The transverse orientation of stomata
by Butterfass T. (1987)
Botanisches Institut der Johann Wolfgang Goethe-UniversitätFrankfurt a. M. 11Federal Republic of Germany
in Bot. Rev (1987) 53: 415-441 – https://doi.org/10.1007/BF02858323 –
The orientation of cell walls co-determines development. The orientation of the slits of the stomata can be used for analyzing the factors involved.
A comprehensive and annotated list is given of those plant species most of whose stomata are known to be oriented transversely to the long axis of an organ or a main rib. Included are also species showing only a trend toward transverse orientation.
Transverse orientation is known from a few mosses, from Bennettitatae, fromAzolla and some other ferns, and from species of about 45 families of spermatophytes. It could be confirmed that succulent species show the trait more often than do other plants.
Two thirds of the species listed belong to the Caryophyllales and Santalales, a few only to Asteraceae, but none to Rubiaceae, Cyperaceae, Poaceae, or Orchidaceae. Hence, the incidence of succulent species or of species with some succulent traits within the two orders and the lack of such species among other taxa may account in part for the distribution.
On the other hand, many succulent species do not show transverse orientation whereas in, e.g., Casuarina and Tamaricaceae transverse orientation goes together with non-succulent xeromorphy; Azolla shows no xeromorphy at all. Various factors, separately or together, may be involved. Proposed mechanisms determining the orientation of cell walls have been compiled from literature and are discussed.