Improving Winter Wheat Performance by Foliar Spray of ABA and FA Under Water Deficit Conditions

Foliar spray of antitranspirants triggered plant adaptations to water stress and reduced the negative effects of drought on crop production. This study characterized the influence of exogenous abscisic acid (ABA) and fulvic acid (FA) application on winter wheat (Triticum aestivum L.) by pot experiment during 2012-2013 season and field experiment during 2012-2013 and 2013-2014 seasons in the North China Plain. In the pot experiment, plants were sprayed with FA or ABA under three irrigation levels (deficit, moderate deficit, and full irrigated). Field experiments involved three parts, including concentration and frequency of ABA application as well as the combined application of ABA and FA. Results showed that, compared with non-treated wheat grown under moderate deficit condition, both ABA and FA influenced the biomass allocation above and below ground, which caused the increase in crop harvest index as well as water use efficiency. By analyzing wheat performances in grain yield and transfer ratio of total assimilate (TRA) under different ABA concentrations (ranged from 30 to 60 mg/L) as well as ABA application frequencies (two, three, and four applications), results indicated that ABA worked well with lower concentration and less application frequency. At the heading stage of wheat, spraying FA improved the non-structural carbohydrate content (NCS) in plants. ABA application at the early grain-fill stage decreased residual NCS. In water deficit conditions, combined application of FA (at the heading stage) and ABA (at the early grain-fill stage) significantly improved the TRA and yield performance, and worked better than using separately.