Tolerance of the photosynthetic apparatus in recombinant lines of wheat adapting to water stress of varying intensity

The stress tolerance index (STI) of leaf photosynthetic parameters was analysed in recombinant introgression lines of spring wheat (Triticum aestivum L.) grown under water stress of varying intensity in the simulated conditions of soil and soil-atmospheric drought. STI for the chlorophyll content was >1 regardless of experimental conditions. Carotenoids content increased only when soil drought occurred. Maximum quantum yield of PSII photochemistry was the most stable and stress-resistant parameter. Minimal fluorescence yield of the dark-adapted state was only sensitive to soil-atmospheric drought. Nonphotochemical quenching decreased under water stress, while parameters of the fast light curve based on chlorophyll fluorescence increased proportionally to the level of the stress load. We believe that these parameters are the most sensitive to the changes in the water supply of wheat plants, and are convenient for the rapid and noninvasive assessment of the wheat photosynthetic apparatus state under drought conditions.