Effects of exponential fertilization on seedling growth and photosynthesis of Aquilarias spp

Exponential nutrient delivery accelerating seedling growth could bring about a steady state of nutrition in the plant and improve nutrient uptake. An exponential fertilization trial was conducted with six nitrogen dose levels (applying a total of 0，1 000，2 000，3 000，4 000，5 000 mg/seedling in this experiment)of nitrogen to research the effects of different nitrogen levels on growth and photosynthetic physiology of Aquilaria malaccensis and Aquilaria sinensis seedlings. It was indicated that nitrogen fertilization could bring a significant impact on growth and photosynthetic physiology of seedlings. Ground diameter, height and biomass of seedlings increased with the increase of nitrogen supply up to 3 000 mg/seedling, after then growth performance and biomass were unchanged. The total leaf area of A. malaccensis(1 995.33 cm2)and A. sinensis(1 366.57 cm2)fertilized by 3 000 mg/seedling achieved maximum, and the lamina mass per unit area (LMA) of A. seedlings was high at midgrowth. The nitrogen exponential fertilizations played an important role in the adjustment of net photosynthetic rate, transpiration rate and light response curves of Aquilaria seedlings. Under the nitrogen fertilization level (3 000 mg/seedling), the photosynthetic physiology characters of Aquilarias seedlings reached the maximums.