Photosynthesis and translocation of assimilates in rice plants following phloem feeding by the planthopper Nilaparvata lugens (Homoptera: Delphacidae)

Experiments were conducted to measure the effect of feeding by the planthopper Nilaparvata lugens (St?l) on photosynthesis and the translocation of assimilates in rice plants, Oryza sativa L. We used mature japonica rice plants and applied the 13CO2 feeding method to evaluate those physiological effects. The photosynthetic rate was suppressed by N. lugens infestation, especially at the lower leaf position, with rates 30% lower than that of control plants at the booting stage. Leaf nitrogen concentration in infested plants was also lower than that in control plants. After flowering, the chlorophyll content and total plant dry weight were reduced by N. lugens. Stem and sheath dry weights were significantly reduced by N. lugens infestation, whereas panicle dry weight was not affected. Little effect was found on disruption in translocation of assimilates, even when 13CO2 was supplied to the infested leaves. Results suggested that removal of assimilates and reduction in photosynthesis by N. lugens have the greatest effect on growth and yield of rice plants as compared with the disruption in the translocation of assimilates. Plant death can occur by N. lugens infestation if the amount of energy supplied is less than that required for tissue maintenance.