Effects Of Infestation Of Brown Planthopper, Nilaparvata Lugens (St(?)l) (Homoptera: Delphacidae) On Nutrient Uptake In Rice Roots And Leaf Water Potential

The Brown planthopper, Nilaparvata lugens St?l (Homoptera: Delphacidae), is an important pest that impacts rice development and grain quality. The present study compared the difference in response of uptake of nitrogen (N), phosphorus (P), and potassium (K) by rice roots to the infestation of N. lugens on two rice varieties, Zhendao 2 (japonics rice) and Xieyou 63 (hybrid indica rice), at two developmental stages, beginning heading and grain filling stages, respectively. The objective of this study was to provide scientific aspacts for the breeding of resistance variety and effective control in field population. Main findings are as follows:1. Effect of N. lugens infestation on N, P, and K uptake by rootsAt 3 days (3DAI) after N. lugens infestation, there were significant differences in N uptake by roots between two varieties and among infestation densities, but there was no significant difference between heading and grain-filling stages. The percent reduction of N uptake by roots following N. lugens infestations on Xieyou 63 at the heading stage was significantly greater than on Zhendao 2 at the same stage; on the contrary to the heading stage, the effect of the infestations on N uptake by roots on Zhendao 2 at the grain filling stage was greater than on Xieyou 63 at the same stage. There was a positive linear correlation between N concentration in hydroponics solution and infestation density for two developmental stages, namely, the higher infestation density was, the greater on the effect of N uptake by roots. There were significant differences in P uptake by roots under N. lugens infestations between two varieties, two developmental stages and interaction effect for variety, developmental stage and infestation density. For Xieyou 63, the infestation of 30, 60, and 120 nymphs at the grain filling stage reduced P uptake by roots significantly, but the infestation of all densities at the heading stage did not. On the contrary to Xieyou 63, the infestation of all densities at the heading stage on Zhendao 2 reduced P uptake by roots. There were significant differences in K uptake by roots under N. lugens infestations between two varieties, two developmental stages and, among N. lugens infestation densities. There was maximum reduction on K uptake at the heading stage for two varieties. Generally, effect of N. lugens infestation N, P and K uptake at the heading stage was greater than that at the grain filling stage. The relationship between N. lugens infestation density and N, P and K concentrations showed significant correlation. The results at 6 and 9 DAI were similar to those at 3 DAI. Recovery rates of N, P and K uptake after removal of N. lugens from rice plants were related to rice variety, developmental stage and infestation duration. It took 3 d to not restore nutrient uptake to a normal level after being fed by 60 and 120 nymphs for 3 d at both heading and grain filling stages; but did to normal level at 6 days after removal of N. lugens. The recovery rate of the root system function of rice plants after removal of N. lugens for 60 nymphs infestation was faster than that for 120 nymph infestations. Concentrations of nutrient elements in hydroponics culture after removal of N. lugens significantly reduced, indicating that uptake function of plant gradually restored.2. Effect of N. lugens infestation on leaf water potential (LWP).Dynamics changes of LWP after N. lugens infestation on two rice varieties TN1 and Xieyou 963 at the tillering, heading and grain filling dstages were investigated using soil culture in potted rice. Leaf water potential (LWP) is a physiological indicator of plant. Environmental stress results in response of LWP to plant. Changes of LWP of rice plant under N. lugens infestation at the three developmental stages in two rice varieties, TN1 (susceptible to N. lugens) and Xieyou 963 (tolerance to N. lugens), were measured. LWP values varied with rice variety, N. lugens infestation density and infestation durations (days). The higher N. lugens infestation density is, the lower LWP. The longer infestation duration is, the lower LWP. Percent reduction of LWP values become larger with increase of N. lugens infestation density and infestation duration, compared to control (non-infestation). Percent reduction of LWP values in TN1 was greater than in Xieyou 963. LWP values can be considered as an index of resistance or tolerance of rice plant to pest infestation. The present findings have obvious implication for understanding of resistant physiology of rice variety to N. lugens.