ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
Hylocereus undatus (Haworth) Britton and Rose growing in controlled environment chambers at 370 and 740 μmol CO2 mol−1 air showed a Crassulacean acid metabolism (CAM) pattern of CO2 uptake, with 34% more total daily CO2 uptake under the doubled CO2 concentration and most of the increase occurring in the late afternoon. For both CO2 concentrations, 90% of the maximal daily CO2 uptake occurred at a total daily photosynthetic photon flux density (PPFD) of only 10 mol m−2 day−1 and the best day/night air temperatures were 25/15°C. Enhancement of the daily net CO2 uptake by doubling the CO2 concentration was greater under the highest PPFD (30 mol m−2 day−1) and extreme day/night air temperatures (15/5 and 45/35°C). After 24 days of drought, daily CO2 uptake under 370 μmol CO2 mol−1 was 25% of that under 740 μmol CO2 mol−1. The ratio of variable to maximal chlorophyll fluorescence (Fy/Fm) decreased as the PPFD was raised above 5 mol m−2 day−1, at extreme day/night temperatures and during drought, suggesting that stress occurred under these conditions. Fv/Fm was higher under the doubled CO2 concentration, indicating that the current CO2 concentration was apparently limiting for photosynthesis. Thus net CO2 uptake by the shade-tolerant H. undatus, the photosynthetic efficiency of which was greatest at low PPFDs. showed a positive response to doubling the CO2 concentration, especially under stressful environmental conditions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.1995.tb06850.x
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