The object of the present experiments was to see whether the concentration of antioxidants in lettuce leaves could be boosted by water stress. 'Baronet' lettuce plants were raised in growth chambers in a 12h photoperiod at day/night temperatures of 22 degsC/18 degsC.
In one treatment, water was withheld for just two days after six weeks of growth while in another water was withheld for four days four weeks after planting, then withheld for three days in the following week and for two days in the sixth week.
The concentration of antioxidants in well-watered plants was high when they were young but declined as they aged. If water was withheld, the concentration of antioxidants present at harvest was increased and the effect was the same whether water was withheld on three occasions or just once.
However, while the multiple-stress treatment significantly reduced crop growth, the single-stress treatment did not. Hence a mild water stress given shortly before harvest can further boost the health-giving properties of lettuce leaves.
Regulated Water Deficits Improve Phytochemical Concentration in Lettuce by Oh, Carey and Rajashekar (2010). Journal of the American Society for Horticultural Science 135 (3): 223-229. Members of ISHS can view the Journal of the American Society for Horticultural Science from the website www.ishs.org.