Correlation Between CAM-Cycling and Photosynthetic Gas Exchange in Five Species of Talinum (Portulacaceae)
Issue Date
1991Author
Harris, Fred S.
Martin, Craig E.
Publisher
American Society of Plant Biologists
Type
Article
Article Version
Scholarly/refereed, publisher version
Metadata
Show full item recordAbstract
Photosynthetic gat exchange and malic acid fluctuations were
monitored in 69 well-watered plants from five morphologically
similar species of Talinum in an investigation of the ecophysiological
significance of the Crassulacean acid metabolism (CAM)-
cycling mode of photosynthesis. Unlike CAM, atmospheric C03
uptake in CAM-cycling occurs exclusively during the day; at night,
the stomata are closed and respiratory C 0 2 is recaptured to form
malic add. All species showed similar patterns of day-night gas
exchange and overnight malic acid accumulation, confirming the
presence of CAM-cycling. Species averages for gas exchange
parameters and malic acid fluctuation were significantly different
such that the species with the highest daytime gas exchange had
the lowest malic acid accumulation and vice versa. Also, daytime
CO2 exchange and transpiration were negatively correlated with
overnight malic acid fluctuation for all individuals examined together,
as well as within one species. This suggests that malic
acid may effect reductions in both atmospheric CO: uptake and
transpiration during the day. No significant correlation between
malic acid fluctuation and water-use efficiency was found, although
a nonsignificant trend of increasing water-use efficiency
with increasing malic acid fluctuation was observed among species
averages. This study provides evidence that C 0 2 recycling
via malic acid is negatively correlated with daytime transpirational
water losses In well-watered plants. Thus, CAM-cycling could be
important for survival In the thin, frequently desiccated soils of
rock outcrops on which these plants occur.
Description
This is the publisher's official version, also available electronically from: http://dx.doi.org/10.1104/pp.96.4.1118
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Citation
Harris, F.S. and C.E. Martin. 1991. Correlation between CAM-cycling and photosynthetic gas exchange in five species of Talinum (Portulacaceae). Plant Physiol. 96: 1118-1124.
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