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Journal of Botanical Research
2025-03-27T15:39:11+08:00
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https://journals.bilpubgroup.com/index.php/jbr/article/view/9222
Photosynthetic Electron Transport in the Liverwort Conocephalum conicum (Marchantiales)
2025-03-27T15:39:11+08:00
Raymond J. Ritchie
raymond.ritchie@alumni.sydney.edu.au
<p>Photosynthetic Electron Transport Rate (ETR) of <em>Conocephalum conicum </em>(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 <em>a </em>content was ≈ 241 mg Chl <em>a </em>m<sup>-2</sup> (Chl <em>b/a </em>≈ 0.216). Mid-morning (10:30 solar time): Y<sub>max</sub> ≈ 0.629, irradiance ½ point for Yield ≈ 231 μmol photon m<sup>-2</sup> s<sup>-1</sup>; E<sub>opt</sub> ≈ 910 μmol photon m<sup>-2</sup> s<sup>-1</sup>. ETR<sub>max</sub> ≈ 266 μmol e<sup>-</sup> g<sup>-1</sup> Chl <em>a </em>s<sup>-1</sup>, photosynthetic efficiency (Alpha, α0) ≈ 0.794 e<sup>- </sup>photon<sup>-1</sup> g<sup>-1</sup> Chl <em>a. </em>Photoinhibition was significant at high irradiances. Photosynthesis was markedly diurnal: E<sub>opt </sub>and ETR<sub>max</sub> were substantially lower in the afternoon. Integrating Gross photosynthesis (Pg) over the course of the day Pg ≈ 39.6 gC g<sup>-1</sup> Chl <em>a </em>d<sup>-1</sup> under full sunlight and ≈ 29.6 gC g<sup>-1</sup> Chl <em>a </em>d<sup>-1</sup> in the shaded greenhouse. On a projected surface area basis daily Pg is ≈ 7.14 gC m<sup>-2</sup> d<sup>-1</sup>. The respiration rate was relatively low (≈ 2.23 μmol O<sub>2</sub> g<sup>-1</sup> Chl <em>a </em>s<sup>-1</sup>) 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<sub>opt </sub>(≈90 μmol photon m<sup>-2</sup> s<sup>-1</sup>) and ETR<sub>max</sub> (≈ 40 μmol g<sup>-1</sup> Chl <em>a </em>s<sup>-1</sup>). pH experiments indicate that it is capable of using HCO<sub>3</sub><sup>-</sup> as a carbon source.</p>
2025-05-08T00:00:00+08:00
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