Biochemical responses of some (Helianthus annuus L.) cultivars to the interaction effects of biodegradable polymer and salt stress

Salt stress is one of the most important environmental factor limiting plant growth and causing serious agricultural problems in the world. Biodegradable poly(ethylene oxide)-co-(ε-caprolactone) poly(EO-co-ε-CL) copolymer synthesized by ring-opening polymerization (ROP) have been used to reduce this negative effect. For the characterization of this copolymer, the Fourier Transform Infrared (FT-IR), Proton Nuclear Magnetic Resonance (1H-NMR), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) techniques were used. To investigate the impact of copolymer and salt (200 mM NaCl) singly and in combination, on two different sunflowers (Helianthus annuus L. cv. 'Düet' and Helianthus annuus L. cv. 'Meteor') a series of experiments were established. In the seedlings grown for 21 days, differences in some metabolic parameters such as chlorophyll-a (Chl-a), chlorophyll-b (Chl-b), carotenoids (Car), total chlorophyll (Chl), total carbohydrate content, and malondialdehyde (MDA) content were examined. According to the result of our study, after the application of NaCl and poly(EO-co-ε-CL), significant changes were observed in the studied biochemical parameters. It was observed that the copolymer in both species had a healing effect against salt stress. Application of 200 mM NaCl caused an increase in MDA of both genotype, particularly in 'Meteor'. Higher Chl-a, Chl-b, total Chl, and Car contents were observed in 'Meteor' as compared to that in 'Düet' under saline conditions. Total carbohydrate content decreased with increasing salt stress in both cultivars.