Abstract
Leaf lettuce (Lactuca sativa L. cv. Greenwave) was grown in combinatory environments of electric conductivity (EC) of nutrient solution and photosynthetic photon flux (PPF) to investigate their influence on fresh weight and leaf area in plantlet and fresh weight of leaf at harvest. The experiments were conducted under the combinations of three levels of EC, of 1.0, 2.0 dS m−1 and tap water and three levels of PPF of 50, 100 and 150 μmol m−2 s−1 to examine fresh weight and leaf area of plantlet. Although PPF had no influence on fresh weight grown in tap water, fresh weight significantly increased as PPF increased in nutrient solution of EC 1.0 and 2.0 dS m−1. Leaf area cultured in tap water decreased as PPF increased, however leaf area greatly increased as PPF increased in nutrient solution of EC 1.0 and 2.0 dS m−1. Plantlet grown under two levels of nutrient solution as tap water and EC 1.0 dS m−1 and three levels of PPF 50, 100 and 150 μmol m−2 s−1 were transplanted to hydroponic system with EC 2.0 dS m−1, PPF 200 μmol m−2 s−1, photoperiod 14 h and temperature 24°C to investigate the effect of condition at germination and raising seedling stages on fresh weight at harvest. Fresh weight of leaf lettuce showed similar tendency as fresh weight of plantlet, and it was found that EC of nutrient solution and PPF at the stage of germination and raising seedling significantly influenced fresh weight at harvest.
