PLANT PHYSIOLOGY , Vol 106, Issue 3 1065-1072, Copyright © 1994 by American Society of Plant Biologists
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ENVIRONMENTAL AND STRESS PHYSIOLOGY |
Aerenchyma Carbon Dioxide Can Be Assimilated in Typha Iatifolia L. Leaves
JVH. Constable and D. J. Longstreth
Department of Plant Biology, Louisiana State University, Baton Rouge, Louisiana 70803
Leaf structural characteristics and gas-exchange measurements were used to
determine whether photosynthetic tissue of Typha Iatifolia L. (cattail)
utilized CO2 from the aerenchyma gas spaces, part of an internal pathway
for gas transport in this wetland species. The partial pressure of CO2
(pCO2) in these aerenchyma gas spaces can be more than 10 times atmospheric
pCO2. The photosynthetic tissue occurred in structurally similar adaxial
and abaxial palisades, which were distinctly separated from each other by
the aerenchyma gas spaces. In each palisade there were three to four layers
of tightly packed, nonchlorophyllous cells separating the photosynthetic
tissue from the aerenchyma gas space. Different lines of evidence indicated
that CO2 conductance in the light was significantly greater across the
epidermal surface than across the internal surface of both palisades.
However, at an epidermal pCO2 of 350 [mu]bars and an internal pCO2 of 820
[mu]bars, the net rates of CO2 uptake (PN) across the epidermal and
internal surfaces were about equal. PN across the internal surface was
greater than across the epidermal surface at higher internal pCO2. Gas
space pCO2 can be greater than 820 [mu]bars in the field, and therefore, PN
across the internal surface could be a significant proportion of epidermal
surface PN.
