17 research outputs found
Recommended from our members
Growth of Arabidopsis Thaliana Seedlings Under Water Deficit Studied by Control of Water Potential in Nutrient-Agar Media
We have characterized the growth responses of Arabidopsis thaliana seedlings to water deficit. To manipulate the water potential, we developed a method whereby the nutrientâagar medium could be supplemented with polyethylene glycol (PEG 8000); PEG was introduced into gelled media by diffusion, which produced media with water potential as low as â1.6âMPa. For darkâgrown plants, hypocotyl growth had a hyperbolic dependence on water potential, and was virtually stopped by â1âMPa. In contrast, primary root elongation was stimulated by moderate deficit and even at â1.6âMPa was not significantly less than the control. That these results did not depend on a direct effect of PEG was attested by obtaining indistinguishable results when a dialysis membrane impermeable to PEG was placed between the medium and the seedlings. For lightâgrown seedlings, moderate deficit also stimulated primary root elongation and severe deficit reduced elongation only partially. These changes in elongation were paralleled by changes in root system dry weight. At moderate deficit, lateral root elongation and initiation were unaffected and at higher stress levels both were inhibited. Primary root diameter increased steadily with time in wellâwatered controls and under water deficit increased transiently before stabilizing at a diameter that was inversely proportional to the deficit. Along with stimulated primary root elongation, moderate water deficit also stimulated the rate of cell production. Thus, A. thaliana responds to water deficit vigorously, which enhances its use as a model to uncover mechanisms underlying plant responses to water deficit
The relationship between leaf growth and ABA accumulation in the grass leaf elongation zone.
Detached barley (Hordeum vulgare L.) shoots, maintained at different air temperatures and VPDs, were fed ABA via the sub-crown internode in a leaf elongation assay. Analysis of variance of leaf elongation rate (LER) showed significant effects of temperature (T), fed [ABA] and the interaction T Ă [ABA]. However, the interaction became non-significant when LER was modelled against the [ABA] of the elongation zone, [EZ-ABA] When detached barley shoots were fed sap from droughted maize (Zea mays L.) plants, sap [ABA] could not explain the growth inhibitory activity. Measurement of [EZ-ABA] accounted for this 'unexplained' growth inhibition. The detached shoot experiments indicated that [EZ-ABA], and not xylem sap [ABA], was an appropriate explanatory variable to measure in droughted plants. However, ABA accumulation in the elongation zone could not explain a 35% growth reduction in intact droughted plants; thus we considered an interaction of water status and ABA. Using a coleoptile growth assay, we applied mild osmotic stresses (Ï=0 to â0.06 MPa) and 10â4 mol mâ3 ABA. Individually, these treatments did not inhibit growth. However, osmotic stress and ABA applied together significantly reduced growth. This interaction may be an important mechanism in explaining leaf growth inhibition of droughted plants