Collection of Root Exudate from Duckweed

Materials and Reagents

1. Duckweed fronds, Spirodela polyrrhiza (collected from the paddy field drainage in the Tai Lake region of China)
   
2. Sterile deionized water
   
3. Methanol (HPLC grade) (Sigma-Aldrich, catalog number: 179337)
   
4. Hydrochloric acid (HCl) (Sigma-Aldrich, catalog number: 653799)
   
5. Formaldehyde solution (37 wt.% in H₂O) (Sigma-Aldrich, catalog number: 252549)
   
6. Sodium hypochlorite (NaClO) (available chlorine 4.00-4.99 %) (Sigma-Aldrich, catalog number: 239305)
   
7. 0.15% formaldehyde solution (see Recipes)
   
8. 0.5% v/v NaClO (see Recipes)
   
9. Modified Steinberg nutrient solution (see Recipes)
   

Equipment

1. Duckweed root exudate collection device (Figure 1)
   
   1. Plexiglass pot (D x H, 16 x 16 cm)
      
   2. Glass column (D x H, 23 x 170 mm)
      
   3. XAD-4 resin (20-60 mesh) (Sigma-Aldrich, catalog number: 37380-42-0)
      
   4. Hydrophobic fluoropore (PTFE) membrane (14 x 14 cm)
      
   5. Glass wool (Sigma-Aldrich, catalog number: 18421)
      
   6. Teflon stopper
      
   7. Aluminum foil
      
   8. Silicone tube
      
      
      Figure 1. Equipment used in root exudate collection
   
   
2. Clean bench
   
3. Peristaltic pump
   
4. Rotary evaporator (Tokyo Rikakikai, EYELA, model: N-1100D)
   
5. Freeze dryer (Freezone Plus 2.5) (Labconco)
   
6. Incubation chamber (23 ± 1 °C, under fluorescent lamps at 100 μmol/m/s, 16 h light/8 h dark)
   

Procedure