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Studies in Stomatal Behaviour: VIII. STOMATAL RESPONSES TO TEMPERATURE AND CARBON DIOXIDE CONCENTRATION IN ALLIUM CEPA L., AND THEIR RELEVANCE TO MID-DAY CLOSURE

HANS MEIDNER and O. V. S. HEATH
Journal of Experimental Botany
Vol. 10, No. 29 (June 1959), pp. 206-219
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/23686551
Page Count: 14
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Studies in Stomatal Behaviour: VIII. STOMATAL RESPONSES TO TEMPERATURE AND CARBON DIOXIDE CONCENTRATION IN ALLIUM CEPA L., AND THEIR RELEVANCE TO MID-DAY CLOSURE
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Abstract

It has been reported in the literature that onion leaf stomata tend to close at noon (Loftfield, 1921) and that the minimum carbon dioxide concentration (Γ) in onion leaf tissue rises from 0.012 per cent. to 0.024 per cent. when the leaf temperature increases from 30° C. to 35° C. (light intensity 900 f.c.) (Heath and Orchard, 1957). Experiments were therefore carried out to test the hypothesis that raising the leaf temperature above about 30° C. causes stomatal closing movements in onion leaves (e.g. mid-day closure) by increasing the carbon dioxide concentration in the leaf tissue. This hypothesis has been supported by the results of these experiments. Another and diametrically opposed effect of temperature on stomatal movements in onion leaves has, however, been discovered, namely that, provided the carbon dioxide concentration in the leaf tissue is kept low, increases in temperature cause increases both in the rate of stomatal opening and in the final width of stomatal pores.

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