2002;Verslues and Bray 2006).…”