Effects of nutrient solution electrical conductivity and sulfur, magnesium, and phosphorus concentration on sesquiterpene lactones in hydroponically grown lettuce (Lactuca sativa L.)
2009
Seo, Myeong Whoon | Yang, Dong Sik | Kays, Stanley J. | Kim, Jun-Hong | Woo, Jin Ho | Park, Kuen Woo
The effect of nutrient solution electrical conductivity (EC) and sulfur (S), magnesium (Mg), and phosphorus (P) levels on the content of the primary sesquiterpene lactones (SLs), lactucin, 8-deoxylactucin, and lactucopicrin, in hydroponically grown lettuce was assessed. Lettuce grown at 4 EC levels (0.5, 1.0, 2.0, and 3.0dSm⁻¹) displayed significant differences in leaf area index, number of leaves, plant height, fresh weight per plant, and chlorophyll content that were highest at EC 2.0dSm⁻¹. Lactucin (5.5μgg⁻¹ dry weight), 8-deoxylactucin (7.5), lactucopicrin (35.8), and total SLs (48.7) concentraions were highest at EC 0.5dSm⁻¹. Four S (8, 16, 48, and 80mgL⁻¹) and Mg (6, 12, 36, and 60mgL⁻¹) levels and 3 P (8, 16, and 48mgL⁻¹) levels were assessed for their effect on individual and total SLs. S and P had the greatest effect on SL levels. Plants in the lowest S level had significantly higher lactucin, lactucopicrin and total SLs. Each of the SLs was higher in the highest P level while Mg influenced only the lactucopicrin level in a quadratic manner. The results indicate that solution culture conditions can strongly influence the SL concentration and therefore bitterness and acceptability of lettuce.
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