PSU 21

Floret with attached empty floret(s) not extending to the tip of the fertile floret (excluding the awn), or single floret, provided there is a caryopsis at least one-third the length of the palea measured from the base of the rachilla.

Special consideration:

• A fertile floret attached to another fertile floret shall be separated (see below for Festuca arundinacea exception).
• Attached glumes and empty florets extending to or beyond the tip of the fertile floret shall be removed and classified as inert matter (see below for Festuca arundinacea exception).
• For Bouteloua curtipendula, this PSU only applies if the submitted sample consists primarily of single florets and caryopses. When the submitted sample consists primarily of multiple florets and spikelets, refer to PSU 23.
• For Festuca arundinacea, a multiple seed unit consisting of one fertile floret with an attached glume or attached floret (empty or fertile) extending to or beyond the tip of the fertile floret shall be considered a pure seed unit, provided there is a caryopsis at least one-third the length of the palea measured from the base of the rachilla. A multiple seed unit consisting of three or more florets shall be broken apart and separated into pure seed (fertile florets) and inert matter (empty and sterile florets).

TWS Notes

PSD 33

Floret, with lemma and palea enclosing a caryopsis with or without awn.

Festuca, Lolium, ×Festulolium: size of caryopsis at least one-third the length of the palea, measured from the base of the rachilla. Caryopsis.

Piece of caryopsis larger than one-half the original size.

The floret may be with or without attached single fertile or sterile floret, provided that the attached floret does not extend to the tip of the fertile floret, excluding the awn (Fig. 3.1, 1–4).

Where a uniform blowing method is prescribed, see 3.5.2.5.

Multiple seed units

Seed units may consist of spikelets or parts of spikelets with more than one floret. Such structures with or without glumes are called multiple seed units (MSUs) when formed by the following structures:

• one fertile floret with one attached fertile or sterile floret that extends to or beyond the tip of the fertile floret, excluding the awns (Fig. 3.1, 8–12).
• one fertile floret with two or more attached fertile or sterile florets of any length (Fig. 3.1, 5–7).
• one fertile floret with basally attached sterile floret or glumes of any length (Fig. 3.1, 13–15).

MSUs are left intact and included in the pure seed fraction. However, the applicant may request that they be weighed and the percentage reported (see 3.5.2.6).

For Triticum turgidum L. subsp. dicoccon and Triticum aestivum L. subsp. spelta only: with or without rachis segment attached. In Triticum turgidum L. subsp. dicoccon and Triticum aestivum L. subsp. spelta, combinations of MSUs may be found. These are not to be separated in the purity analysis.

MSUs of Avena of the type of structure 13 (Fig. 3.1), where the lemma of the basal floret envelops the inner fertile floret, need not be reported as MSUs. All other structures (Fig. 3.1, 5–12, 14–15) are to be considered MSU.

Figure 3.1. Classification of single and multiple seed units. The stippled portion represents fertile florets and the clear portion sterile florets.

TWS Notes