Effects Of BPH And Pesticide On Nutrient Uptaking Function Of Rice Root To Nitrogen, Phosphorus And Potassium

Studies of the effects of brown planthopper(BPH) infestations and of pesticides on physiology and biochemistry of rice plants have concentrated on the organs above ground and there is little understanding of the rice root. While the root of higher plants not only take up nutritional elements and water, but they also the place of synthesis of substance which effect physiological activity. This paper investigated the uptake of nutrients by rice root in relation to different BPH densities , duration of BPH infestation and pesticide applications. Three macronutrient including nitrogen (N),phosphorous(P) and potassium(K) were examined using the method of water culture solution. BPH infestation was shown to mainly affect the uptakes of P and K in the rice variety Zhengdao 2, hardly influencing the function of uptaking N in the subjected to five density of infestation (15, 30, 60, 90, 120). For Zhengdao 2, the relationship between BPH feeding duration and impact on the uptaking function of rice root for N appeared to be irregular, but the uptake of P and K by the roots declined significantly as BPH feeding duration prolonged. For Xiushui63, infestation for 2, 4, 6 and 8 days at a BPH density of 60 nymphs hardly influenced the uptake of N, but such an infestation level showed an significant effect on the uptake of P and K. After the removal of BPH, the function of rice root to uptake N recovered from infestation faster than to P and K in rice variety Zhengdao 2. While the recovery rate of uptaking function for K was faster than that for N and P in Xiushui 63. The recovery rate of nutrient uptaking function in rice roots was negatively correlated to the density and duration of BPH infestation. The experimental results demonstrated that BPH infestation at a density of 15 nymphs per hill over 7 days did not significantly influence the uptaking function of N, P and K. Infestation over 30 BPH did, however have a significant effect on the uptake function of the rice root. Linear regression equations between BPH density(X) and percentage of uptaking function reduction(Y) for P and K are as follow:Yp=319.10+3.096X r=0.8653 (Zhengdao 2)YK=0.8376+0.04356X r=0.9011 (Zhengdao 2)YK=2.7028+0.0481X r=0.9056 (xiushui 63)In two pesticides tested,high dose (225 and 300g.a.i/hm2)of jingganmycin treatment reduced uptake of P and K significantly, but little effect on uptake of N. Low dose(150g.a.i/hm2) of imidacloprid treatment promoted the uptake P and K significantly. There was also a significant interaction effect between BPH density and pesticide treatments. At a density of 30 BPH, 150g.a.i/hm2of jingganmycin treatment reduced uptake of N and P. At a density of 60 BPH, it reduced the uptake of K. At both 30 and 60 BPH densities, a high dose (450g.a.i/hm2) triazophos significantly reduced the uptake N and K by the root system.