EFFECTS OF NITROGEN FORMS ON ENDOGENOUS PLANT HORMONES CONTENT IN DIFFERENT ORGANS OF WHEAT AFTER ANTHESIS

Abstract

Background and Aims Applying different forms of nitrogen is an important method to regulate nitrogen metabolism of wheat. Endogenous plant hormones play an important role in grain filling of wheat. The objectives of this study were to 1) elucidate the effects of nitrogen forms on endogenous hormones content in roots, flag leaves and grains of wheat after anthesis, and 2) find nitrogen application methods for the wheat cultivar `Yumai 49'. Methods Pot experiments utilizing a sandy loam soil and wheat cultivar 'Yumai 49' were completed during 2003-2005. Nitrogen forms were CONH_4_N (urea), NH_4_N(NH_4HCO_3) and NO_3_N(NaNO_3), and nitrification inhibitor dicyandiamide (DCD) was applied in CONH_4_N and NH_4_N treatments. Spikes of wheat which flowered on same day were marked and roots, flag leaves and grains were sampled at fixed dates. Each sample weighed 0.5 g FW and was stored at -40 ℃. The enzyme_linked immunosorbent assay (ELISA) method was used to determine the content of IAA, GA_3, ABA and ZR. Key Results Compared with NO_3_N treatment, GA_3 content in CONH_4_N treated flag leaves and IAA and ABA content in grains were higher 5-15 days after anthesis, and the grain_filling rate (GFR) was higher in this period. GA_3 content in CONH_4_N treated roots, IAA and GA_3 content in flag leaves, and ABA content in grains were higher, IAA content in grains was lower 15-25 days after anthesis, and the GFR was lower in this period. Compared with NO_3_N treatment, ZR content in grains was higher 5 days after anthesis in all NH_4_N treatments. IAA and ABA content in grains was lower about 15 days after anthesis, and the GFR was lower in this period. ZR and GA_3 content in roots, IAA and GA_3 content in flag leaves, and ABA and GA_3 content in grains were lower, ABA content in flag leaves and IAA content in grains were higher 15-25 days after anthesis and the GFR was higher in this period. Compared with NO_3_N treatment, the grain weight of wheat was significantly greater in NH_4_N treatment, and grain yield was increased significantly either in NH_4_N or CONH_4_N treatments. Conclusions This study showed that endogenous hormones in wheat responded differently to nitrogen forms after anthesis. The GFR of wheat regulated by nitrogen forms was realized through the balance of endogenous hormones in roots, flag leaves and grains. We recommend that CONH_4_N or NH_4_N mixed with DCD be applied to wheat cultivar `Yumai 49'.