The weight method was used to measure the transpirationrate of corn seedlings. At about 10 o’clock in the morning, the potmouths were completely sealed with plastic film. The connectionsof plastic films with plastic films, pot edges and corn stem baseswere sealed with plastic tape. Vaseline was also applied to theseconnections to ensure a firm seal. The bases of the plastic pots weresealed by the same method. The pots were weighed using an elec-tronic balance (with readability of 0.01 g and weighting capacity of6200 g). After weighing, the aboveground parts of seedlings wereimmediately placed in a sunny and well-ventilated area. After 5 h,the aboveground parts were weighed again. The decrease in weightwas divided by 1 g/cm3to obtain the volume of transpiration. Tran-spiration rate was expressed as the volume of transpiration perhour. The root-to-leaf delivery rates of NO3−by transpiration wereexpressed as the product of its NO3−concentrations and their tran-spiration rates.