Photosynthetic product allocations of Pinus massoniana seedlings inoculated with ectomycorrhizal fungi along a nitrogen addition gradient

Sun Pengfei; Shen Yafei; Wang Lijun; Chen Tian; Zhang Meng; Xiao Wenfa; Cheng Ruimei

doi:10.3389/fpls.2022.948676

Photosynthetic product allocations of Pinus massoniana seedlings inoculated with ectomycorrhizal fungi along a nitrogen addition gradient

Front Plant Sci. 2022 Aug 12:13:948676. doi: 10.3389/fpls.2022.948676. eCollection 2022.

Authors

Sun Pengfei¹, Shen Yafei^{1

2}, Wang Lijun¹, Chen Tian¹, Zhang Meng¹, Xiao Wenfa^{1

2}, Cheng Ruimei^{1

2}

Affiliations

¹ Chinese Academy of Forestry, Key Laboratory of Forest Ecology and Environment of National Forestry and Grassland Administration, Ecology and Nature Conservation Institute, Beijing, China.
² Co-innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing, China.

Abstract

Quantifying the allocation of photosynthetic products among different carbon (C) pools is critical for understanding and predicting plant C turnover response to climate change. A field experiment with ectomycorrhizal fungi (EMF) and nitrogen (N) was established to investigate the effects on allocation of photosynthetic products in Pinus massoniana (Lamb.) seedlings given increased N deposition. Seedlings were subjected to N addition and symbiosis with EMF, and the short-term allocation of a ¹³C photosynthetic pulse into leaves, branches, stems, roots, and soil was traced. Photosynthetic rate and root respiration were measured. It was found that N addition changed the allocation pattern of photosynthetic products in various organs of P. massoniana. Furthermore, N addition, mycorrhizal symbiosis, and interaction of N and EMF, all increased the amount of C produced by photosynthesis. N application less than 60 kg N hm^-1 a^-1 could promote the transfer and allocation of photosynthetic products in P. massoniana organs, which peaks at 60 kg N hm^-1 a^-1, and the highest N treatment began to decrease at 90 kg N hm^-1 a^-1. EMF inoculation could expand the absorption area of plant roots to obtain more nutrients and synthesize more C and N compounds for promoting the growth of itself and the host plant, improving the net photosynthetic rate and the distribution of C produced by photosynthesis in various organs. This forms a benign C and N cycle, thereby reducing the effect of high N addition on plants. The optimal N addition concentration was 60 kg N hm^-1 a^-1, and the optimal EMF was Pt, which provides a theoretical basis for inoculating EMF during increasing N deposition in the future climate change scenario. This enables plants to distribute more photosynthetic products to their roots, thus affecting their own C distribution for promoting growth.

Keywords: 13C allocation; Pinus massoniana; ectomycorrhizal fungi; nitrogen addition; photosynthetic products.