Nutritional quality, mineral and antioxidant content in lettuce affected by interaction of light intensity and...

Light and nutrient are important factors for vegetable production in plant factory or greenhouse. The total 12 treatments which contained the combination of four light intensity (150, 250, 350 and 450 μmol · m^-2 · s^-1) and three nutrient solution concentration (NSC) (1/4, 1/2, 3/4 strength NSC) were established for investigation of lettuce growth and quality in a growth chamber. The combination of light intensity and NSC exhibited significant effects on photosynthetic pigment, nutritional quality, mineral content and antioxidant capacity. That a higher light intensity were readily accessible to higher chlorophyll a/b showed in lettuce of treatment of 350 μmol · m^-2 · s^-1 × 3/4NSC and 450 μmol · m^-2 · s^-1 × 1/4NSC. Lower total N contents, higher content of soluble protein, vitamin C, soluble sugar and free amino acid exhibited in lettuce under treatment of 250 and 350 μmol · m^-2 · s^-1 × 1/4NSC or 3/4NSC. With increasing NSC and LED irradiance, the content of total P and K in lettuce increased and decreased, respectively. The highest and lowest total Ca content were found in treatment of 150 μmol · m^-2 · s^-1 × 1/4NSC and 450 μmol · m^-2 · s^-1 × 1/4NSC, respectively, and higher content of total Mg and Zn was observed under 250 μmol m^-2 s^-1 × 1/4NSC and 150 μmol · m^-2 · s^-1 × 3/4NSC, respectively. The antioxidant contents generally decreased with increasing NSC level. The higher antioxidant content and capacity occurred in lettuce of 350 μmol · m^-2 · s^-1 × 1/4NSC treatment. The interaction of 350 μmol · m^-2 · s^-1 × 1/4NSC might be the optimal condition for lettuce growth in plant factory.