Weed Anatomy

Weeds are plants interfering with the interests
of people. They are regarded as problems especially by farmers, by industrial vegetation managers,
in ornamental production, in forestry or on sites
where vegetation can cause safety risks, for example
on railway tracks or along motorways. Some weeds
impose a health risk for people by causing allergic
reactions, such as Ambrosia artemisiifolia L. Others
are toxic to animals, such as Senecio jacobaea L.
which kills horses from time to time when eaten.

Classical books on plant anatomy start with cells
and tissues. They continue with characteristic plant
tissues, for example parenchyma, collenchyma, sclerenchyma, epidermis, meristems, phloem, xylem and
secretory structures. Organs and plant parts are
described thereafter: stem, root, leaves and reproductive organs. We will try to follow this structure with
examples from weeds in the first part of this book.

 The most frequent weed species, however, are either
annuals, biennials or non-woody perennials. For this
reason, we will not refer to noxious trees nor bushes.
Only higher plants are considered, that is algae or
mosses are excluded. The second part of our book
consists of short monographs of weeds with particular
reference to anatomy