Carbon dioxide exchange in lichens: Estimation of internal thallus CO2 transport resistances [Sticta latifrons, Pseudocyphellaria amphisticta, cyphellae, pseudocyphellae, recycling, photorespiration, photosynthesis, water relations, hypae, alga]
1981
Snelgar, W.P. | Green, T.G.A. (Waikato Univ., Hamilton (New Zealand). Dept. of Biological Sciences) | Beltz, C.K.
The gaseous exchange pathways of Sticta latifrons Rich. and Pseudocyphellaria amphisticta Kremp. were examined using both light and scanning electron microscopes. The size and frequency of the pores in the gas exchange structures (cyphellae and pseudocyphellae) and in the medulla were measured and from these CO(,2) diffusion resistances were calculated. Pseudocyphellae were found to be smaller and more widely spaced than cyphellae, consequently the resistance of the pseudocyphellae, was much greater than that of the cyphellae. Medulla resistances were low in both lichens and are probably unimportant, even at high water contents. No evidence of hyphal swelling was found. Gas exchange structure resistances were more than fivefold greater than medulla resistances. It is suggested that this arrangement of resistances may simultaneously encourage refixation of respired CO(,2) and maintain a non desiccating environment for the lichen algae. The internal transport resistances calculated in this work approximate experimentally obtained values.
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