Effect of root-zone temperature on growth and water uptake by lettuce plants in solution culture

Butterhead lettuce plants cv. "Tardisix" were grown with the nutrient film technique (NFT) in an unheated glasshouse under three different solution temperature regimes (10-15-20 degrees C). Cumulative water uptake (1/plant) increased with increasing solution temperature (2.84, 4.79, and 6.74 respectively). Shoot fresh and dry weights (g/plant) increased significantly with temperature (122.5, 228.1, 275.3 and 7.2, 13.7, 13.8 respectively), while the opposite was found for dry root weight (4.3, 2.5, 2.2 g/plant). The average number of leaves per plant increased significantly with increasing solution temperature (21.6, 25.7, and 35.7), as well as the mean percentage of shoot water content (95.1, 96.5, 97.2). Shoot nitrate content was not affected by solution temperature, being always relatively low (up to 935 mgNO(3),-N/kg fresh shoot weight).