Seed Preparation Tools for TZ Testing
Annette Miller USDA/ARS NCGRP
A sharp blade, needle and fine point tweezers are usually all that
is needed to prepare many kinds of seeds for TZ testing.
Occasionally we must prepare seeds with exceptionally hard
covering structures, spherical or glossy seeds that are difficult to
hold, or seeds with delicate embryos that must be extracted with
a minimum of artifact damage.
Artifacts are abnormal staining patterns or apparent defects
that are a consequence of preparation techniques. Artifacts
are not true defects in seeds.
Appropriate tools can help us limit artifact damage. This survey
of tools is intended to provide ideas to help analysts improve
their seed preparation techniques.
Tools covered here fall into two broad categories:
1. grasping tools
2. cutting and dissecting tools
Safety and ergonomics will also be covered.
Grasping Tools
The single most essential tool of the seed analyst is tweezers or
forceps. Suppliers use the terms tweezers and forceps
interchangeably. Analysts rely on fine tip straight edge
tweezers with flat inner edges and a delicate spring action. This
is easiest on the hand muscles and the straight edge allows one
to draw seeds easily across a purity board. This workhorse tool
is great for grasping and even some dissection. However, its
limitations are apparent when working with larger seeds or
spherical seeds. Tweezers with concave inner edges, pearl
tweezers, or blunt tip larger tweezers with scored inner edges
provide improved grasping for larger seeds.
Clockwise from top:
1. straight edge, fine point, flat inner edges,
2. blunt tip, scored inner edges,
3. concave inner edges
4. pearl tweezers
Sliding clasp locking mechanisms are also available on some
tweezers. The sliding clasp is moved forward towards the tip to
clamp the two parts of the tweezers together.
Other grasping tool options include right
angle tweezers, hemostats, surgeon’s
grasping tools, pliers, wrenches, “C” clamps
and jewelers’ vise. Hemostats and
surgeon’s grasping tools have scissor type handles that lock.
Pliers differ from tweezers in that they have heavier, blunt tips
with ridged inside edges. A myriad of shapes and sizes are
available: fine tipped with curved, straight or right angle tips
(electronic supply), needle-nosed, and standard pliers.
Hemostats, locking tweezers and vises work well when seed
covering structures are exceptionally hard and woody and need
to be sawn, chiseled or hammered open.
jeweler’s vise (ring clamp)
surgeon’s grasping tool
with rubber tips
(hemostat has metal tips - not
shown)
curved tip
pliers
wrench and pliers
the ultimate
grasping tool
Cutting Tools
Blades:
Single edge razor blades, scalpel blades, x-acto blades, and snapoff box cutters all offer suitable sharp edges for TZ seed
preparation. Scalpel blades and x-acto blades come in a variety
of shapes that provide improved cutting. (e.g. convex blade for
cereals)
Single edge razor blades with an “extra keen” narrow bevel are
economical and easy to use. Paint stores carry them in bulk.
Box cutter handles are available for such blades. Any straight
edge blade can be sharpened with a whetstone as needed.
Scalpel and X-acto handles are more ergonomic. Some come
with comfortable rubberized grips. Scalpel blade replacement
should be done carefully with pliers or in specialized blade
removal devices. Package used blades appropriately in sealed
boxes before disposal. Never throw used blades loosely into
general garbage pails or bags.
scalpel
razor
x-acto
box cutter
Finger protection:
A wide range of items can be used for finger protection with
single edge razor blades when the seed covering structures are
difficult to cut.
Tool handles: Some are available in soft-grip rubber
for improved comfort.
Saws, chisels, files, hammer
Some seeds have rigid and woody covering structures that will
ruin ordinary blades. Hobby suppliers offer serrated blades
available in a variety of tooth sizes. These can be used to saw
very thick, dense fruit or seed coats of large seeds. When a saw
cut is made in the desired place, transverse cutters or other tools
can be inserted to crack open the coat in a more precise way.
Sawblades, diamond files and mini-chisels work well for
chipping seed coats of large legumes and other hard seeded
species. A hammer is a satisfactory tool for Cornus embryo
extraction.
clockwise from top left:
1. fine saw blades
2. mini chisels
3. hammer (Cornus)
4. diamond files
Clippers
Clippers have two blades that cut from opposite sides. Fine and
medium clippers are available from manicure/pedicure suppliers.
Heavy duty clippers and “guillotine” type clippers are available
from pet supply stores. Electronic supply stores carry heavy
duty transverse blade clippers with wide and narrow tips.
Comfortable handles are important, since these take more effort
to use. Heavy duty clippers are especially useful for grasses
with woody glumes and rachis segments that enclose the
caryopsis (e.g. Tripsacum, Buchloe).
Clockwise from top left:
1. fine
2. medium
3. heavy duty
4. “guillotine” type
Transverse clippers come in different sizes and are a
comfortable way to clip hard seeds (especially the tip of
Ipomoea).
narrow tip
wide tip
Dissecting and piercing tools
The ordinary laboratory dissecting needle is a very important aid
during evaluation. Although it is helpful for probing and
discerning tissue texture, the dissecting needle is often too blunt
for piercing very tiny seeds. Extra fine hand-sewing needles or
acupuncture needles work better for preparations that require
piercing the seed. A micro pin vise or a piece of masking tape
on the eye end facilitates grasping the needle.
above: standard
laboratory
dissecting needle
right: fine sewing
needle
Embryo excision is prescribed for several cereals in the ISTA
Working Sheets on Tetrazolium Testing. A spear tipped
dissecting needle is recommended for this procedure. The spear
tip has gently convex faces and two sharpened edges that come
to a point. The point is inserted at either end of the embryo.
The edges cut through the tissue
from the side and the smooth convex
face of the spear gently lifts out the
embryo (scutellum side) with a
minimum of artifacts. An artist’s
knife might also be used the same
above: spear tip dissecting needle
way.
below: artist’s knife
Cutting surfaces:
• germination media:
o blotters
o towels
o filter paper
• linoleum
• rotary cutter mats
• hard rubber mats
• plastic culinary cutting boards
General tool sources:
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agricultural/seed testing supplies
pet care (clippers)
manicure/pedicure supplies (tweezers, clippers)
electronics supplies (grasping and cutting tools like
transverse end cutters with ergonomic grips)
hobby supplies (www.micromark.com)
jewelers’ supplies
sewing notions
scientific and medical supplies
paint stores (single edge razor blades in bulk)
office supply: finger protectors
Specific tool sources:
“pearl tweezers”
www.jbfc.com/jewelry.htm
www.kassoy.com/tweezers01.html
www.ehobbytools.com/en-us/dept_9 html
www.shorinternational.com/TweezersStreaming.htm
“Full Spear” or “Dissecting needle with spear shaped head”
Carolina Biological Supply: www.carolina.com
Electron Microscopy Sciences:
www.emsdiasum.com/microscopy/products/tweezers/forceps.as
px?mm=15
heavy duty clippers:
http://store.yahoo.com/corradocutlery/heavydutbarsp.html
Hoffman manufacturing: www.hoffmanmfg.com
surgeon’s graspers, ergonomic (rubberized) x-acto handles,
mini chisels, finely serrated xacto blades, micro pin vise:
www.micromark.com
transverse end cutters:
www.swanstromtools.com
www.contacteast.com
www.rselectronics.com
tweezers and pliers with rubberized handles:
www.swanstromtools.com
compiled 5/2007 by Annette Miller USDA/ARS NCGRP