Photosynthesis in a Vanda sp orchid with Photosynthetic Roots
Copyright © 2020 Elsevier GmbH. All rights reserved.
| Veröffentlicht in: | Journal of plant physiology. - 1979. - 251(2020) vom: 30. Aug., Seite 153187 |
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| Format: | Online-Aufsatz |
| Sprache: | English |
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2020
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| Zugriff auf das übergeordnete Werk: | Journal of plant physiology |
| Schlagworte: | Journal Article CAM Homiochlorophylly in roots PAM Photosynthesis in roots and leaves Photosynthetic roots Vanda orchid |
| Zusammenfassung: | Copyright © 2020 Elsevier GmbH. All rights reserved. PAM fluorometry showed that the orchid Vanda sp (Gaud ex Pfitzers, Vandeae) had photosynthetic electron transport yields in leaves reaching ≈ 0.617 ± 0.262 at midday. Yield decayed exponentially as irradiance increased (Y½ = 128 ± 12.4 μmol photon m-2 s-1). Optimum irradiance (Eopt) for ETR (Photosynthetic Electron Transport Rate) was ≈ 369 ± 23.3 μmol photon m-2 s-1; the maximum photosynthetic ETR (ETRmax) (on a Chl a basis) ≈ 97.6 ± 3.76 μmol e-g-1 Chl a s-1. Rapid light curves exhibited classic photoinhibition at high irradiances: Vanda sp is a shade plant. Photosynthetic kinetics was strongly diurnal with minimal Eopt and ETRmax in the early morning, reaching a maximum at midday and decreasing in the afternoon. The aerial roots were normally photosynthetically dormant but rapidly activated when wet (homiochlorophyllous) then becoming dormant again after drying. Wet roots deliberately incubated under moist conditions had photosynthetic light curves comparable to leaves (Ymax ≈0.332, Y½ = ≈ 78.3 ± 27.8 μmol photons m-2 s-1, Eopt ≈ 278 μmol photons m-2 s-1 and ETRmax ≈ 317 ± 86.9 μmol e-g-1 Chl a s-1): wetting for only 15 min activated photosynthesis. Leaves showed a small degree of diurnal cycling of titratable acid but acid was accumulated in the early morning, not at night, this is a type of CAM-cycling. Titratable acid was low at sunrise (≈ 54.1 μmol H+g-1 FW), but increased until about 9 a.m. (≈ 137 μmol H+g-1 FW) and then gradually decreased over the course of the day |
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| Beschreibung: | Date Completed 08.12.2020 Date Revised 14.12.2020 published: Print-Electronic Citation Status MEDLINE |
| ISSN: | 1618-1328 |
| DOI: | 10.1016/j.jplph.2020.153187 |