Photosynthetic acclimation in a terrestrial CAM bromeliad, Bromelia humilis Jacq

Authors

  • M. FETENE,

    1. Technische Hochschule Darmstadt, Institut für Botanik Schnittspahnstraße 3-5, D-6100 Darmstadt, FRG
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    • *

      Permanent address: Addis Ababa University, Department of Biology, P.O. Box 1176, Addis Ababa, Ethiopia.

  • H. S. J. LEE,

    1. Forestry Commission, Forest Research Station, Alice Holt Lodge, Wrecclesham, Farnham, Surrey GU10 4LH, UK
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  • U. LÜTTGE

    1. Technische Hochschule Darmstadt, Institut für Botanik Schnittspahnstraße 3-5, D-6100 Darmstadt, FRG
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SUMMARY

Photosynthetic acclimation of a terrestrial CAM bromeliad –Bromelia humilis Jacq. to irradiance and nitrogen supply during growth was investigated under controlled conditions. Considerable acclimation to shade was realized through an increase in total chlorophyll, accessory pigments, an increase in chloroplast size and appressed to non-appressed thylakoid membrane ratio, and a reduction in chlorophyll a/b ratio. A relatively high apparent photon yield in shade was associated with a low light-compensation point and low dark-respiration rate.

Light saturation of integrated dark CO2 uptake occurred at a relatively low total daily photosynthetic photon flux density (PPFD) and was not influenced by growth PPFD level. Maximum photosynthetic capacity expressed per unit chlorophyll and nitrogen use efficiency were significantly higher in high-PPFD-grown plants. In addition, apparent photon yield was only slightly reduced in high-PPFD-grown plants with nitrogen, while maximum photosynthetic rate remained the same indicating radiationless dissipation of excess light.

Very high levels of recycling of respiratory carbon were observed under nitrogen deficiency in plants grown in both high and low PPFD. The extensive photosynthetic acclimation of B. humilis is discussed in terms of contrasting exposure and limitations of its natural environment.

Abbreviations
CAM

crassulacean acid metabolism

PPFD

photosynthetic photon flux density

NUE

nitrogen use efficiency

Ancillary