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External application of regulator can reduce the damage of plants under low temperature stress, and 2,4-epibrassinolide (EBR) is a regulator that can enhance the cold resistance of plants. The study was aimed to investigate the influences of exogenous 2,4-epibrassinolide on the physiological characteristics of Dendrobium hybrida seedlings under low-temperature stress. In this study, the seedlings of Dendrobium hybrida ‘Sweel Maple’ were treated with various concentrations of EBR solutions (0, 0.1, 0.5, 1.0, 1.5, 2.0 mg/L) through foliar spraying, and then treated under 5 ℃ low-temperature in artificial climate chamber. The yellowing leaf rate, defoliation rate and the malondialdehyde (MDA), soluble sugar, soluble protein, proline and chlorophyll content of treated samples were measured. The results indicated that EBR could significantly reduce the rates of yellow leaves and defoliation in D. hybrida seedlings under temperature stress, with the optimal treatment concentration being 2.0 mg/L. Compared with the control, the rate of 50% yellow leaves, 100% yellow leaves, and defoliation decreased by 27.41%, 16.55% and 20.64%, respectively. Additionally, 2.0 mg/L EBR effectively mitigated the decline in chlorophyll content in seedlings’ leaves under low-temperature stress and decreased the relative electrical conductivity and MDA content. Specifically, the relative electrical conductivity decreased by 14.33% and the MDA content by 29.03%, compared to the control. Furthermore, 2.0 mg/L EBR enhanced the content of osmotic adjustment substances in the seedlings’ leaves under low-temperature stress. On the eighth day of stress, the soluble protein and soluble sugar contents reached 1.68 mg/mL and 46.49 mg/mL, respectively, while proline content peaked at 142.28 μg/mL on the second day after returning to normal temperature, which was significantly higher than that in the control. In summary, EBR effectively alleviated the damage caused by low-temperature stress to D. hybrida seedlings. Various indicators demonstrated that 2.0 mg/L EBR exhibited the most prominent effect in enhancing the seedlings’ cold resistance, making it the optimal treatment concentration.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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