Figure 1.
Overview of the control, heat acclimation and non-acclimation treatments used in this study.
Figure 2.
Morphology of strawberry plantlets 21 days after lethal temperature exposure. (A) T0 plantlet with healthy green leaves. (B) T3 plantlet with deterioration of original leaves and emergence of new leaves. (C) TN plantlet with deterioration of original leaves without new leaf growth. Bar = 1 cm.
Table 1.
Survival rates of heat-acclimated strawberry plantlets at different days after lethal heat stress.
| Treatment | 7 days | 14 days | 21 days | 28 days |
|---|---|---|---|---|
| T0 | 100 a | 100 a | 100 a | 100 a |
| T1 | 55 ± 0.31 b | 55 ± 0.10 b | 75 ± 0.36 b | 75 ± 0.36 b |
| T2 | 55 ± 0.10 b | 60 ± 0.00 b | 85 ± 0.36 b | 95 ± 0.32 ab |
| T3 | 70 ± 0.00 b | 85 ± 0.58 ab | 95 ± 0.14 ab | 100 a |
| T4 | 80 ± 0.26 b | 95 ± 0.32 a | 100 a | 100 a |
| TN | 0 c | 0 c | 0 c | 0 c |
Table 2.
Number of new leaves produced by heat-acclimated strawberry plantlets at different days after lethal heat stress.
| Treatment | 7 Days | 14 Days | 21 Days | 28 Days | 35 Days | 42 Days | 49 Days | 56 Days |
|---|---|---|---|---|---|---|---|---|
| T0 | 0.80 ± 0.13 a | 1.30 ± 0.21 ab | 2.20 ± 0.20 b | 3.10 ± 0.18 c | 4.20 ± 0.20 b | 5.10 ± 0.23 b | 5.70 ± 0.15 a | 6.00 ± 0.21 a |
| T1 | 0.10 ± 0.10 c | 1.00 ± 0.33 b | 2.10 ± 0.43 b | 3.50 ± 0.45 c | 4.40 ± 0.56 b | 5.00 ± 0.65 b | 5.80 ± 0.74 a | 6.30 ± 0.83 a |
| T2 | 0 | 1.30 ± 0.42 ab | 3.50 ± 0.43 a | 4.80 ± 0.42 a | 6.00 ± 0.54 a | 6.50 ± 0.45 a | 6.60 ± 0.43 a | 6.60 ± 0.43 a |
| T3 | 0.40 ± 0.16 b | 2.10 ± 0.31 a | 3.50 ± 0.40 a | 4.60 ± 0.54 ab | 5.20 ± 0.51 ab | 5.70 ± 0.45 ab | 6.50 ± 0.40 a | 7.40 ± 0.45 a |
| T4 | 0.40 ± 0.16 b | 1.50 ± 0.22 ab | 2.50 ± 0.22 b | 3.70 ± 0.30 bc | 4.60 ± 0.27 b | 5.40 ± 0.27 ab | 6.00 ± 0.26 a | 6.70 ± 0.33 a |
Table 3.
Number of new adventitious roots produced by heat-acclimated strawberry plantlets at different days after lethal heat stress.
| Treatment | 7 Days | 14 Days | 21 Days | 28 Days | 35 Days | 42 Days | 49 Days | 56 Days |
|---|---|---|---|---|---|---|---|---|
| T0 | 1.40 ± 0.40 a | 2.70 ± 0.56 a | 4.10 ± 0.72 a | 5.00 ± 0.98 a | 5.70 ± 1.09 a | 6.40 ± 1.28 a | 6.50 ± 1.32 a | 6.80 ± 1.31 a |
| T1 | 0 | 0 | 0.40 ± 0.31 bc | 1.10 ± 0.46 bc | 1.10 ± 0.46 cd | 1.80 ± 0.55 cd | 2.90 ± 0.80 b | 3.10 ± 0.77 b |
| T2 | 0 | 0.30 ± 0.21 bc | 0.60 ± 0.31 bc | 1.40 ± 0.69 bc | 1.50 ± 0.67 cd | 2.10 ± 0.64 c | 2.60 ± 0.82 b | 3.00 ± 0.84 b |
| T3 | 0.40 ± 0.27 b | 0.90 ± 0.28 b | 1.60 ± 0.37 b | 2.60 ± 0.50 b | 3.70 ± 0.50 b | 4.40 ± 0.50 b | 4.70 ± 0.50 ab | 4.80 ± 0.49 ab |
| T4 | 0 | 0.40 ± 0.22 bc | 1.30 ± 0.47 b | 1.80 ± 0.44 bc | 2.90 ± 0.43 bc | 3.20 ± 0.51 bc | 3.80 ± 0.61 b | 3.90 ± 0.60 b |
Table 4.
