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The effect of different growth conditions on dark and light carbon assimilation in Littorella uniflora
Author(s) -
Madsen Tom Vindbæk
Publication year - 1987
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1987.tb06129.x
Subject(s) - nutrient , photosynthesis , assimilation (phonology) , total inorganic carbon , botany , chemistry , carbon dioxide , biology , environmental chemistry , ecology , linguistics , philosophy
The effect of long‐term exposure to different inorganic carbon, nutrient and light regimes on CAM activity and photosynthetic performance in the submerged aquatic plant, Littorella uniflora (L.) Aschers was investigated. The potential CAM activity of Littorella was highly plastic and was reduced upon exposure to low light intensities (43 μmol m −2 s −1 ), high CO 2 concentrations (5.5 mM, pH 6.0) or low levels of inorganic nutrients, which caused a 25–80% decline in the potential maximum CAM activity relative to the activity in the control experiments (light: 450 μmol m −2 s −1 ; free CO 2 : 1.5 mM). The CAM activity was regulated more by light than by CO 2 , while nutrient levels only affected the activity to a minor extent. The minor effect of low nutrient regimes may be due to a general adaptation of isoetid species to low nutrient levels. The photosynthetic capacity and CO 2 affinity was unaffected or increased by exposure to low CO 2 , irrespective of nutrient levels. High CO 2 , low nutrient and low light, however, reduced the capacity by 22–40% and the CO 2 affinity by 35‐45%, relative to control. The parallel effect of growth conditions on CAM activity and photosynthetic performance of Littorella suggest that light and dark carbon assimilation are interrelated and constitute an integrated part of the carbon assimilation physiology of the plant. The results are consistent with the hypothesis that CAM is a carbon‐conserving mechanism in certain aquatic plants. The investment in the CAM enzyme system is beneficial to the plants during growth at high light and low CO 2 conditions.