Question

The steps of seed purity testing are listed below. Arrange the steps in chronological order i.e. from the first to the last.
(A). Critical examination of the sample and separating the pure seeds, weeds, etc., and weighing them individually
(B). Preliminary separation of the working sample
(C). Calculate the percentage by weight of each component to one decimal place and prepare the report
(D). Obtaining the working sample
Choose the correct answer from the options given below:

• A. (A), (B), (D), (C).
• B. (D), (B), (C), (A).
• C. (D), (B), (A), (C).
• D. (C), (B), (D), (A).

Hint:

Purity testing always begins with obtaining the representative working sample (D) and ends with calculating the weight percentages and compiling the official report (C).
This sequence logic helps identify the correct option.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Seed physical purity analysis determines the composition of a seed lot by weight.
It partitions a representative sample into four distinct components: pure seed, other crop seed, weed seed, and inert matter.
The analysis follows a precise sequence of steps prescribed by the International Seed Testing Association (ISTA).

Step 2: Detailed Explanation:
Let us trace the chronological steps of a standard seed purity test:
1.

Step 1: Obtaining the Working Sample (D): The testing process begins by reducing a large submitted sample down to a smaller, representative "working sample" using a mechanical seed divider (such as a Boerner divider).
The weight of this working sample is determined by the seed size, designed to contain approximately 2500 seed units.
2. Preliminary Separation (B): Once obtained, the working sample undergoes a preliminary separation.
Large inert matter, empty husks, or obvious contaminants are separated using sieves or blowing equipment to simplify the subsequent hand-sorting process.
3.

Step 2: Critical Examination and Separation (A): The working sample is then spread out on a purity work board.
The analyst conducts a detailed, seed-by-seed visual examination using magnifying lenses or microscopes.
The sample is physically separated into four components: pure seed of the crop under test, seeds of other crop species, weed seeds, and inert matter.
Each of these separated fractions is then weighed on a precision analytical balance.
4.

Step 3: Calculations and Reporting (C): Finally, the percentage by weight of each of the four components is calculated relative to the total starting weight of the working sample:
\[ \text{Component %} = \left( \frac{\text{Weight of Component}}{\text{Total Weight of Working Sample}} \right) \times 100 \] The values are rounded to one decimal place and recorded in the official seed analysis certificate.
Thus, the correct chronological sequence is (D) \( \rightarrow \) (B) \( \rightarrow \) (A) \( \rightarrow \) (C).

Step 3: Final Answer:
The correct chronological order of the steps is (D), (B), (A), (C), corresponding to option (C).