Ascorbate Acid Increases Tolerance to Water Deficit Stress in Flowers of Cut Roses ( Rosa hybrida L. ) Caused by Enhanced Ascorbate Peroxidase Activity Effects of exogenous ascorbate acid on membrane protective system of in situ rice leaves under O3 stress Ascorbate Acid Increases Tolerance to Water Deficit Stress in Flowers of Cut Roses ( Rosa hybrida L. ) Caused by Enhanced Ascorbate Peroxidase Activity