Changes of the uptake function of rice roots to nitrogen (N), phosphorus (P), and potassium (K) in a hydroponics culture solution were studied in three experiments: a single factor experiment involving rice leaffolder, Cnaphalocrocis medinalis, larval infestations or simulated damages (cutting of leaves); paired combinations of two factors (leaf and root cuts); and combination of three factors (Nilaparvata lugens infestation and leaf and root removal). In the single-factor experiment, both C. medinalis feeding and leaf cutting significantly reduced the uptake of N by rice roots compared with the control. There were no significant differences in N concentration in hydroponics culture solution between treatments of one, two, and four larvae per hill, but there were significant differences between two rates of leaf cutting. Also, C. medinalis feeding and the cutting of leaves reduced the uptake of P by roots significantly but did not affect K uptake except when two-thirds of the leaf area was removed. In the two-factor experiment, root removal promoted the uptake of N by roots and there was a significant interaction between leaf and root cutting treatments. In contrast, leaf and root removal significantly decreased the P uptake but did not affect uptake of K. In the three-factor experiment, the effect by which cuts to the root system promoted the uptake of N by roots was counteracted by N. lugens infestation, and there were significant interactive effects on the uptake of N between the N. lugens infestation and the cuts in the leaf and root system. Also in the three-factor experiment, N. lugens infestation and leaf cutting reduced significantly the uptake of P and K by roots. The removal of rice roots had no significant impact on the uptake of P and K.