Effect of foliar application of ZnO nanoparticles on yield components, yield and Zn efficiency indices in rice under water stress

Zinc (Zn) plays an important role in reducing the negative effects of drought stress by regulating stomata and ionic balance in crops. On the other hand, application of Zn to nanoparticles form due to better uptake and transfer than conventional form can have better impacts on growth and yield in drought stress conditions. For this purpose, a field experiment was conducted to investigate the effect of foliar application of ZnO nanoparticles on yield components, yield and Zn efficiency indices in rice (cv. Tarom Hashemi) under deficit irrigation conditions as split plot in a randomized complete block design with three replications in Amol in 2016. Irrigation in four levels (I1: control or flood irrigation, I2: water stress at tillering stage for 15 days, I3: water stress at flowering stage for 15 days, and I4: water stress at grain filling stage for 15 days) were considered as main plots and foliar application of ZnO nanoparticles in four levels (Zn1: 0, Zn2: 25, Zn3: 50 and Zn4: 75 mg ZnO l-1) as sub-plots. The results showed that yield, yield components, as well as Zn concentration and uptake in grain and straw of rice were significantly decreased under water stress, especially at flowering stage. The use of 50 and 75 mg.l-1 ZnO nanoparticles resulted in improved the panicle length (2.7 and 3.6%, respectively), number of fertile tillers per hill (10.4 and 12.9%, respectively), number of filled grains per panicle (11.6 and 13.7%, respectively), Zn concentration (44.2 and 51.8%, respectively) and uptake (51.6 and 59.6%, respectively) in grain, and finally the grain yield (13 and 16.3%, respectively) compared with control. Therefore, the flood irrigation with application of 50 mg.l-1 ZnO nanoparticles is appropriate for improving the yield and Zn uptake in rice grains.