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Tolerance of Poplar (Populus sp.) to Environmental Stresses II. Photosynthetic Characteristics of Poplar Clones Grown at Low and High Light Intensities

par Havaux, Michel C. ;Ernez, Mohamed ;Lannoye, Robert
Référence Journal of plant physiology, 132, 6, page (664-670)
Publication Publié, 1988

Article révisé par les pairs

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Résumé :

Four poplar clones (Populus sp., Beaupré, Raspalje, Fritzi Pauley and Robusta) were grown at low and high photon flux densities (PFD) and the photosynthetic characteristics of the leaves were examined and compared using photoacoustic and fluorometric techniques. The growth of all the clones (shoot length and leaf area) was markedly reduced under low PFD conditions. Photoacoustic measurements indicated that growth at low PFD induced a substantial increase in the maximal quantum yield for oxygen evolution. This increased quantum yield was apparently due to an increase in the size of the photosynthetic unit (number of chlorophyll molecules associated with each reaction center) and in the quantum efficiency of photochemistry in PS II, as indicated by measurements of chlorophyll fluorescence induction in the presence of DCMU. The maximal oxygen evolution rate as well as the light saturation level (minimal PFD for quantum yield = 0) were reduced in low-light-grown poplar cuttings. The photochemical quenching of chlorophyll fluorescence (qQ) was also decreased in shade-adapted plants- an effect which was particularly pronounced at high PFD above 1000 µmol m-2s-1. On the other hand, energy-dependent fluorescence quenching qE was much less affected: a noticeable increase in qE was, however, observed at moderate PFD (400–1000 µmol m−2 s−1). The same trends were observed in all the clones, although the amplitude of the changes described above varied from one clone to the other, with the Beaupre clone being apparently the least responsive to changes in the light environment. In contrast to leaves of poplar cuttings grown at high PFD which were not able to perform significant state 1-state 2 transitions, state transitions were clearly seen by modulated chlorophyll fluorescence changes in low-light-grown plants, indicating a better regulation and optimalization of the light distribution between the two photosystems in these latter plants. © 1988, Gustav Fischer Verlag, Stuttgart. All rights reserved.