Effects of nutrient conditions to stem photosynthesis and growth in Ephedra intermedia (Ephedraceae)

ABSTRACT

Ephedra intermedia Schrenk et C.A.Meyer (Ephedraceae, Gnetales, Gymnospermae) contains ephedrine and pseudoephedrine, and has been used as Ephedra herb, a traditional medicine. Instead of degenerated leaves, photosynthetic assimilation is performed in their stems. Recently domestic cultivation of this species has been required, but relevant nutrient conditions for cultivation remain uncertain. In this study, we examined stem photosynthetic parameters in E. intermedia plants grown under different nutrient conditions in order to clarify relationships between the photosynthetic parameters and growth in their stems. Also, we examined whether the regulation of two photosystems of the photosynthetic electron transport system in E. intermedia stems is similar to that of angiosperm leaves. We cultivated E. intermedia plants under various nutrient conditions with different levels of nitrogen (N), and regularly measured CO₂ assimilation rates, parameters of the photosynthetic electron transport system, and growth of E. intermedia stems. The stem growth was better under the condition with the additional ordinary chemical fertilizer compared to those with urea or magnesium lime. The seasonal changes were observed in the CO₂ assimilation rates, Y(II), the quantum yield of photosystem II (PSII), and Y(ND), the non-photochemical yield due to donor side limitations in photosystem I (PSI). However, these parameters differed between nutrient conditions to small extents, and were not related to stem growth. Therefore, the measured parameters of photosynthesis could not explain the difference in stem growth between nutrient conditions. Although the photosynthetic parameters seasonally changed, the tight relationships between Y(ND), the PSI parameter, and Y(II) or Y(NPQ), the PSII parameters, were found throughout the seasons. These relationships between two photosystems in stems of gymnosperm E. intermedia were as the same as those in angiosperm leaves, although a flavodiiron protein can function as the electron sink in the stems of E. intermedia. This balance between two photosystems may be regulated by the system dependent on the thylakoid lumen pH, which may lead to the protection of two photosystems throughout the seasons.

KEY WORDS:

• Ephedra intermedia Schrenk et C.A.Meyer
• growth
• nutrients
• photosynthetic electron transport system
• stem photosynthesis

Acknowledgments

The authors would like to thank members of laboratory and Greenheart.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00380768.2024.2347919

Additional information

Funding

This study was supported by the JSPS KAKENHI (JP17H05729 and JP19H04732 to K.N.), CREST, JST (JPMJCR15O3 to K.N.), and AMED (JP16ak0101045 and JP21ak0101159 to K.M.).