Effect of PEG-treatment on the leaf growth response and auxin content in shoots of wheat seedlings

Addition of Polyethylene glycol(PEG) to the nutrient medium of wheatseedlings led to a rapid cessation of leaf growth and shrinkage, measured withahighly sensitive growth sensor, followed by a partial restoration of extensionin the subsequent 40 min. This osmotic shock resulted in IAAaccumulation in the shoots. Leaf extensibility, measured by addition of 5g as a counterweight to an extensiometer, did not change for 20min after the start of the treatment, but then increased andbecametwice as high as the initial value. Changes in leaf extensibility coincidedwitha restoration of leaf growth. Leaf shrinkage, which was observed immediatelyafter addition of the osmoticum, suggests that the initial growth response wasdue to a water deficit, which led to a decrease in cell turgor. Howeverrestoration of growth during water stress could be due to changes in cell wallrheological properties, which could be triggered by IAA accumulation.