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Interactive effects of nitrogen and potassium on photosynthesis and photosynthetic nitrogen allocation of rice leaves

Hou, Wenfeng, Tränkner, Merle, Lu, Jianwei, Yan, Jinyao, Huang, Siyuan, Ren, Tao, Cong, Rihuan, Li, Xiaokun
BMC plant biology 2019 v.19 no.1 pp. 302
Oryza sativa, field experimentation, gas exchange, grain yield, leaves, nitrogen, nitrogen content, nutrient use efficiency, nutrients, photosynthesis, potassium, rice
BACKGROUND: Nitrogen (N) and potassium (K) are two important mineral nutrients in regulating leaf photosynthesis. Studying the interactive effects of N and K on regulating N allocation and photosynthesis (Pₙ) of rice leaves will be of great significance for further increasing leaf Pₙ, photosynthetic N use efficiency (PNUE) and grain yield. We measured the gas exchange of rice leaves in a field experiment and tested different kinds of leaf N based on N morphology and function, and calculated the interactive effects of N and K on N allocation and the PNUE. RESULTS: Compared with N0 (0 kg N ha⁻ ¹) and K0 (0 kg K₂O ha⁻ ¹) treatments, the Pₙ was increased by 17.1 and 12.2% with the supply of N and K. Compared with N0K0 (0 kg N and 0 kg K₂O ha⁻ ¹), N0K120 (0 kg N and 120 kg K₂O ha⁻ ¹) and N0K180 (0 kg N and 180 kg K₂O ha⁻ ¹), N supply increased the absolute content of photosynthetic N (Nₚₛₙ) by 15.1, 15.5 and 10.5% on average, and the storage N (Nₛₜₒᵣₑ) was increased by 32.7, 64.9 and 72.7% on average. The relative content of Nₚₛₙ was decreased by 5.6, 12.1 and 14.5%, while that of Nₛₜₒᵣₑ was increased by 8.7, 27.8 and 33.8%. Supply of K promoted the transformation of Nₛₜₒᵣₑ to Nₚₛₙ despite the leaf N content (Nₐ) was indeed decreased. Compared with N0K0, N180K0 (180 kg N and 0 kg K₂O ha⁻ ¹) and N270K0 (270 kg N and 0 kg K₂O ha⁻ ¹), K supply increased the relative content of Nₚₛₙ by 17.7, 8.8 and 7.3%, and decreased the relative content of Nₛₜₒᵣₑ by 24.2, 11.4 and 8.7% respectively. CONCLUSIONS: This study indicated the mechanism that K supply decreased the Nₐ but increased the Nₚₛₙ content and then increased leaf Pₙ and PNUE from a new viewpoint of leaf N allocation. The supply of K promoted the transformation of Nₛₜₒᵣₑ to Nₚₛₙ and increased the PNUE. The decreased Nₛₜₒᵣₑ mainly resulted from the decrease of non-protein N. Combined use of N and K could optimize leaf N allocation and maintain a high leaf Nₚₛₙ content and PNUE.