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DIFFUSION THROUGH STOMATES
Author(s) -
Ting Irwin P.,
Loomis Walter E.
Publication year - 1963
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1963.tb06565.x
Subject(s) - diffusion , membrane , materials science , molecular diffusion , thermodynamics , chemistry , physics , metric (unit) , biochemistry , operations management , economics
Ting, Irwin P., and Walter E. Loomis. (Iowa State U., Ames.) Diffusion through stomates. Amer. Jour. Bot. 50(9): 866–872. Illus. 1963.—It is shown that the rule that diffusion through isolated, small pores is proportional to the diameter rather than the area of the pores is valid for pores of diameters as small as 20 μ, and that the curve extends to the origin at zero diameters, indicating that the law is effective throughout the range of stomatal sizes. Suggestions that an elliptical pore will be relatively more effective in diffusion than a circular one and that diffusion is concentrated at the periphery of the pore are not supported by experimental evidence and are physically improbable. Brown and Escombe's conclusion that there is no interference in the diffusion through the individual pores of a multiperforate membrane if the pores are spaced 10 diameters apart is not valid for diffusion through the stomates of a leaf. With pores of 200 μ and less spaced 10 diameters apart, interference increases rapidly with a smaller size and larger number of pores. As a result, the diffusion through a membrane with pores 19 μ in diameter and 190 μ apart was the same as that through a membrane with pores 132 μ in diameter and 1.32 mm apart, although the calculated capacity of the first membrane was 7 times that of the second. The diffusion of water vapor through multiperforate membranes with pores spaced 10 diameters apart has an apparent maximum of 65–70% of the diffusion through an open tube. Calculations of the effect of partial closing of stomates, using Verduin's equation for interference between pores, indicate that the theoretical diffusion capacity of 10 μ stomates spaced at 10 diameters would be increased several times by closing to an average diameter of 5 μ. This increase illustrates the dominant effect of interference in diffusion through small, closely spaced pores. Calculated diffusion through these stomates would not be decreased until they were more than 95% closed. It is concluded that stomatal opening will have no important effect on diffusion from or into a leaf until the stomates are essentially closed.