Effect of foliar application of plant growth regulators on nitrous oxide (N2O) emission and grain yield in wheat.

Agricultural soils are the major source of global nitrous oxide (N2O) emission, and more than two thirds of N2O emission originate from soil. Recent studies have identified that green plants contribute to transport of N2O to the atmosphere. We investigated the effects of foliar application of plant growth regulators (PGRs) and growth stimulating chemicals on N2O emission and wheat grain yield for 2 years. The PGRs' abscisic acid (ABA) and cytozyme (20 mg L-1), kinetin (10 and 20 mg L-1) and wet tea extract (1:20 w/w) along with distilled water as control were sprayed on wheat canopy at the tillering and panicle initiation stages. Our results showed that cytozyme and tea extract enhanced the plant dry biomass over control. Kinetin (10 and 20 mg L-1) and cytozyme increased the plant photosynthetic rate and photosynthate partitioning towards the developing grain. ABA (20 mg L-1) and kinetin (10 and 20 mg L-1) reduced the N2O emission over control primarily through regulation of leaf growth, stomatal density and xylem vessel size. Leaf area, stomatal density and xylem vessel size were found to be associated with N2O transport and emission. We concluded that use of ABA and kinetin can reduce N2O emissions without any impact on wheat grain yield.