Photosynthetic efficiency and quantitative reaction of bread winter wheat to mild short-term drought conditions

The effect of water reduction stress on photosynthetic efficiency and the agronomic traits of 10 bread winter wheat cultivars were investigated, with an aim to develop breeding methods for improving wheat drought tolerance. In the 2008 and 2009 crop seasons, the trial was grown in vegetative pots according to the method of a 2-factorial experiment (cultivar and treatment) as a randomized complete block with 3 replications. The stressed version of the treatment was exposed to mild water reduction short-term stress 3 times (at the end of tillering stage, at the flag leaf to beginning of heading stage, and at the grain filling stage). Three photosynthetic efficiency parameters (F_v/F_m, ET_0/ABS, and PI_ABS) were investigated at the end of the tillering stage (water content of soil: 22.4%–28.8% volume for the stressed variant and 29.8%–37.9% volume for the control), and 6 agronomic traits were estimated before and after winter wheat harvest. Significant differences were detected among cultivars for all investigated traits. The investigation revealed that water reduction stress decreased all examined agronomic traits. However, photosynthetic parameters mostly had higher values during mild short-term drought stress conditions. In addition, a significant interaction between cultivars and treatments was detected for 1000-grain weight and grain number per spike, but there was not any significant interaction for harvest index, number of spikes per pot, grain yield, and biomass per pot, nor for photosynthetic efficiency parameters.