Photosynthetic Electron Transport in the Liverwort Conocephalum conicum (Marchantiales)

Raymond J. Ritchie — 2025-05-08

Photosynthetic Electron Transport Rate (ETR) of Conocephalum conicum (Snakeskin Liverwort) was measured using PAM technology modelled using the Waiting-in-Line model. Plants were grown in greenhouses which had irregular sunflecks of full sunlight and in a culture room under LED lights. Plants grown in the greenhouse had photosynthetic maxima about 1/3 to ½ of sunlight, but very low optimum light requirements when grown in a culture room under LED lights. Chl a content was ≈ 241 mg Chl a m^-2 (Chl b/a ≈ 0.216). Mid-morning (10:30 solar time): Y_max ≈ 0.629, irradiance ½ point for Yield ≈ 231 μmol photon m^-2 s^-1; E_opt ≈ 910 μmol photon m^-2 s^-1. ETR_max ≈ 266 μmol e^- g^-1 Chl a s^-1, photosynthetic efficiency (Alpha, α0) ≈ 0.794 e^-photon^-1 g^-1 Chl a. Photoinhibition was significant at high irradiances. Photosynthesis was markedly diurnal: E_optand ETR_max were substantially lower in the afternoon. Integrating Gross photosynthesis (Pg) over the course of the day Pg ≈ 39.6 gC g^-1 Chl a d^-1 under full sunlight and ≈ 29.6 gC g^-1 Chl a d^-1 in the shaded greenhouse. On a projected surface area basis daily Pg is ≈ 7.14 gC m^-2 d^-1. The respiration rate was relatively low (≈ 2.23 μmol O₂ g^-1 Chl a s^-1) so net photosynthesis is positive even at very low irradiances. Greenhouse gown plants had a conspicuous diurnal pattern of photosynthesis where optimum rates were found in midmorning and midday with a decrease in the afternoon. Plants grown under LED lights had a very low E_opt(≈90 μmol photon m^-2 s^-1) and ETR_max (≈ 40 μmol g^-1 Chl a s^-1). pH experiments indicate that it is capable of using HCO₃^- as a carbon source.

Journal of Botanical Research

Photosynthetic Electron Transport in the Liverwort Conocephalum conicum (Marchantiales)