Seed Preparation Tools for TZ Testing Annette Miller USDA/ARS NCGRP

Transcription

1 Seed Preparation Tools for TZ Testing Annette Miller USDA/ARS NCGRP

2 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.

3 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

4 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. surgeon s grasping tool with rubber tips (hemostat has metal tips - not shown) jeweler s vise (ring clamp) wrench and pliers curved tip pliers the ultimate grasping tool

5 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

6 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.

7 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

8 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

9 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

10 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 way. above: spear tip dissecting needle below: artist s knife

11 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: 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 ( jewelers supplies sewing notions scientific and medical supplies paint stores (single edge razor blades in bulk) office supply: finger protectors

12 Specific tool sources: pearl tweezers html Full Spear or Dissecting needle with spear shaped head Carolina Biological Supply: Electron Microscopy Sciences: px?mm=15 heavy duty clippers: Hoffman manufacturing: surgeon s graspers, ergonomic (rubberized) x-acto handles, mini chisels, finely serrated xacto blades, micro pin vise: transverse end cutters: tweezers and pliers with rubberized handles: compiled 5/2007 by Annette Miller USDA/ARS NCGRP