Number of new lateral roots produced by heat-acclimated strawberry plantlets at different days after lethal heat stress.
| Treatment | 7 Days | 14 Days | 21 Days | 28 Days | 35 Days | 42 Days | 49 Days | 56 Days |
|---|---|---|---|---|---|---|---|---|
| T0 | 0 | 0.80 ± 0.51bc | 1.20 ± 0.76 cd | 1.50 ± 0.82 c | 1.50 ± 0.82 c | 1.50 ± 0.82 cd | 1.50 ± 0.82 cd | 1.50 ± 0.82 c |
| Tl | 0 | 0.60 ± 0.50 bc | 1.80 ± 0.94 bcd | 2.40 ± 1.09 bc | 2.40 ± 1.09 bc | 2.90 ± 1.15 bc | 3.50 ± 1.22 bc | 4.60 ± 1.53 b |
| T2 | 0.50 ± 0.50 a | 1.60 ± 1.08 abc | 3.20 ± 1.44 abc | 4.50 ± 1.27 ab | 4.70 ± 1.21 ab | 5.10 ± 1.22 ab | 5.60 ± 1.14 ab | 6.10 ± 1.22 ab |
| T3 | 0 | 2.20 ± 0.66 ab | 4.80 ± 0.76 a | 5.60 ± 0.81 a | 5.70 ± 0.80 a | 6.30 ± 0.78 a | 7.00 ± 0.76 a | 7.20 ± 0.79 ab |
| T4 | 0.20 ± 0.20 a | 3.00 ± 0.67 a | 4.20 ± 0.79 ab | 4.50 ± 0.89 ab | 5.10 ± 0.81 a | 6.50 ± 0.64 a | 7.40 ± 0.52 a | 7.90 ± 0.38 a |
Table 5.
Chlorophylls, electrolyte leakage and free proline content of heat-acclimated strawberry plantlets after lethal heat stress.
| Treatment | Chlorophyll (mg · g-1 FW) | Electrolyte leakage (%) | Proline (mg · g-1 FW) | ||
|---|---|---|---|---|---|
| Total | Ch a | Ch b | |||
| T0 | 3.92 ± 0.02 a | 2.81 ± 0.02 a | 1.11 ± 0.04 a | 10.76 ± 0.04 c | 1.38 ± 0.41 b |
| T3 | 1.81 ± 0.04 b | 1.26 ± 0.02 b | 0.54 ± 0.03 b | 22.46 ± 0.70 b | 3.34 ± 0.13 a |
| TN | 1.11 ± 0.01 c | 0.75 ± 0.01 c | 0.36 ± 0.02 c | 38.26 ± 0.62 a | 1.69 ± 0.09 b |
Figure 3.
Activity of SOD (A), APX (B), GR (C), CAT (D) and POD (E) of strawberry plantlets following heat acclimation and lethal heat stress from 25°C to 48°C. Values are mean ± SE. Values followed by different letters are significantly different at p < 0.05, separated by Duncan’s multiple range test. APX, ascorbate peroxidase; CAT, catalase; GR, glutathione reductase; POD, peroxidase; SOD, superoxide dismutase.
Figure 4.
Antioxidant enzyme activities of the strawberry plantlets following the control (T0), heat-acclimation treatment (T3) and non-acclimation treatment (TN). (A) SOD, (B) APX, (C) GR, (D) CAT and (E) POD. Values are means ± SE. Values followed by different letters are significantly different at p < 0.05, separated by Duncan’s multiple range test. APX, ascorbate peroxidase; CAT, catalase; GR, glutathione reductase; POD, peroxidase; SOD, superoxide dismutase.