Nickel-enriched seed and externally supplied nickel improve growth and alleviate foliar urea damage in soybean

Official URL: http://dx.doi.org/10.1007/s11104-012-1284-6

The importance of seed Ni reserves for plant growth and N metabolism is poorly understood. This study investigated the effects of both seed Ni and externally supplied Ni on the impact of foliarly-applied urea and N-nutritional status of soybean. Soybean seeds were produced by growing plants in nutrient solutions containing different Ni levels, and their urease activities were measured. Plants were then grown from these seeds with or without external Ni. After treating half of the plants with foliar urea, the urea damage symptoms, elongation rates and chlorophyll concentrations were followed over one week. Biomass and mineral concentrations of different plant parts were determined. Nickel supply at increasing rates improved seed yield by up to 25 %. Seeds with Ni concentrations varying between 0.04-8.32 mg.kg(-1) were obtained. Depending on the Ni concentration, the seed urease activities differed up to 100-fold. Leaf damage due to foliar urea spray was significantly alleviated by higher seed Ni as well as external Ni supply. Higher Ni also promoted shoot elongation and improved chlorophyll concentrations. Nickel was 10-times more concentrated in the youngest part than in older leaves. In the absence of foliar urea, Ni enhanced the N concentration of the growing part of the shoot by up to 30 %. A better utilization of foliarly-applied urea-N is achieved in soybean when adequate Ni is supplied to plants by seed reserves and/or externally. High seed Ni levels are also required for preventing foliar urea damage and improving N remobilization.