Effect of different soil water content effect on genotype expession in photosynthetic efficiency and leaf temperature in sunflower

Sunflower (Helianthus annuus L.) has high needs for water but can tolerate drought very well because, under stress conditions, its well developed root system can supply water and mineral nutrients from deeper soil layers. Reduced water content in soil affects plant growth and development, photosynthetic rate and causes rapid leaf senescence. In this study, we measured maximum quantum yield of photosystem II (Fv/Fm), photosynthetic performance index (PIABS) and leaf temperature (LT) on 13 sunflower genotypes at different soil water contents. By calculating stress tolerance indices (STI) of Fv/Fm and PIABS parameters we evaluated drought tolerance for every tested sunflower genotype at given soil water contents. The experiment was set up in vegetation pots in two treatments with different soil water contents (60% and 80% of field water capacity) in three replications. Based on the obtained results for Fv/Fm and PIABS and STI values of Fv/Fm and PIABS parameters, we concluded that genotypes 5 and 12 had higher tolerance at both treatments, as opposed to genotypes 2 and 13 which were less tolerant. These analyses will help breeders to select genotypes adapted to different farming areas which is, along with the use of recommended production practices, the background for profitable sunflower production