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Abstract Detail


Physiological Section

Fondom, Nicolas Y [1], Castro-Nava, Sergio [2], Huerta, Alfredo J. [3].

Photosynthesis and diel carbon balance under natural conditions in two Peperomia species that differ with respect to leaf anatomy: Part 1- The rainy season.

Background and Aims The occurrence of crassulacean acid metabolism (CAM) and C3 photosynthetic activities in Peperomia species has been linked to the differential distribution of C3 and C4 photosynthetic enzymes within the distinct leaf tissue layers. We studied under field conditions, photosynthesis and water relations of Peperomia obtusifolia and P. macrostachya, species that differ in leaf anatomy.
Methods Gas exchange and diurnal acid fluctuations were measured over a complete 24 hour photoperiod. Water potential measurements were determined at dawn and dusk while chlorophyll a fluorescence data were collected during the day (11 hr) and again at night (23 hr). Thickness of the distinct leaf layers was determined with the aid of a calibrated light microscope.
Key Results Gas exchange and diurnal acid fluctuations showed that when well-hydrated, P. obtusifolia has typical C3 activity and P. macrostachya has typical CAM activity with spongy mesophyll layer thickness of 28% and 72% respectively. Peperomia macrostachya had a lower leaf osmotic potential at dawn, likely due to malic acid accumulation. The chlorophyll a fluorescence parameter Fo was higher at night for both species, with significant differences observed only in P. obtusifolia. Quantum yield of PSII (ΦPSII), was high during the day for P. obtusifolia and at night for P. macrostachya while NPQ and qP values were high during the day for P. macrostachya and at night P. obtusifolia. The value of Fv/Fm did not show any significant change between day and night for either species. Differences observed in ΦPSII, qP and NPQ could be attributed to the differential mode of photosynthesis since both species were fully hydrated.
Conclusions Under well-hydrated conditions under natural conditions, a thicker spongy mesophyll layer correlates with the presence of CAM in the two Peperomia species studied and probably also in other Peperomia species


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1 - Miami University, Botany Department., Pearson Hall Room 316, Oxford, Ohio, OH 45056, USA
2 - Universidad Autonoma de Tamaulipas- UAT, Unidad Academica Multidisciplinaria Agronomia y Ciencias., CU Victoria, Tamaulipas, CP 87149, Mexico
3 - Miami University, Department of Botany, Oxford, Ohio, 45056, USA

Keywords:
Crassulacean acid metabolism (CAM)
Photosynthesis
Peperomia obtusifolia
Peperomia macrostachya
spongy mesophyll
hydrenchyma
PSII quantum (ΦPSII)
Non-photochemical quenching (NPQ).

Presentation Type: Poster:Posters for Sections
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P56001
Abstract ID:919


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