Nitrogen-potassium balance improves leaf photosynthetic capacity by regulating leaf nitrogen allocation in apple

Abstract

Nitrogen (N) and potassium (K) are two important mineral nutrients in regulating leaf photosynthesis. However, the influence of N and K interaction on photosynthesis is still not fully understood. Using a hydroponics approach, we studied the effects of different N and K conditions on the physiological characteristics, N allocation and photosynthetic capacity of apple rootstock M9T337. The results showed that high N and low K conditions significantly reduced K content in roots and leaves, resulting in N/K imbalance, and allocated more N in leaves to non-photosynthetic N. Low K conditions increased biochemical limitation (B_L), mesophyll limitation (M_CL), and stomatal limitation (S_L). By setting different N supplies, lowering N levels under low K conditions increased the proportion of water-soluble protein N (N_w) and sodium dodecyl sulfate-soluble proteins (N_s) by balancing N/K and increased the proportion of carboxylation N and electron transfer N. This increased the maximum carboxylation rate and mesophyll conductance, which reduced M_CL and B_L and alleviated the low K limitation of photosynthesis in apple rootstocks. In general, our results provide new insights into the regulation of photosynthetic capacity by N/K balance, which is conducive to the coordinated supply of N and K nutrients.

Acknowledgements

This work was supported bythe National Key R & D Program of China (2023YFD2301000), the Special Fund for the Natural Science Foundation of Shandong Province (ZR2021MC093), the earmarked fund for CARS (CARS-27), the Taishan Scholar Assistance Program from Shandong Provincial Government (TSPD20181206), and Xin-lianxin Innovation Center for Efficient Use of Nitrogen Fertilizer (2020-apple).

Author contributions

S.G., Y.J., and X.X. conceived and designed the experiments. X.X., W.N., Y.G., C.L., Y.X., X.Z., J.L., Z.F., and G.T. performed all experiments. X.X, X.Z., and S.G. analysed the data and wrote the manuscript.

Data availability

The authors confirm that all experimental data are available and accessible via the main text and/or the supplemental data.

Conflict of interest statement

The authors declare they do not have any conflict of interest.

Supplementary data

Supplementary data is available at Horticulture Research online.

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