Transpiration and Carbon Acquisition in Root Hemiparasitic Angiosperms

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Abstract
Press, M. C. Graves, J. D. and Stewart, G. R. 1988. Transpiration and carbon acquistion in root hemiparastic angiosperms.—J. exp. Bot. 39: 1009–1014. Field measurements of carbon dioxide and water vapour exchange were made on eight species of root hemiparasite at sites in southern England, Scotland and northern Sweden. Rates of light-saturated photosynthesis and night-time respiration were of the same order of magnitude, ranging from 2.10 to 7.53 and − 2.76 to − 7.82 μmol m−2 s−1 respectively. We suggest that autotrophic carbon must be supplemented by a heterotrophic, host-derived supply. Day- and night-time transpiration rates were very high, ranging from 6.12 to 9.22 and 2.58 to 8.69 mmol m−25−1 respectively. High transpiration rates, day and night, will facilitate movement of water, inorganic and organic solutes from host to parasite. Whereas in autotrophic plants stomata function to minimize water loss and maximize carbon gain, in hemiparasites the reverse is the case, whereby water loss is maximized in order to maximize carbon gain.