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Optimal water‐use efficiency in a California shrub
Author(s) -
WILLIAMS WILLIAM E.
Publication year - 1983
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1983.tb01887.x
Subject(s) - conductance , assimilation (phonology) , shrub , stomatal conductance , chaparral , evaporation , environmental science , constant (computer programming) , atmospheric sciences , chemistry , mathematics , botany , photosynthesis , meteorology , physics , biology , computer science , biochemistry , programming language , philosophy , linguistics , combinatorics
. The stomatal behaviour of a California chaparral shrub was compared with that predicted by a model of optimal water‐use efficiency (Cowan & Farquhar, 1977). The daily courses of stomatal conductance, evaporation, and assimilation were calculated as was the derivative of evaporation with respect to assimilation (∂ E /∂ A ). The derivative ∂ E /∂ A was not constant, and the measured courses of conductance were not optimal, but daily courses of evaporation and assimilation were usually very close to what would have been predicted had ∂ E /∂ A been constant. This discrepancy arises because evaporation and assimilation are sometimes so severely constrained by the microenvironment that stomatal conductance has almost no effect on them.