Subject: guard cell development
From: [email-masked]
Date: 16 Jul 1994 06:04:10 -0700
Newsgroups: bionet.plants

Dear Ellen,
the pictures of Hetherington's poster showed blue staining of guard cells and 
neighbouring cells, therefore I assume they used the usual X-Gluc for staining.
From our experience, leakage of the stain from gc's sometimes occur in 
particular if strong staining is observed after long incubation. However, this 
looks different from Hetherington's pictures, as far as I can tell from 
my memory of the poster.
As Fred did not yet answer to the net, let me try to comment on your question 
about guard cell development. From viewing mature leaves we got the impression 
that gc development in Arabidopsis follows the path described as the 
"cruciferous-type" already in 1889 by Vesque (Bull. Soc. bot. Fr. 36, 41-77) 
and in detail for a number of brassicaceae by Pant and Kidwai (Ann. Bot. 31, 
513-521, 1967). In summary, stomatal development starts by an unequal division 
of a protodermal cell of the leaf. The smaller of the two daughter cells 
undergoes two further divisions, the last will give rize to the guard mother 
cell that will divide once more into the two guard cells. The divisions that 
ultimately give rize to the gmc occur in a spiral fashion (a newly formed cell 
wall will intersect with the previuously formed by an angle of about 60o) so 
that the gmc will be encircled by three other cells which enlarge during 
growth of the leaf. These neighbouring cells again may start to divide 
unequally to produce secondary or higher order stomata. Hopefully we can 
identify some of the factors involved in the regulation of this complex 
process by the analysis of our mutants.
With best wishes,
Thomas Altmann