Abstract
The relationship between nitrogen (N) sources and photosynthetic capacity of leaf differs between species. However, the leaf anatomical variabilities related to photosynthesis (A) of shrubs under different forms of N remain imperfectly known. Here, Lonicera Japonica (a shrub) was grown hydroponically in the presence of three forms of N (sole NH4+, 50%/50% NH4+/NO3− and sole NO3−). A and photosynthetic N use efficiency significantly decreased under sole NH4+ supply, in parallel with down-regulated stomatal conductance (gs), mesophyll conductance (gm), and electron transfer rate (J). Up to the total A decline of 41.28% in sole NH4+ supply (compare with sole NO3−), the gm attributed to 60.3% of the total limitations. Besides, the decreased internal air space explained the increase of gas-phase resistance, and the increased liquid-phase resistance in sole NH4+ supply was ascribed to the thicker cell wall thickness (Tcw) and decreased chloroplasts exposed surface area per unit leaf area (Sc/S). The discrepancy of Sc/S could be interpreted by the altered chloroplasts numbers and the distance between adjacent chloroplasts (Dchl-chl). These results indicate the alteration of Tcw and chloroplast numbers were the main causes of the difference in gm in coping with varied N sources.
Highlight Cell wall and chloroplast variability determining the mesophyll conductance under different nitrogen forms
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Yiwen Cao: 2020203071{at}stu.njau.edu.cn, Yonghui Pan: pyh2014{at}webmail.hzau.edu.cn, Tianheng Liu: 2020803194{at}stu.njau.edu.cn, Min Wang: minwang{at}njau.edu.cn, Shiwei Guo: sguo{at}njau.edu.cn