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Figure 1. 

Effects of heat stress and exogenous chitosan on (a) turf quality and (b) shoot phenotype in creeping bentgrass exposed to non-stressed control and heat stress. Control + H₂O, foliar application with deionized water under non-stressed condition (25/20 °C, day/night); Control + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under non-stressed condition (25/20 °C, day/night); Heat + H₂O, foliar application with deionized water under heat stress (38/28 °C, day/night); Heat + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under heat stress (38/28 °C, day/night). Shoot phenotype was taken at 42 d of treatments. Different lowercase letters represent significant difference between different treatments during the experimental period (P ≤ 0.05). Error bars represent standard error (SE).

Figure 2. 

Effects of heat stress and exogenous chitosan on staining of (a) hydrogen peroxide and (b) superoxide in creeping bentgrass. Control + H₂O, foliar application with deionized water under non-stressed condition (25/20 °C, day/night); Control + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under non-stressed condition (25/20 °C, day/night); Heat + H₂O, foliar application with deionized water under heat stress (38/28 °C, day/night); Heat + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under heat stress (38/28 °C, day/night).

Figure 3. 

Effects of heat stress and exogenous chitosan on content of (a) ascorbic acid and (b) glutathione in creeping bentgrass. Control + H₂O, foliar application with deionized water under non-stressed condition (25/20 °C, day/night); Control + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under non-stressed condition (25/20 °C, day/night); Heat + H₂O, foliar application with deionized water under heat stress (38/28 °C, day/night); Heat + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under heat stress (38/28 °C, day/night). Different lowercase letters represent significant difference between different treatments during the experimental period (P ≤ 0.05). Error bars represent standard error (SE).

Figure 4. 

Effects of heat stress and exogenous chitosan on activities of (a) SOD, (b) CAT, and (c) POD in creeping bentgrass. Control + H₂O, foliar application with deionized water under non-stressed condition (25/20 °C, day/night); Control + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under non-stressed condition (25/20 °C, day/night); Heat + H₂O, foliar application with deionized water under heat stress (38/28 °C, day/night); Heat + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under heat stress (38/28 °C, day/night). Different lowercase letters represent significant difference between different treatments during the experimental period (P ≤ 0.05). Error bars represent standard error (SE).

Figure 5. 

Effects of heat stress and exogenous chitosan on activities of (a) APX, (b) GR, (c) DHAR, and (d) MDHAR in creeping bentgrass. Control + H₂O, foliar application with deionized water under non-stressed condition (25/2 °C, day/night); Control + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under non-stressed condition (25/20 °C, day/night); Heat + H₂O, foliar application with deionized water under heat stress (38/28 °C, day/night); Heat + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under heat stress (38/28 °C, day/night). Different lowercase letters represent significant difference between different treatments during the experimental period (P ≤ 0.05). Error bars represent standard error (SE).

Figure 6. 

Effects of heat stress and exogenous chitosan on expression levels of (a) AsFeSOD, (b) AsCu/ZnSOD, and (c) AsMnSOD in creeping bentgrass. Control + H₂O, foliar application with deionized water under non-stressed condition (25/20 °C, day/night); Control + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under non-stressed condition (25/20 °C, day/night); Heat + H₂O, foliar application with deionized water under heat stress (38/28 °C, day/night); Heat + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under heat stress (38/28 °C, day/night). Different lowercase letters represent significant difference between different treatments during the experimental period (P ≤ 0.05). Error bars represent standard error (SE).

Figure 7. 

Effects of heat stress and exogenous chitosan on expression levels of (a) AsCATA, (b) AsCATB, (c) AsCATC, and (d) AsPerox4 in creeping bentgrass. Control + H₂O, foliar application with deionized water under non-stressed condition (25/20 °C, day/night); Control + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under non-stressed condition (25/20 °C, day/night); Heat + H₂O, foliar application with deionized water under heat stress (38/28 °C, day/night); Heat + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under heat stress (38/28 °C, day/night). Different lowercase letters represent significant difference between different treatments during the experimental period (P ≤ 0.05). Error bars represent standard error (SE).

Figure 8. 

Effects of heat stress and exogenous chitosan on expression levels of (a) AsAPX1, (b) AsAPX2, (c) AsAPX3, (d) AsAPX4, (e) AsAPX5, (f) AsAPX6, and (g) AsAPX8 in creeping bentgrass. Control + H₂O, foliar application with deionized water under non-stressed condition (25/20 °C, day/night); Control + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under non-stressed condition (25/20 °C, day/night); Heat + H₂O, foliar application with deionized water under heat stress (38/28 °C, day/night); Heat + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under heat stress (38/28 °C, day/night). Different lowercase letters represent significant difference between different treatments during the experimental period (P ≤ 0.05). Error bars represent standard error (SE).

Figure 9. 

Effects of heat stress and exogenous chitosan on expression levels of (a) AsGR1, (b) AsGR2, (c) AsDHAR, and (d) AsMDHAR in creeping bentgrass. Control + H₂O, foliar application with deionized water under non-stressed condition (25/20 °C, day/night); Control + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under non-stressed condition (25/20 °C, day/night); Heat + H₂O, foliar application with deionized water under heat stress (38/28 °C, day/night); Heat + chitosan, foliar application with 100 mg∙L⁻¹ chitosan under heat stress (38/28 °C, day/night). Different lowercase letters represent significant difference between different treatments during the experimental period (P ≤ 0.05). Error bars represent standard error (SE).