Ideas for new Asteraceae PSU
Since 2003, analysts and other people familiar with
Artemisia tridentata have continued to work
on the testing problems of this species. In 2003,
Annette Miller of the Colorado State University’s
National Seed Storage Laboratory proposed the
following idea for a new pure seed unit definition
specifically for Artemisia tridentata: “PSU #49”:
“Intact achene unless, with
the use of transmitted light, it is obvious that
no seed is present. Achene with or without
attached floral remnants. Piece of broken
achene larger than one-half of the original
size, unless no seed is present. Seed, with or
without pericarp/seed coat. Piece of broken
seed, with or without pericarp/seed coat, larger
than one-half the original size.”
As
a participant in the 2004 Artemisia referee, as well
as a Registered Seed Technologist familiar with the
testing of many native Asteraceae species, the
author of this paper recognizes the need for
developing new PSU definitions for some of these
species.
It
may be helpful to use the current PSU definitions
for Poaceae (grass family) species listed in the
current (2004) AOSA Rules as a model. These
include PSU# 12, 13, 14, 15, 16, 17, 18, and 22.
All of these PSU definitions include the following
wording:
“… provided a caryopsis with some
degree of endosperm development can be detected
(either by slight pressure or by examination
over light).”
It
is important to note that in the AOSA Rules,
only members of the Poaceae family can be examined
in this manner when determining the pure seed.
However, it may be helpful to use a similar method
for examining members of the Asteraceae family.
The following are suggestions for two new PSU
definitions for Asteraceae, patterned after the
existing PSU definitions for the Poaceae and
Asteraceae in the AOSA Rules:
1. Intact
achene, provided a true seed with some degree of
embryo development can be detected (either by slight
pressure or by examination over light). Piece
of broken achene larger than one-half of the
original size, unless no seed is present. Seed,
with or without pericarp/seed coat. Piece of broken
seed, with or without pericarp/seed coat, larger
than one-half the original size.
2. Intact
achene, with or without one or more of the
following structures: beak, bristle, hairs, pappus,
wing or attached floral remnants, provided a true
seed with some degree of embryo development can be
detected (either by slight pressure or by
examination over light).
Piece of broken achene larger than one-half of
the original size, unless no seed is present. Seed,
with or without pericarp/seed coat. Piece of broken
seed, with or without pericarp/seed coat, larger
than one-half the original size.
