Figures (9)  Tables (2)

    • Figure 1. 

      Maximum quantum efficiency of photosystem II (Fv/Fm) of winter wheat during a recovery period at 22 °C following a winter period of 0, 4, 10, or 20 d with surface ice (black), or winter desiccation treatment (no ice, grey) in growth chambers at −1 °C. Letters indicate differences between treatment and duration under treatment using Fisher's least significant difference (LSD) at p ≤ 0.05.

    • Figure 2. 

      Quantum yield of photosystem II (ΦII) for winter wheat plants during a recovery period at 22 °C following a winter period in growth chambers at −1 °C. The winter period was for either (a) 4, (b) 10, or (c) 20 d under surface ice (ice treatment), or winter desiccation (no ice treatment) for (d) 4, (e) 10, or (f) 20 d. Dashed lines indicate the average control group values of day 0 plants i.e. those that were cold acclimated only. Vertical lines indicate Fisher's least significant difference (LSD) values between genotypes on respective hours and days (p ≤ 0.05).

    • Figure 3. 

      Non-photochemical quenching (NPQ(T)) of winter wheat plants for the first 12-h recovery period (22 °C) after (a) 4, (b) 10, or (c) 20 d of surface ice (ice treatment), or (d) 4, (e) 10, and (f) 20 d of winter desiccation (no ice treatment) in growth chambers at −1 °C. Dashed lines indicate the average control group values of day 0 plants (i.e. those that were cold acclimated only). Vertical lines indicate Fisher's least significant difference (LSD) among genotypes on a given hour during recovery of each respective duration under treatment (p ≤ 0.05).

    • Figure 4. 

      Recovery of ΦNPQ values at 22 °C of winter wheat plants following winter dormancy (−1 °C), and (a) surface ice, or (b) winter desiccation for 20 d of treatment in growth chambers. Dashed lines indicate the average control group values of day 0 plants i.e. those that were cold acclimated only. Vertical lines indicate Fisher's least significant difference (LSD) values between genotypes on respective hours (p ≤ 0.05).

    • Figure 5. 

      Energy-dependent quenching (qE) of winter wheat plants during a recovery period (22 °C) following winter dormancy (−1 °C), and (a) 4, (b) 10, or (c) 20 d of surface ice, or (d) 4, (e)10, and (f) 20 d of winter desiccation treatment in growth chambers. Dashed lines indicate the mean of the control group (i.e. those that were cold acclimated). Vertical lines indicate Fisher's least significant difference (LSD) values between genotypes on a given hour of recovery (p ≤ 0.05).

    • Figure 6. 

      Photoinhibition (qI) responses during a recovery period (22 °C) of winter wheat plants following a winter period (−1 °C) with a surface ice treatment for (a) 4, (b) 10, or (c) 20 d or winter desiccation for (d) 4, (e) 10, or (f) 20 d of treatment in growth chambers. Dashed lines indicate the mean of day 0 (i.e. those plants that were only cold acclimated). Vertical lines indicate Fisher's least significant difference (LSD) values between genotypes on a given hour of recovery (p ≤ 0.05).

    • Figure 7. 

      Malondialdehyde content in (a) leaves, and (b) crown tissues of winter wheat in growth chamber conditions. Letters indicate significant difference between duration of treatment (p ≤ 0.05).

    • Figure 8. 

      Ascorbate peroxidase activity (APX) in (a) leaves as influnced by duration, (b) crowns in response to genotype, and (c) crown tissues in response to duration. Peroxidase activity (POD) in (d) leaves in response to duration and (e) leaves and (f) crowns in response to stress treatment of winter wheat in growth chamber conditions. Letters indicate significant differences based on Fisher's protected least significant difference values (p ≤ 0.05).

    • Figure 9. 

      Principal component analysis (PCA) of winter wheat genotypes following growth chamber winter conditions and surface ice treatment for (a) 4 d, (b) 10 d, and (c) 20 d or winter desiccation treatment for (d) 4 d, (e) 10 d, or (f) 20 d. The highest contributors to the variation are shown in red, and the lowest shown in blue. These groupings are based on maximum efficiency of photosystem II (Fv/Fm), non-photochemical quenching (NPQ(T)), ΦNPQ, quantum yield of photosystem II (ΦII), and photoinhibition (qI).

    • Genotype Abbreviation Origin
      05222A1-1-2-7-1 PU Purdue University
      IL07-19334 UI University of Illinois
      MI16R0898 MSU Michigan State University
      OH15-131-31 OSU1 Ohio State University
      OH15-165-51 OSU2 Ohio State University
      OH15-89-68 OSU3 Ohio State University
      X11-0010-10-9-5 UK1 University of Kentucky
      X11-0081-8-10-3 UK2 University of Kentucky
      X11-0120-13-4-5 UK3 University of Kentucky
      X11-0249-17-17-3 UK4 University of Kentucky

      Table 1. 

      Soft red winter wheat genotypes, abbreviation, and university of origin.

    • Effect Fv/Fm ΦII ΦNPQ NPQ (T) qI qE APX POD MDA
      Leaf Crown Leaf Crown Leaf Crown
      Genotype (G) NS *** *** *** *** *** NS * NS * *** ***
      Duration of stress (D) *** *** *** *** *** *** *** *** *** NS *** ***
      Stress treatment (S) * *** NS NS *** *** *** NS *** * NS ***
      G × D NS *** *** *** *** *** NS NS NS NS NS **
      G × S NS ** *** *** *** *** NS NS NS NS NS NS
      D × S * *** *** ** *** *** *** NS NS NS NS **
      G × D × S NS *** *** *** *** *** NS NS NS NS NS NS
      Stress treatments included low temperature conditions combined with either surface ice or winter desiccation for a given duration. * p values ≤ 0.05, ** p value ≤ 0.01, *** p value ≤ 0.001, NS = not significant p > 0.05.

      Table 2. 

      Analysis of variance for main treatment factors and interactions of the maximum quantum efficiency of photosystem II in the dark-adapted state (Fv/Fm), quantum efficiency of PSII under steady-state actinic light (ΦII), nonphotochemical quenching (NPQ), photoinhibition (qI), photosynthetic efficiency energy quenching (qE), ascorbate peroxidase activity (APX), peroxidase activity (POD), and malondialdehyde content (MDA) of wheat plants exposed to simulated winter conditions in two experiments in growth chambers in 2021.