vickery at JOLT.MPX.COM.AU
Wed Apr 30 01:37:06 EST 1997
Rod Savidge wrote:
>I have to disagree with the recent suggestion that "sclerenchyma should be
>abolished". In wood anatomy, `sclerenchyma' conveys the concept of
>secondary-walled and lignified cells distinct from tracheary elements.
>That is, sclerenchyma lack bordered pits whereas tracheary elements (at
>least those of secondary xylem) exhibit bordered pits. The distinction is
>important, not only from the functional stand point of whether or not the
>mature element is capable of water conduction, but also from the
>developmental stand point of cellular differentiation and its regulation.
I agree strongly with Doug Jensen here. He wrote ( in 'Re:
sclerenchyma/prosenchyma' ) :
>The problem I have with parenchyma, sclerenchyma, etc. is that people use them
>to refer to tissue types as well as cell types. I try present plants as
>composed of 3 tissue types: ground, epidermis, and vascular. Then I can
>discuss the cells that make up each type of tissue. I think this method is a
>bit less confusing to the students.
I assumed that 'sclerenchyma' is the name of a tissue and Rod assumed that
it is the name of a cell type. We were arguing at cross purposes. If
botanists can't agree, what hope have the students got?
Doug's suggestion may be the way forward; recognise only a few types of
tissue defined in terms of their ontogeny. This would have the advantage
of being close to the zoological concept of tissue, which, though I am very
hazy on zoology, is a collection of cells with a common origin in
embryology. This leaves open the question of what we should call the
entities defined by function, such as xylem, phloem, meristem etc.
bob at acsusun.acsu.unsw.edu.au
vickery at mpx.com.au
More information about the Plant-ed