Drought Tolerance in Cotton: Involvement of Non-enzymatic ROS-Scavenging Compounds

Compounds with reactive oxygen species (ROS)-scavenging ability were studied. High-performance liquid chromatography (HPLC) pattern of polyphenols, contents of proline and carotenoids, and antiradical (AR) capacity were determined. The malonyldialdehyde (MDA) level was also assessed. Tolerant and sensitive cotton genotypes were compared, grown in the Aegean region of Turkey at normal (field capacity) and limited (1/3 field capacity) water supply. Chlorogenic acid isomers and flavonoids were identified in HPLC pattern of polyphenols. At normal water supply, the tolerant genotype was distinguished by a higher content of all polyphenol types, higher proline, carotenoids and AR capacity and lower MDA level compared with the sensitive genotype. In plants subjected to water deficit, a decline of all polyphenol compounds, carotenoids and AR capacity was observed. However, this response was less pronounced in the tolerant than in the sensitive genotype, i.e. despite the stress conditions imposed, the tolerant plants maintained a more effective defence system. The data are corroborated by the weaker structural membrane damage in the drought-exposed tolerant vs. sensitive genotype, according to the MDA test. Hence, diverse chemical types are involved in the non-enzymatic ROS-scavenging system of cotton plants and can be related to the drought tolerance of this important crop.