The aim of this master's thesis was to investigate the effects of the prolonged presence of conventional polyethylene (PE) and biodegradable poly(butylene adipate-co-terephthalate) (PBAT) mulch films in soil on the growth, physiological status, and biochemical responses of sunflower (Helianthus annuus L.). The study included soil without added mulch film and soil in which PE or PBAT mulch films had been buried for 32 or 276 days. Sunflowers were grown in a growth chamber for eight weeks, after which growth parameters, water content, photosystem II efficiency, transpiration, and selected biochemical indicators of stress and antioxidant responses were determined. The results showed that the presence of mulch films in the soil did not reduce plant growth or cause persistent disturbances in the photosynthetic apparatus. Statistically significant differences were observed in several biomass parameters, root water content, hydrogen peroxide (H₂O₂) content in roots and shoots, and soluble sugar content in roots. The effects of the mulch films were most pronounced in the root system, where significant differences were found in water content, soluble sugar content, and H₂O₂ content. In contrast, no significant differences among treatments were detected for most photosynthetic parameters, antioxidant capacity, proline, or malondialdehyde (MDA) content. The results indicate that the prolonged presence of PE and PBAT mulch films in soil induces only mild, time-dependent changes in sunflower physiology and metabolism, with more pronounced effects in roots than in aboveground plant tissues.
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