Uv 8000

Seven days after germination, the whole plants of 5 hemp seedlings each from control, 20% PEG, and 20% PEG + GA₃ were taken to measure the physiological indexes, respectively.
The physiological and biochemical indices, including the activity of antioxidant enzymes (superoxide dismutase, SOD and peroxidase, POD), the content of osmotic regulation substances (soluble protein and soluble sugar) and lipid peroxidation (malondialdehyde, MDA), were determined using the methods described by Wang [18 ]. SOD activity in hemp seedling was measured by nitroblue tetrazolium (NBT) test. While POD activity was determined by monitoring the increase in absorbance at 470 nm as guaiacol was oxidised. Soluble protein content was measured by Bradford test. The lipid peroxidation level (measured as MDA content) in hemp seedlings was determined by thiobarbituric acid (TBA) test. Soluble sugar content was also determined by TBA test, but the increase in absorbance was measured at 450 nm. All absorbances were taken using a spectrophotometer (UV8000, METASH, Shanghai, China). Both SOD and POD activities were expressed as enzyme U/g (fresh weight, FW). The soluble protein, soluble sugar and MDA concentration (or content) were calculated as mg/g (FW), mmol/g (FW), and umol/g (FW), respectively.

The ninhydrin colorimetry was used to determine the proline content [23 ,24 (link)]. A 0.05 g fresh root sample was pooled in the centrifugal tube with 5 mL of 3% sulfosalicylic acid, extracted in the boiling water bath for 10 min, and shaken frequently. The extraction was filtered into a volumetric flask. Then, the volume was constant to 25 mL with distilled water. A total of 2 mL of extraction solution mixed with 2 mL of glacial acetic acid and 2 mL of acidic ninhydrin was added in a centrifuge tube. The mixture was treated with the boiling water bath for 30 min. After cooling down to room temperature, 4 mL of toluene was added to the mixture and shaken thoroughly. When they were stratified during standing, the absorbance of the upper solution was measured at 520 nm with an ultraviolet spectrophotometer (UV-8000, Metash, China).
The content of MDA and activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) were detected by assay kits (Suzhou Keming, China) [13 ]. A total of 0.1 g fresh samples and 1 mL solutions (1/10, v/v) were grounded in a water bath and centrifuged at 8,000 × g and 4℃ for 10 min. According to the manufacturer’s instructions, the supernatant absorbance was measured at 532 and 600 nm to assess MDA content, and at 470, 240, and 560 nm to evaluate the activities of POD, CAT, and SOD, respectively.

Fluorescence spectra of phenanthrene and its inclusion complex in aqueous solutions with different concentrations of rhamnolipid were recorded with a Hitachi F4600 fluorescence spectrophotometer; the fluorescence intensity was measured in a 1 cm quartz cell. Excitation wavelength used was set at 249 nm. The UV absorbance spectra of rhamnolipid solution, Cd (NO₃)₂ solution and rhamnolipid-cadmium solution were recorded with UV spectrophotometer (UV 8000, Shanghai Metash Instruments, China).