- The purity test is the first test to be made. Seed samples can contain impurities such as weed seeds, seeds of other crop species, detached seed structures, leaf particles and other material. The object of purity analysis is to determine the composition of the sample being tested by weight. To do this, a purity test is conducted, in which the working sample is separated into the following component parts:
- i) Pure seed refers to the species under consideration. In addition to mature, undamaged seed, it includes, undersized, shriveled, immature and germinated seeds, provided they can be definitely identified as the species under consideration, more over it includes pieces resulting from breakage that are more than one half their original size Pure seeds includes the following:
- A. Intact seeds
- B. Achenes and similar fruits like caryopsis, schizocarpand mericarp with or without pedicel, perianth and whether they contain true seed unless it is apparent and when difficult to identify.
- C. Pieces of seeds, achenes, mericarp and caryopsis resulting from breakage that is more than half the original size (Half seed rule). However, seeds of Leguminosae, Cruciferae and Coniferae are considered as inert matter if their seed coat is removed.
- D. Clusters of Beta or pieces of such clusters with or without seeds that are retained by 200 x 300 mm sieve.
- E. Florets and caryopsis of Grammae.
- * Florets and one flowered spikelet’s with an obvious caryopsis containing endosperm provided, also that, the caryopsis of particular genera and species have attained minimum sizes.
- * Free caryopsis
- * All florets and caryopsis (except broken florets and caryopsis half or less than half the original size and in the case of Dactylis glomerata excluding one-fifth of the weight of multiple floret in which the sterile floret extends to or beyond the tip of the fertile floret) remaining in heavy protein after blowing at an uniform blowing speed.
- With reference to specific species:
- Allium sp., Capsicum sp., Cucumis sp., and Lycopsersicon sp., seed with or without seed except pieces of seed more than 1/2 the original size with or without seed coat.
- ii) Other seeds shall include seeds and seed like structures of any plant species other than that of pure seed.
- iii) Inert matter includes seed units and all other matters and structures not defined as pure seed or other seed. It includes, seeds and seed like structures eg., achenes, caryopsis, mericarp and seeds of leguminaceae less than ½ the original size with no seed coat.
- To perform purity analysis, the working sample is kept over the purity work board at the base end. A small quantity of sample is brought to the middle of the board and split into two basic components as pure seed and inert matter. The inert matter is further divided as pieces of seeds less than 1/2 the original size, stones, pieces of leaves, weed seeds, other crop seed etc. The pure seed is further divided into pure seed and other distinct variety (ODV) etc. The pure seed and inert matter are weighed upto three decimals and percentage worked out. The weed seed, OCS, ODV are counted and reported as number per kg.
|
Participants