Effect of Short-Term Water Deficit on Some Physiological Properties of Wheat (Triticum aestivum L.) with Different Spike Morphotypes

Abstract

Water deficit is one of the most important stress factors affecting yield and production quality. Breeders are focusing on breeding wheat cultivars and crop lines that are more resistant to water deficit, so there is a possibility that plants with changes in their ear morphologies, such as long chaff and multi-rowed varieties, will be more resistant to water deficit. Therefore, our research focused on the study of changes in the physiological parameters of wheat cultivar ‘Bohemia’ (normal cob) with an altered morphotype (genotypes ‘284-17’ (long chaff) and genotype ‘29-17’ (multirow cob)), in relation to the duration of the water deficit. The experiment was set up as a container experiment under partially controlled greenhouse conditions. The experimental design included four treatments. The control (C) variant was irrigated regularly. The other treatments were stressed by water deficit, which was induced through the method of gradually drying the substrate: treatment D1 involved 10 days without irrigation, 4 days of watering, 10 days with a re-induced water deficit and 4 days of watering; treatment D2 involved 10 days of watering, and then stress was induced via water deficit until the end of the experiment; treatment D3 involved 10 days of stress and then irrigation until the end of the experiment. The pigment content, gas exchange rate, chlorophyll fluorescence and water potential were monitored in the juvenile wheat plants. The obtained results showed that the contents of photosynthetically active pigments (chlorophyll a and b and carotenoids) were influenced by the gene type. The chlorophyll and carotenoid content were higher in genotype ‘29-17’ (0.080 and 1.925 nM cm−2, respectively) and lowest in cultivar ‘Bohemia’ (0.080 and 0.080 nM cm−2, respectively). The chlorophyll content decreased due to water deficit most significantly in the D2 variant (0.071 nM cm−2), compared to the control (0.138 nM cm−2). The carotenoid content significantly decreased due to water deficiency in the cultivar ‘Bohemia’, D2 (0.061 nM cm−2) and the genotype ‘284-17’ (0.075 nM cm−2) and non-significantly decreased in ‘29-17’ (1.785 nM cm−2). In the control plants, the carotenoid content decreased in the following order: genotype ‘29-17’ (1.853 nM cm−2) > genotype ‘284-17’ (0.088 nM cm−2) > cv. ‘Bohemia’ (0.087 nM cm−2). Wheat plants had a decreased photosynthetic rate due to the closure of stomata and reduction in substomatal CO2 levels, which were caused by water deficit. The above effect was observed in genotype ‘29-17’ and cultivar ‘Bohemia’. The transpiration rate increased by 0.099 mM m−2 s−1 (5.69%) in the variety ‘Bohemia’, due to water deficit. On the other hand, the transpiration rate of genotype ‘29-17’ and genotype ‘284-17’ decreased by 0.261 mM m−2 s−1 (88.19%) and 0.325 mM m−2 s−1 (81.67%), respectively, compared to the control. Among the genotypes studied, genotype ‘29-17’ showed higher photosynthesis and transpiration rates, compared to genotype ‘284-17’ and the variety ‘Bohemia’. The effect of genotype and water deficit on chlorophyll fluorescence parameters was also shown. In all genotypes studied, there was a significant decrease in water potential due to water deficit, most significantly in the Bohemia variety, then in the genotype ‘284-17’, and the least significant decrease in water potential was seen in the genotype ‘29-17’. Genotype ‘29-17’ appears promising with respect to drought tolerance and photosynthetic rate, despite increased transpiration and reduced water potential; it also appears promising for better water management, with respect to reduced water potential in aboveground organs. On the other hand, the variety Bohemia appears to be less suitable for dry areas, since, despite its relative plasticity, it shows not only high water potential values in the water deficit region but also the most significant decrease in water potential.