Terminal heat stress causes a significant decline in yield of wheat by affecting its different reproductive phases. As an active biostimulant, fulvic acid can be used to ameliorate heat stress impacts in plants. To explore the effect of foliar applied fulvic acid a field experiment was carried out at Agronomic research area, University of Agriculture Faisalabad. Randomized complete block design with split plot arrangement having three replications was applied. In this experiment main plot treatments were comprised of heat stress (No heat, heat at booting stage and heat at grain initiation stage) and sub-plot treatments included foliar spray of fulvic acid at varying levels (0, 1.25, 2.50 and 3.75 mg L^-1). The data were recorded according to standard procedures regarding growth, yield, antioxidants and quality. These data were analyzed by using Fisher’s analysis of variance technique to determine its variability and difference in treatments’ means was compared by Tukey’s HSD test at 5 % probability level. Heat stress application at booting stage caused more decline in flag leaf fresh and dry weight, flag leaf area, spikelet per spike, spike length, number of grains per spike, fertile tillers, 1000-grain weight, grain yield, total soluble protein, chlorophyll a+b, leaf relative water contents and crude protein than heat stress at grain initiation stage. During no heat stress FA @ 1.25 mg L^-1 improved growth, antioxidants, chlorophyll and yield of wheat. During heat stress at booting stage FA @ 3.75 mg L^-1 performed well to increase crop performance, while during heat stress at grain initiation stage FA @ 2.50 mg L^-1 improved crop performance regarding growth, antioxidant activity, yield and quality. It is concluded that fulvic acid can be applied to improve crop growth and yield under normal and heat stress conditions.

Key words: Fulvic acid, Antioxidants, Heat stress, Growth, Quality, Wheat