Legume Seed Anatomy

Cotyledon

Each "half" of a legume seed is a cotyledon. Therefore, legumes are known as dicotyledonous plants. Cotyledons are seed leaves and serve as a food supply for the seedling during germination and emergence. Legume seeds, like soybean or peanuts, contain considerably more oil and protein and less starch than cereal grains. (For example, soybean seed-20% old and 40% protein, and peanuts-50% oil and 30% protein, versus cereal grains-4% to 6% oil and 8% to 12% protein).

Hilum

Point of attachment of the seed to the legume pod. The seed receives its food during its growth and development through this attachment. The hilum may vary in color (ex. soybeans), thus providing one method of variety identification.

Micropyle

Point of entry of the pollen tube into the ovule as fertilization took place.

Radicle

The embryonic root found in the lower portion of the embryo axis. Upon germination and emergence it develops into the central axis of the root system.

Epicotyl

The embryonic shoot and leaves. It contains the growing point (apical meristem) and the first two (unifoliolate) leaves. The stem and future vegetative growth forms from the growing point.

Pod

The legume pod is the developed ovary that encloses the seeds (mature, fertilized ovules). Thus, legume seeds are botanically true seeds because they are separated from the pod (ovary tissue) when threshed and harvested.

Hypocotyl

The stem tissue between the epicotyl and the radicle. In most legumes the hypocotyl elongates during germination to cause emergence of the seedling.

Testa

The true seed coat of a legume seed. The testa develops from the fertilized ovule and acts as protective tissue for the internal seed parts.

Embryo Area

This is the area of the embryo axis which develops into the legume seedling and is in a very vulnerable position for mechanical damage. Therefore, seeds should be handled as gently as possible in threshing and conditioning.