Seed Biology and Principles of Seed Production
Seed Biology and Principles of Seed Production
This domain tests how seeds form, germinate and stay alive, and why a seed crop must be managed differently from a grain crop. Questions often target embryo structure, dormancy, viability and the biological principles behind genetic purity.
Core biology and principles
- A true seed is a fertilised ovule containing an embryo, stored food (endosperm or cotyledons) and a seed coat.
- Germination begins with imbibition, followed by enzyme activation, reserve mobilisation, radicle emergence and seedling establishment.
- Orthodox seeds survive drying to low moisture; recalcitrant seeds lose viability if dried.
- Dormancy can be imposed by a hard seed coat, an immature embryo or chemical inhibitors.
- Viability means living tissue; germination means producing a normal seedling under specified conditions.
Seed production principles: start from an approved seed class, maintain isolation, rogue off-types, prevent mechanical mixtures, harvest at physiological maturity and keep lot identity.
Worked example
A field has 12,000 plants and 36 off-types. Initial genetic purity = (12,000 − 36) ÷ 12,000 × 100 = 99.70%. After roguing 30 off-types, 6 remain: (12,000 − 6) ÷ 12,000 × 100 = 99.95%. If the certification standard is 99.5%, the field passes after roguing, but the inspection report must record both counts.
Traps that cost marks
Do not call a diseased plant an off-type unless the variant is heritable. Do not treat tetrazolium staining as proof of normal germination. Do not dry recalcitrant seed. Do not assume high germination means high genetic purity.