Physiological and biochemical changes during drought and recovery periods at tillering and jointing stages in wheat (Triticum aestivum L.)

Abstract

Defining the metabolic strategies used by wheat to tolerate and recover from drought events will be important for ensuring yield stability in the future, but studies addressing this critical research topic are limited. To this end, the current study quantified the physiological, biochemical, and agronomic responses of a drought tolerant and drought sensitive cultivar to periods of water deficit and recovery. Drought stress caused a reversible decline in leaf water relations, membrane stability, and photosynthetic activity, leading to increased reactive oxygen species (ROS) generation, lipid peroxidation and membrane injury. Plants exhibited osmotic adjustment through the accumulation of soluble sugars, proline, and free amino acids and increased enzymatic and non-enzymatic antioxidant activities. After re-watering, leaf water potential, membrane stability, photosynthetic processes, ROS generation, anti-oxidative activities, lipid peroxidation, and osmotic potential completely recovered for moderately stressed plants and did not fully recover in severely stressed plants. Higher photosynthetic rates during drought and rapid recovery after re-watering produced less-pronounced yield declines in the tolerant cultivar than the sensitive cultivar. These results suggested that the plant's ability to maintain functions during drought and to rapidly recover after re-watering during vegetative periods are important for determining final productivity in wheat.

Figure 1

Experimental design of the study: drought stress treatments were applied during tillering and jointing stages by withholding irrigation till the soil field capacity (FC) reached 35–40% and 55–60% for severe stress (SS) and moderate stress (MS), respectively. The drought treatments were maintained for 10 days by weighing the pots and compensating the water lost to the desired FC and then followed by re-watering at 75–80% FC. Severe and moderate water deficit treatments during tillering and jointing were designated as SS and MS, respectively, while, well-watered (control) was designated as WW treatments.

Figure 2

Effect of drought stress (SS: severe stress, MS: moderate stress and WW: well watered) on net photosynthetic rate (Pn) (A,B) and stomatal conductance (gs) (C,D) in Luhan7 (LH-7) and Yangmai16 (YM-16) wheat cultivars. SS and MS treatments were applied at 35–40% and 55–60% soil field capacity (FC), respectively for ten days at tillering and jointing growth stages followed by re-watering, whereas WW was maintained at 75–80% FC. Time-course of the measurements was one day before stress (0DS), 5^th and 10^th day of stress (5DS, 10DS), 1 and 3 days after re-watering (1DRW, 3DRW). Shaded areas indicate the measurements taken following re-watering. Each vertical bar above the means indicates standard error of six replicates (n = 6) by using two-way ANOVA at P < 0.05.

Figure 3

Effect of drought stress (SS: severe stress, MS: moderate stress and WW: well watered) on membrane stability index (MSI) (A,B) and membrane injury (MI) (C,D) in Luhan7 (LH-7) and Yangmai16 (YM-16) wheat cultivars. SS and MS treatments were applied at tillering and jointing growth stage at 35–40% and 55–60% soil field capacity (FC), respectively for ten days followed by re-watering, whereas WW was maintained at 75–80% FC. Time-course of the measurements was one day before stress (0DS), 5^th and 10^th day of stress (5DS, 10DS), 1 and 3 days after re-watering (1DRW, 3DRW). Shaded areas indicate the measurements taken following re-watering. Each vertical bar above the means indicates standard error of six replicates (n = 6) by using two-way ANOVA at P < 0.05.

Figure 4

Effect of drought stress (SS: severe stress, MS: moderate stress and WW: well watered) on the production of superoxides (A,B), hydrogen peroxide (C,D) and MDA contents (E,F) in Luhan7 (LH-7) and Yangmai16 (YM-16) wheat cultivars. SS and MS treatments were applied at tillering and jointing growth stage at 35–40% and 55–60% soil field capacity (FC), respectively for ten days followed by re-watering, whereas WW was maintained at 75–80% FC. Time-course of the measurements was one day before stress (0DS), 5^th and 10^th day of stress (5DS, 10DS), 1 and 3 days after re-watering (1DRW, 3DRW). Shaded areas indicate the measurements taken following re-watering. Each vertical bar above the means indicates standard error of six replicates (n = 6) by using two-way ANOVA at P < 0.05.

Figure 5

Effect of drought stress (SS: severe stress, MS: moderate stress and WW: well watered) on CAT (catalyses) (A,B), SOD (superoxidase dismutase) (C,D), and APX (ascorbate peroxidases) (E,F) activities in Luhan7 (LH-7) and Yangmai16 (YM-16) wheat cultivars. SS and MS treatments were applied at 35–40% and 55–60% soil field capacity (FC), respectively for ten days at tillering and jointing growth stage followed by re-watering, whereas WW was maintained at 75–80% FC. Time-course of the measurements was one day before stress (0DS), 5^th and 10^th day of stress (5DS, 10DS), 1 and 3 days after re-watering (1DRW, 3DRW). Shaded areas indicate the measurements taken following re-watering. Each vertical bar above the means indicates standard error of six replicates (n = 6) by using two-way ANOVA at P < 0.05.

Figure 6

Effect of drought stress (SS: severe stress, MS: moderate stress and WW: well watered) on GSH (reduced glutathione) (A,B) and carotenoids (C,D) contents in Luhan7 (LH-7) and Yangmai16 (YM-16) wheat cultivars. SS and MS treatments were applied at 35–40% and 55–60% soil field capacity (FC), respectively for ten days at tillering and jointing growth stages followed by re-watering, whereas WW was maintained at 75–80% FC. Time-course of the measurements was one day before stress (0DS), 5^th and 10^th day of stress (5DS, 10DS), 1 and 3 days after re-watering (1DRW, 3DRW). Shaded areas indicate the measurements taken following re-watering. Each vertical bar above means indicates standard error for six replicates. Each vertical bar above the means indicates standard error of six replicates (n = 6) by using two-way ANOVA at P < 0.05.

Figure 7

Effect of drought stress (SS: severe stress, MS: moderate stress and WW: well watered) on soluble protein (A,B), amino acid (C,D) and proline (E,F) production in Luhan7 (LH-7) and Yangmai16 (YM-16) wheat cultivars. SS and MS treatments were applied at 35–40% and 55–60% soil field capacity (FC), respectively for ten days at tillering and jointing growth stages followed by re-watering, whereas WW was maintained at 75–80% FC. Time-course of the measurements was one day before stress (0DS), 5^th and 10^th day of stress (5DS, 10DS), 1 and 3 days after re-watering (1DRW, 3DRW). Shaded areas indicate the measurements taken following re-watering. Each vertical bar above the means indicates standard error of six replicates (n = 6) by using two-way ANOVA at P < 0.05.

Figure 8

Effect of drought stress (SS: severe stress, MS: moderate stress and WW: well watered) on total soluble sugars (A,B) and fructose (C,D) production in Luhan7 (LH-7) and Yangmai16 (YM-16) wheat cultivars. SS and MS treatments were applied at 35–40% and 55–60% soil field capacity (FC), respectively for ten days at tillering and jointing growth stages followed by re-watering, whereas WW was maintained at 75–80% FC. Time-course of the measurements was one day before stress (0DS), 5^th and 10^th day of stress (5DS, 10DS), 1 and 3 days after re-watering (1DRW, 3DRW). Shaded areas indicate the measurements taken following re-watering. Each vertical bar above the means indicates standard error of six replicates (n = 6) by using two-way ANOVA at P < 0.05.