In horticultural production substrates have been sought that would ensure the optimum physical conditions (including aerobic and aquatic) in the root environment. The soil substrate can be modified with synthetic supplements called hydrogels or sorbents. When introduced to the soil, they improve the growth and development of plants, and by interacting with the climatic and soil conditions, they can improve the chemical composition of the vegetables. Research conducted in 2000–2001 aimed at the evaluation of the effect of different type sorbents introduced into the soil and the cultivation date on the concentration of some components in the Charlene lettuce cultivated in a film tunnel. Lettuce was grown in the presence of the following sorbents: potassium Ecosorb, sodium Acrygel, potassium Acrygel and sodium-potassium Acrygel during two terms: spring (April–May) and autumn (September–October). Based on the results of the two-year experiment, a significant effect of both experimental factors on the concentration of some components in the leaves of Charlene lettuce was observed. The concentration of L-ascorbic acid was determined by the type of sorbent used. In the first year of the experiment, the sodium-potassium Acrygel (14.2 mg%) was used to enhance the accumulation of vitamin C. In the second year, the sodium Acrygel (12.5 mg%) enhanced the accumulation of vitamin C. The spring plants accumulated higher levels of total sugars (in 2000 – 1.51% more, in 2001 0.68% more) in comparison to the autumn plants. The lettuce grown in the autumn had high concentrations of nitrates, averaging 2944.3 mg N-NO₃·kg fresh mass^-1.

59-68