Review Article

Naturwissenschaften

, Volume 89, Issue 4, pp 147-162

Ecology and ecophysiology of tree stems: corticular and wood photosynthesis

  •  H. PfanzAffiliated withInstitut für Angewandte Botanik, Universität Essen, 45117 Essen, Germany
  • ,  G. AschanAffiliated withInstitut für Angewandte Botanik, Universität Essen, 45117 Essen, Germany
  • ,  R. Langenfeld-HeyserAffiliated withInstitut für Forstbotanik, Universität Göttingen, 37077 Göttingen, Germany
  • ,  C. WittmannAffiliated withInstitut für Angewandte Botanik, Universität Essen, 45117 Essen, Germany
  • ,  M. LooseAffiliated withManaaki, Whenua Landcare Research, Canterbury Agriculture and Science Centre, Lincoln, Christchurch, New Zealand

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Abstract.

Below the outer peridermal or rhytidomal layers, most stems of woody plants possess greenish tissues. These chlorophyll-containing tissues (the chlorenchymes) within the stems are able to use the stem internal CO2 and the light penetrating the rhytidome to photoassimilate and produce sugars and starch. Although net photosynthetic uptake of CO2 is rarely found, stem internal re-fixation of CO2 in young twigs and branches may compensate for 60–90% of the potential respiratory carbon loss. Isolated chlorenchymal tissues reveal rather high rates of net photosynthesis (being up to 75% of the respective rates for leaf photosynthesis). Corticular photosynthesis is thus thought to be an effective mechanism for recapturing respiratory carbon dioxide before it diffuses out of the stem. Furthermore, chloroplasts of the proper wood or pith fraction also take part in stem internal photosynthesis. Although there has been no strong experimental evidence until now, we suggest that the oxygen evolved during wood or pith photosynthesis may play a decisive role in avoiding/reducing stem internal anaerobiosis.